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1.
  • Abdelaziz, Omar Y., et al. (författare)
  • Biological valorization of low molecular weight lignin
  • 2016
  • Ingår i: Biotechnology Advances. - : Elsevier BV. - 0734-9750. ; 34:8, s. 1318-1346
  • Forskningsöversikt (refereegranskat)abstract
    • Lignin is a major component of lignocellulosic biomass and as such, it is processed in enormous amounts in the pulp and paper industry worldwide. In such industry it mainly serves the purpose of a fuel to provide process steam and electricity, and to a minor extent to provide low grade heat for external purposes. Also from other biorefinery concepts, including 2nd generation ethanol, increasing amounts of lignin will be generated. Other uses for lignin – apart from fuel production – are of increasing interest not least in these new biorefinery concepts. These new uses can broadly be divided into application of the polymer as such, native or modified, or the use of lignin as a feedstock for the production of chemicals. The present review focuses on the latter and in particular the advances in the biological routes for chemicals production from lignin. Such a biological route will likely involve an initial depolymerization, which is followed by biological conversion of the obtained smaller lignin fragments. The conversion can be either a short catalytic conversion into desired chemicals, or a longer metabolic conversion. In this review, we give a brief summary of sources of lignin, methods of depolymerization, biological pathways for conversion of the lignin monomers and the analytical tools necessary for characterizing and evaluating key lignin attributes.
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2.
  • Abdelaziz, Omar Y., et al. (författare)
  • Oxidative Depolymerization of Kraft Lignin for Microbial Conversion
  • 2019
  • Ingår i: ACS Sustainable Chemistry and Engineering. - : American Chemical Society (ACS). - 2168-0485. ; 7:13, s. 11640-11652
  • Tidskriftsartikel (refereegranskat)abstract
    • The valorization of lignin is being increasingly recognized as crucial to improve the economic viability of integrated biorefineries. Because of its inherent heterogeneity and recalcitrance, lignin has been treated as a waste product in the pulp and paper industry, but new technologies are now being explored to transform lignin into a sustainable resource and enhance its value chain. In the present study, alkaline oxidative depolymerization was investigated as a potential form of pretreatment to enable further biological conversion of LignoBoost kraft lignin (LB). LB lignin oxidation reactions were studied at various temperatures (120-200 °C) and O2 partial pressures (3-15 bar) to identify the optimal conditions for obtaining a biocompatible, oxidatively depolymerized lignin (ODLB) stream. The low molecular weight compounds resulting from this treatment consisted mainly of aromatic monomers and carboxylic acids. The highest yield of aromatic monomers, 3 wt %, was obtained at 160 °C and 3 bar O2. The yield of carboxylic acids increased with both increasing temperature and O2 pressure, exceeding 13% under the harshest conditions investigated. The growth of four aromatic-catabolizing bacterial strains was examined on reaction product mixtures, all of which showed growth on agar plates utilizing ODLB as the sole source of carbon and energy. Rhodococcus opacus and Sphingobium sp. SYK-6 were found to consume most of the aromatic monomers present in the ODLB (e.g., vanillin, vanillate, acetovanillone, and guaiacol). The findings of this study indicate that pretreatment by oxidative depolymerization has potential in the biological valorization of technical lignin streams, for the production of valuable chemicals and materials.
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4.
  • Albers, E, et al. (författare)
  • Continuous estimation of product concentration with calorimetry and gas analysis during anaerobic fermentations of Saccharomyces cerevisiae
  • 2002
  • Ingår i: Thermochimica Acta. - 0040-6031. ; 394:1-2, s. 185-190
  • Tidskriftsartikel (refereegranskat)abstract
    • Product concentrations may be estimated from gas analysis or calorimetric measurements. These techniques of analysis are fast, simple, and provide a continuous output. To check the accuracy of these estimations, the anaerobic ethanol formation of an industrial strain of the yeast Saccharomyces cerevisiae was selected as a test system. Cultivations were carried out as batch cultures with different nitrogen sources (ammonium, glutamate and a mixture of amino acids) and 20 g/l of glucose as the carbon and energy source. The results showed that there was a good agreement between measured and calculated ethanol values. However, especially when using heat data the results are very sensitive to small changes in the stoichiometry of the catabolic reaction, i.e. ethanol is not the only product but there are also minor amounts of glycerol and acetate. The problems generated by these products when using heat data to calculate ethanol concentrations are discussed in detail. (C) 2002 Elsevier Science B.V. All rights reserved.
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9.
  • Alkasrawi, Malek, et al. (författare)
  • Influence of strain and cultivation procedure on the performance of simultaneous saccharification and fermentation of steam pretreated spruce
  • 2006
  • Ingår i: Enzyme and Microbial Technology. - : Elsevier BV. - 0141-0229. ; 38:1-2, s. 279-286
  • Tidskriftsartikel (refereegranskat)abstract
    • Yeast to be used in simultaneous saccharification and fermentation (SSF) of lignocelluloses materials has to be prepared in a separate cultivation step. The effects of the cultivation procedure on the performance of SSF of steam pretreated softwood were studied in the current work. The yeast used in the SSF was either directly commercially available Baker's yeast (as packaged yeast) or the same strain of yeast produced from the hydrolysate obtained in the pretreatment of the softwood material. A second strain of Saccharomyces cerevisiae TMB3000. isolated from spent sulphite liquor, was also compared with the commercial Baker's yeast. The strains were tested in SSF at substrate loads of 3, 5 and 8% dry weight of water insoluble material. Final ethanol yields were above 85% of the theoretical (based on the available hexoses) in all cases, except for the package yeast for the 8% substrate load, in which case the final yield was less than 65%. The cultivation procedure was found to have a significant impact on the performance during SSF, as well as in small-scale fermentations of hydrolysate liquor without solid material. The Baker's yeast cultivated on the hydrolysate from the steam pretreatment had in all cases a higher productivity, in particular at the highest substrate load. Cultivated Baker's yeast had a slightly higher productivity than TMB3000. The results suggest that the adaptation of the yeast to the inhibitors present in the medium is an important factor that must be considered in the design of SSF processes.
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10.
  • Almeida, Joao, et al. (författare)
  • Carbon fluxes of xylose-consuming Saccharomyces cerevisiae strains are affected differently by NADH and NADPH usage in HMF reduction.
  • 2009
  • Ingår i: Applied Microbiology and Biotechnology. - : Springer Science and Business Media LLC. - 1432-0614 .- 0175-7598. ; 84, s. 751-761
  • Tidskriftsartikel (refereegranskat)abstract
    • Industrial Saccharomyces cerevisiae strains able to utilize xylose have been constructed by overexpression of XYL1 and XYL2 genes encoding the NADPH-preferring xylose reductase (XR) and the NAD(+)-dependent xylitol dehydrogenase (XDH), respectively, from Pichia stipitis. However, the use of different co-factors by XR and XDH leads to NAD(+) deficiency followed by xylitol excretion and reduced product yield. The furaldehydes 5-hydroxymethyl-furfural (HMF) and furfural inhibit yeast metabolism, prolong the lag phase, and reduce the ethanol productivity. Recently, genes encoding furaldehyde reductases were identified and their overexpression was shown to improve S. cerevisiae growth and fermentation rate in HMF containing media and in lignocellulosic hydrolysate. In the current study, we constructed a xylose-consuming S. cerevisiae strain using the XR/XDH pathway from P. stipitis. Then, the genes encoding the NADH- and the NADPH-dependent HMF reductases, ADH1-S110P-Y295C and ADH6, respectively, were individually overexpressed in this background. The performance of these strains, which differed in their co-factor usage for HMF reduction, was evaluated under anaerobic conditions in batch fermentation in absence or in presence of HMF. In anaerobic continuous culture, carbon fluxes were obtained for simultaneous xylose consumption and HMF reduction. Our results show that the co-factor used for HMF reduction primarily influenced formation of products other than ethanol, and that NADH-dependent HMF reduction influenced product formation more than NADPH-dependent HMF reduction. In particular, NADH-dependent HMF reduction contributed to carbon conservation so that biomass was produced at the expense of xylitol and glycerol formation.
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11.
  • Almeida, Joao, et al. (författare)
  • Increased tolerance and conversion of inhibitors in lignocellulosic hydrolysates by Saccharomyces cerevisiae
  • 2007
  • Ingår i: Journal of Chemical Technology and Biotechnology. - : Wiley. - 0268-2575 .- 1097-4660. ; 82:4, s. 340-349
  • Forskningsöversikt (refereegranskat)abstract
    • During hydrolysis of lignocellulosic biomass, monomeric sugars and a broad range of inhibitory compounds are formed and released. These inhibitors, which can be organized around three main groups, furans, weak acids and phenolics, reduce ethanol yield and productivity by affecting the microorganism performance during the fermentation step. Among the microorganisms that have been evaluated for lignocellulosic hydrolysate ethanol fermentation, the yeast Saccharomyces cerevisiae appears to be the least sensitive. In order to overcome the effect of inhibitors, strategies that include improvement of natural tolerance of microorganism and use of fermentation control strategies have been developed. An overview of the origin, effects and mechanisms of action of known inhibitors on S. cerevisiae is given. Fermentation control strategies as well as metabolic, genetic and evolutionary engineering strategies to obtain S. cerevisiae strains with improved tolerance are discussed.
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12.
  • Almeida, Joao, et al. (författare)
  • Metabolic effects of furaldehydes and impacts on biotechnological processes.
  • 2009
  • Ingår i: Applied Microbiology and Biotechnology. - : Springer Science and Business Media LLC. - 1432-0614 .- 0175-7598. ; 82:4, s. 625-638
  • Forskningsöversikt (refereegranskat)abstract
    • There is a growing awareness that lignocellulose will be a major raw material for production of both fuel and chemicals in the coming decades-most likely through various fermentation routes. Considerable attention has been given to the problem of finding efficient means of separating the major constituents in lignocellulose (i.e., lignin, hemicellulose, and cellulose) and to efficiently hydrolyze the carbohydrate parts into sugars. In these processes, by-products will inevitably form to some extent, and these will have to be dealt with in the ensuing microbial processes. One group of compounds in this category is the furaldehydes. 2-Furaldehyde (furfural) and substituted 2-furaldehydes-most importantly 5-hydroxymethyl-2-furaldehyde-are the dominant inhibitory compounds found in lignocellulosic hydrolyzates. The furaldehydes are known to have biological effects and act as inhibitors in fermentation processes. The effects of these compounds will therefore have to be considered in the design of biotechnological processes using lignocellulose. In this short review, we take a look at known metabolic effects, as well as strategies to overcome problems in biotechnological applications caused by furaldehydes.
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13.
  • Almeida, Joao, et al. (författare)
  • NADH- vs NADPH-coupled reduction of 5-hydroxymethyl furfural (HMF) and its implications on product distribution in Saccharomyces cerevisiae.
  • 2008
  • Ingår i: Applied Microbiology and Biotechnology. - : Springer Science and Business Media LLC. - 1432-0614 .- 0175-7598. ; 78:6, s. 939-945
  • Tidskriftsartikel (refereegranskat)abstract
    • Saccharomyces cerevisiae alcohol dehydrogenases responsible for NADH-, and NADPH-specific reduction of the furaldehydes 5-hydroxymethyl-furfural (HMF) and furfural have previously been identified. In the present study, strains overexpressing the corresponding genes (mut-ADH1 and ADH6), together with a control strain, were compared in defined medium for anaerobic fermentation of glucose in the presence and absence of HMF. All strains showed a similar fermentation pattern in the absence of HMF. In the presence of HMF, the strain overexpressing ADH6 showed the highest HMF reduction rate and the highest specific ethanol productivity, followed by the strain overexpressing mut-ADH1. This correlated with in vitro HMF reduction capacity observed in the ADH6 overexpressing strain. Acetate and glycerol yields per biomass increased considerably in the ADH6 strain. In the other two strains, only the overall acetate yield per biomass was affected. When compared in batch fermentation of spruce hydrolysate, strains overexpressing ADH6 and mut-ADH1 had five times higher HMF uptake rate than the control strain and improved specific ethanol productivity. Overall, our results demonstrate that (1) the cofactor usage in the HMF reduction affects the product distribution, and (2) increased HMF reduction activity results in increased specific ethanol productivity in defined mineral medium and in spruce hydrolysate.
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14.
  • Almeida, Joao, et al. (författare)
  • Pichia stipitis xylose reductase helps detoxifying lignocellulosic hydrolysate by reducing 5-hydroxymethyl-furfural (HMF)
  • 2008
  • Ingår i: Biotechnology for Biofuels. - : Springer Science and Business Media LLC. - 1754-6834. ; 1
  • Tidskriftsartikel (refereegranskat)abstract
    • Background: Pichia stipitis xylose reductase (Ps-XR) has been used to design Saccharomyces cerevisiae strains that are able to ferment xylose. One example is the industrial S. cerevisiae xyloseconsuming strain TMB3400, which was constructed by expression of P. stipitis xylose reductase and xylitol dehydrogenase and overexpression of endogenous xylulose kinase in the industrial S. cerevisiae strain USM21. Results: In this study, we demonstrate that strain TMB3400 not only converts xylose, but also displays higher tolerance to lignocellulosic hydrolysate during anaerobic batch fermentation as well as 3 times higher in vitro HMF and furfural reduction activity than the control strain USM21. Using laboratory strains producing various levels of Ps-XR, we confirm that Ps-XR is able to reduce HMF both in vitro and in vivo. Ps-XR overexpression increases the in vivo HMF conversion rate by approximately 20%, thereby improving yeast tolerance towards HMF. Further purification of Ps-XR shows that HMF is a substrate inhibitor of the enzyme. Conclusion: We demonstrate for the first time that xylose reductase is also able to reduce the furaldehyde compounds that are present in undetoxified lignocellulosic hydrolysates. Possible implications of this newly characterized activity of Ps-XR on lignocellulosic hydrolysate fermentation are discussed.
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15.
  • Almeida, João R.M., et al. (författare)
  • Physiological and Molecular Characterization of Yeast Cultures Pre-Adapted for Fermentation of Lignocellulosic Hydrolysate
  • 2023
  • Ingår i: Fermentation. - : MDPI AG. - 2311-5637. ; 9:1
  • Tidskriftsartikel (refereegranskat)abstract
    • Economically feasible bioethanol process from lignocellulose requires efficient fermentation by yeast of all sugars present in the hydrolysate. However, when exposed to lignocellulosic hydrolysate, Saccharomyces cerevisiae is challenged with a variety of inhibitors that reduce yeast viability, growth, and fermentation rate, and in addition damage cellular structures. In order to evaluate the capability of S. cerevisiae to adapt and respond to lignocellulosic hydrolysates, the physiological effect of cultivating yeast in the spruce hydrolysate was comprehensively studied by assessment of yeast performance in simultaneous saccharification and fermentation (SSF), measurement of furaldehyde reduction activity, assessment of conversion of phenolic compounds and genome-wide transcription analysis. The yeast cultivated in spruce hydrolysate developed a rapid adaptive response to lignocellulosic hydrolysate, which significantly improved its fermentation performance in subsequent SSF experiments. The adaptation was shown to involve the induction of NADPH-dependent aldehyde reductases and conversion of phenolic compounds during the fed-batch cultivation. These properties were correlated to the expression of several genes encoding oxidoreductases, notably AAD4, ADH6, OYE2/3, and YML131w. The other most significant transcriptional changes involved genes involved in transport mechanisms, such as YHK8, FLR1, or ATR1. A large set of genes were found to be associated with transcription factors (TFs) involved in stress response (Msn2p, Msn4p, Yap1p) but also cell growth and division (Gcr4p, Ste12p, Sok2p), and these TFs were most likely controlling the response at the post-transcriptional level.
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16.
  • Almeida, Joao, et al. (författare)
  • Stress-related challenges in pentose fermentation to ethanol by the yeast Saccharomyces cerevisiae.
  • 2011
  • Ingår i: Biotechnology Journal. - : Wiley. - 1860-6768. ; 6, s. 286-299
  • Forskningsöversikt (refereegranskat)abstract
    • Conversion of agricultural residues, energy crops and forest residues into bioethanol requires hydrolysis of the biomass and fermentation of the released sugars. During the hydrolysis of the hemicellulose fraction, substantial amounts of pentose sugars, in particular xylose, are released. Fermentation of these pentose sugars to ethanol by engineered Saccharomyces cerevisiae under industrial process conditions is the subject of this review. First, fermentation challenges originating from the main steps of ethanol production from lignocellulosic feedstocks are discussed, followed by genetic modifications that have been implemented in S. cerevisiae to obtain xylose and arabinose fermenting capacity per se. Finally, the fermentation of a real lignocellulosic medium is discussed in terms of inhibitory effects of furaldehydes, phenolics and weak acids and the presence of contaminating microbiota.
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18.
  • Almqvist, Henrik, et al. (författare)
  • Characterization of the Weimberg Pathway in Caulobacter crescentus
  • 2018
  • Ingår i: Fermentation. - : MDPI AG. - 2311-5637. ; 4:2
  • Tidskriftsartikel (refereegranskat)abstract
    • Caulobacter crescentus is a gram-negative bacterium that can utilize xylose as a substrate using the Weimberg pathway, which converts xylose to α-ketoglutarate in five steps without carbon loss. This is an interesting pathway for heterologous expression in other organisms in order to enable xylose utilization in biorefinery processes. C. crescentus was grown on xylose, arabinose and glucose, and maximum specific growth rates determined for the three substrates were 0.11 h−1, 0.05 h−1, and 0.15 h−1 respectively. Growth was found to be significantly inhibited at sugar concentration of 20 g L−1, shown primarily by an increased lag phase. Enzyme activity assays showed that the Weimberg pathway was active in cells grown, not only on xylose but also on arabinose. No activity was found for growth on glucose. Furthermore, substantial amounts of α-ketoglutarate—up to a yield of 0.4 g g−1—was excreted during growth on xylose, but no other extracellular intermediates in the Weimberg pathway were detected during growth on xylose. Apparently, C. crescentus is not well adapted for efficient growth on high xylose levels, and responds by an extended lag phase and secretion of α-ketoglutarate.
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19.
  • Almqvist, Henrik, et al. (författare)
  • Succinic acid production by Actinobacillus succinogenes from batch fermentation of mixed sugars
  • 2016
  • Ingår i: Journal of Industrial Microbiology & Biotechnology. - : Oxford University Press (OUP). - 1367-5435 .- 1476-5535. ; 43:8, s. 1117-1130
  • Tidskriftsartikel (refereegranskat)abstract
    • Succinic acid production from the monosaccharides xylose, arabinose, glucose, mannose and galactose was studied using the bacterium Actinobacillus succinogenes. In Duran bottle cultures, containing 10 g/L of each of sugar, succinic acid was produced from all sugars except for galactose. The highest succinate yield, 0.56 g/g, was obtained with glucose, whereas the succinate yield was 0.42, 0.38 and 0.44 g/g for xylose, mannose and arabinose, respectively. The specific succinate productivity was 0.7 g/g h for glucose, but below 0.2 g/g h for the other sugars. Batch bioreactor fermentations were carried out using a sugar mixture of the five sugars giving a total concentration of 50 g/L, mimicking the distribution of sugars in spent sulfite liquor (SSL) from Eucalyptus which is rich in xylose. In this mixture, an almost complete conversion of all sugars (except galactose) was achieved resulting in a final succinate concentration of 21.8–26.8 g/L and a total yield of 0.59–0.68 g/g. There was evidence of co-consumption of glucose and xylose, whereas mannose was consumed after glucose. The main by-products were acetate 0.14–0.20 g/g and formate 0.08–0.13 g/g. NADH balance calculations suggested that NADH required for succinate production was not met solely from formate and acetate production, but other means of NADH production was necessary. Results from mixed sugar fermentations were verified using SSL as substrate resulting in a succinate yield of 0.60 g/g. In addition, it was found that CO2 sparging could replace carbonate supply in the form of MgCO3 without affecting the succinate yield.
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20.
  • Alvarez, Rene, et al. (författare)
  • Anaerobic co-digestion of aquatic flora and quinoa with manures from Bolivian Altiplano
  • 2008
  • Ingår i: Waste Management: international journal of integrated waste management, science and technology. - : Elsevier BV. - 1879-2456. ; 28:10, s. 1933-1940
  • Tidskriftsartikel (refereegranskat)abstract
    • Quinoa stalk (Chenopodium quinoa Willd.) from agricultural crop residue, totora (Schoenoplectus tatora) and o-macrophytes (aquatic flora) from Lake Titicaca (on the Bolivian Altiplano) were studied in a wet anaerobic co-digestion process together with manure front llama, cow and sheep. Anaerobic semi-continuous experiments were performed in (10) 2-1 reactors at a temperature of 25 degrees C with 30 days of hydraulic retention time (HRT) and ail organic loading rate (OLR) of 1.8 kg VS m(-3) d(-1). Totora was found to be the best co-substrate. In mixture ratios of 1:1 (VS basis), it increased the biogas productivity by 130% for llama manure, 60% for cow manure, and 40% for sheep manure. It was possible to use up to 58% (VS basis) of totora in the substrate. Higher concentrations (including pure totora) could not be digested, as that caused acidification problems similar to those caused by other lignocellulosic materials. When quinoa and o-macrophytes were used as co-substrates, the increase in biogas productivity was slightly less. However, these co-substrates did not cause any operational problems. An additional advantage of quinoa and o-macrophytes was that they could be used in any proportion (even in pure form) without causing any destabilization problems in the anaerobic digestion process. (C) 2007 Elsevier Ltd. All rights reserved.
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21.
  • Alvarez, Rene, et al. (författare)
  • Biogas production from llama and cow manure at high altitude
  • 2006
  • Ingår i: Biomass & Bioenergy. - : Elsevier BV. - 1873-2909 .- 0961-9534. ; 30:1, s. 66-75
  • Tidskriftsartikel (refereegranskat)abstract
    • Methane production from llama and cow manures from the Bolivian high plateau (The "Altiplano") was studied using a parallel reactor set-up consisting of 10 lab-scale biogasifiers. The effects of pressure (495 and 760 mmHg), temperature (11 and 35 degrees C), hydraulic retention time (20 and 50 days), and manure content in the slurry (10%, 20% and 50%) were evaluated with respect to productivity and methane yields based on two 2(4-1) fractional factorial designs with 8 treatments for each kind of manure. The reactors were operated semi-continuously with daily manure feeding for periods between 50 and 100 days. Temperature was the main factor effect found, and the hydraulic retention time and the manure content in feed were also found significant whereas the effect of pressure was not significant in the range studied. The methane yield obtained with cow manure at 11 degrees C was between 6.4 and 33.61 CH4 kg(-1) VS (volatile solids added) whereas at 35 degrees C the methane yield was between 49.6 and 131.31 CH4 kg(-1) VS. The methane yield from llama manure was somewhat lower than for cow manure (between 3.3 and 19.31 CH4 kg(-1) VS at 11 degrees C and between 35.6 and 84.11 CH4 kg(-1) VS at 35 degrees C, respectively). However, overall llama manure was found to be the best raw material of the two for biogas production, due to its high content of volatile solid-higher than has been previously reported for most manures-and also its high nitrogen and phosphorous content.
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22.
  • Alvarez, Rene, et al. (författare)
  • Low temperature anaerobic digestion of mixtures of llama, cow and sheep manure for improved methane production
  • 2009
  • Ingår i: Biomass & Bioenergy. - : Elsevier BV. - 1873-2909 .- 0961-9534. ; 33:3, s. 527-533
  • Tidskriftsartikel (refereegranskat)abstract
    • Biogas production in anaerobic digestion in farm-scale units is typically performed under mesophilic conditions when used for producing domestic fuel and stabilizing animal waste for the use of digested manure as a fertilizer. Previous studies on the digestion of llama and cow manure have shown the feasibility of producing biogas under altiplano conditions (low pressure and low temperature) and of llama manure as a promising feedstock. The present study concerns the utilization of various mixtures of feedstocks from the Bolivian altiplano under low temperature conditions (18-25 degrees C). Laboratory scale experiments were performed on the digestion of mixtures of llama, sheep and cow manure in a semi-continuous process using ten 2-L stainless steel digesters to determine the effects of organic loading rate (OLR) and the feed composition. The semi-continuous operation of mixture of llama-cow-sheep manure proved to be a reliable system, which could be operated with good stability. The results suggest that in a system digesting a mixture of llama-cow-sheep manure at low temperature (18-25 degrees C) the maximum OLR value is between 4 and 6 kg VS m(3) d(-1). The methane yields obtained in the mixture experiments were in the range 0.07-0.14 m(3) kg(-1) VS added, with a methane concentration in the gas of between 47 and 55%. (C) 2008 Elsevier Ltd. All rights reserved.
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23.
  • Alvarez, Rene, et al. (författare)
  • Semi-continuous co-digestion of solid slaughterhouse waste, manure, and fruit and vegetable waste
  • 2008
  • Ingår i: Renewable Energy. - : Elsevier BV. - 0960-1481. ; 33:4, s. 726-734
  • Tidskriftsartikel (refereegranskat)abstract
    • The potential of semi-continuous mesophilic anaerobic digestion (AD) for the treatment of solid slaughterhouse waste, fruit-vegetable wastes, and manure in a co-digestion process has been experimentally evaluated. A study was made at laboratory scale using four 2 L reactors working semi-continuously at 35 degrees C. The effect of the organic loading rate (OLR) was initially examined (using equal proportion of the three components on a volatile solids, VS, basis). Anaerobic co-digestion with OLRs in the range 0.3-1.3 kg VS m(-3) d(-1) resulted in methane yields of 0.3 m(3) kg(-1) VS added, with a methane content in the biogas of 54-56%. However, at a further increased loading, the biogas production decreased and there was a reduction in the methane yield indicating organic overload or insufficient buffering capacity in the digester. In the second part of the investigation, co-digestion was studied in a mixture experiment using 10 different feed compositions. The digestion of mixed substrates was in all cases better than that of the pure substrates, with the exception of the mixture of equal amounts of (VS/VS) solid cattle-swine slaughterhouse waste (SCSSW) with fruit and vegetable waste (FVW). For all other mixtures, the steady-state biogas production for the mixture was in the range 1.1-1.6 L d(-1), with a methane content of 50-57% after 60 days of operation. The methane yields were in the range 0.27-0.35 m(3) kg(-1) VS added and VS reductions of more than 50% and up to 67% were obtained.
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24.
  • Alvarez, Rene, et al. (författare)
  • The effect of temperature variation on biomethanation at high altitude.
  • 2008
  • Ingår i: Bioresource Technology. - : Elsevier BV. - 1873-2976 .- 0960-8524. ; 99, s. 7278-7284
  • Tidskriftsartikel (refereegranskat)abstract
    • The aim of the current study was to examine effects of daily temperature variations on the performance of anaerobic digestion. Forced square-wave temperature variations (between 11 and 25, 15 and 28, and 19 and 32 degrees C) were imposed on a bench-scale digester using a mixture of llama-cow-sheep manure in a semi-continuous process. The volumetric biogas production rate, methane yield, and the volatile solid reductions were compared with the results obtained from anaerobic digestion (AD) at constant temperatures. The forced cyclic variations of temperature caused large cyclic variations in the rate of gas production and the methane content. As much as 94-97% of the daily biogas was obtained in the 12h half-cycle at high temperature. The values for volumetric biogas production rate and methane yield increased at higher temperatures. The average volumetric biogas production rate for cyclic operation between 11 and 25 degrees C was 0.22Ld(-1)L(-1) with a yield of 0.07m(3)CH(4)kg(-1) VS added (VSadd), whereas for operation between 15 and 29 degrees C the volumetric biogas production rate increased by 25% (to 0.27Ld(-1)L(-1) with a yield of 0.08m(3)CH(4)kg(-1) VSadd). In the highest temperature region a further increase of 7% in biogas production was found and the methane yield was 0.089m(3)CH(4)kg(-1) VSadd. The employed digester showed an immediate response when the temperature was elevated, which indicates a well-maintained metabolic capacity of the methanogenic bacteria during the period of low temperature. Overall, periodic temperature variations appear to give less decrease in process performance than a priori anticipated.
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25.
  • Alvfors, Per, 1954-, et al. (författare)
  • Research and development challenges for Swedish biofuel actors – three illustrative examples : Improvement potential discussed in the context of Well-to-Tank analyses
  • 2010
  • Rapport (övrigt vetenskapligt/konstnärligt)abstract
    • Currently biofuels have strong political support, both in the EU and Sweden. The EU has, for example, set a target for the use of renewable fuels in the transportation sector stating that all EU member states should use 10% renewable fuels for transport by 2020. Fulfilling this ambition will lead to an enormous market for biofuels during the coming decade. To avoid increasing production of biofuels based on agriculture crops that require considerable use of arable area, focus is now to move towards more advanced second generation (2G) biofuels that can be produced from biomass feedstocks associated with a more efficient land use. Climate benefits and greenhouse gas (GHG) balances are aspects often discussed in conjunction with sustainability and biofuels. The total GHG emissions associated with production and usage of biofuels depend on the entire fuel production chain, mainly the agriculture or forestry feedstock systems and the manufacturing process. To compare different biofuel production pathways it is essential to conduct an environmental assessment using the well-to-tank (WTT) analysis methodology. In Sweden the conditions for biomass production are favourable and we have promising second generation biofuels technologies that are currently in the demonstration phase. In this study we have chosen to focus on cellulose based ethanol, methane from gasification of solid wood as well as DME from gasification of black liquor, with the purpose of identifying research and development potentials that may result in improvements in the WTT emission values. The main objective of this study is thus to identify research and development challenges for Swedish biofuel actors based on literature studies as well as discussions with the the researchers themselves. We have also discussed improvement potentials for the agriculture and forestry part of the WTT chain. The aim of this study is to, in the context of WTT analyses, (i) increase knowledge about the complexity of biofuel production, (ii) identify and discuss improvement potentials, regarding energy efficiency and GHG emissions, for three biofuel production cases, as well as (iii) identify and discuss improvement potentials regarding biomass supply, including agriculture/forestry. The scope of the study is limited to discussing the technologies, system aspects and climate impacts associated with the production stage. Aspects such as the influence on biodiversity and other environmental and social parameters fall beyond the scope of this study. We find that improvement potentials for emissions reductions within the agriculture/forestry part of the WTT chain include changing the use of diesel to low-CO2-emitting fuels, changing to more fuel-efficient tractors, more efficient cultivation and manufacture of fertilizers (commercial nitrogen fertilizer can be produced in plants which have nitrous oxide gas cleaning) as well as improved fertilization strategies (more precise nitrogen application during the cropping season). Furthermore, the cultivation of annual feedstock crops could be avoided on land rich in carbon, such as peat soils and new agriculture systems could be introduced that lower the demand for ploughing and harrowing. Other options for improving the WTT emission values includes introducing new types of crops, such as wheat with higher content of starch or willow with a higher content of cellulose. From the case study on lignocellulosic ethanol we find that 2G ethanol, with co-production of biogas, electricity, heat and/or wood pellet, has a promising role to play in the development of sustainable biofuel production systems. Depending on available raw materials, heat sinks, demand for biogas as vehicle fuel and existing 1G ethanol plants suitable for integration, 2G ethanol production systems may be designed differently to optimize the economic conditions and maximize profitability. However, the complexity connected to the development of the most optimal production systems require improved knowledge and involvement of several actors from different competence areas, such as chemical and biochemical engineering, process design and integration and energy and environmental systems analysis, which may be a potential barrier.
  •  
26.
  • Alvfors, Per, et al. (författare)
  • Research and development challenges for Swedish biofuel actors – three illustrative examples
  • 2010
  • Rapport (övrigt vetenskapligt/konstnärligt)abstract
    • Currently biofuels have strong political support, both in the EU and Sweden. The EU has, for example, set a target for the use of renewable fuels in the transportation sector stating that all EU member states should use 10% renewable fuels for transport by 2020. Fulfilling this ambition will lead to an enormous market for biofuels during the coming decade. To avoid increasing production of biofuels based on agriculture crops that require considerable use of arable area, focus is now to move towards more advanced second generation (2G) biofuels that can be produced from biomass feedstocks associated with a more efficient land use.Climate benefits and greenhouse gas (GHG) balances are aspects often discussed in conjunction with sustainability and biofuels. The total GHG emissions associated with production and usage of biofuels depend on the entire fuel production chain, mainly the agriculture or forestry feedstock systems and the manufacturing process. To compare different biofuel production pathways it is essential to conduct an environmental assessment using the well-to-tank (WTT) analysis methodology. In Sweden the conditions for biomass production are favourable and we have promising second generation biofuels technologies that are currently in the demonstration phase. In this study we have chosen to focus on cellulose based ethanol, methane from gasification of solid wood as well as DME from gasification of black liquor, with the purpose of identifying research and development potentials that may result in improvements in the WTT emission values. The main objective of this study is thus to identify research and development challenges for Swedish biofuel actors based on literature studies as well as discussions with the the researchers themselves. We have also discussed improvement potentials for the agriculture and forestry part of the WTT chain. The aim of this study is to, in the context of WTT analyses, (i) increase knowledge about the complexity of biofuel production, (ii) identify and discuss improvement potentials, regarding energy efficiency and GHG emissions, for three biofuel production cases, as well as (iii) identify and discuss improvement potentials regarding biomass supply, including agriculture/forestry. The scope of the study is limited to discussing the technologies, system aspects and climate impacts associated with the production stage. Aspects such as the influence on biodiversity and other environmental and social parameters fall beyond the scope of this study. We find that improvement potentials for emissions reductions within the agriculture/forestry part of the WTT chain include changing the use of diesel to low-CO2-emitting fuels, changing to more fuel-efficient tractors, more efficient cultivation and manufacture of fertilizers (commercial nitrogen fertilizer can be produced in plants which have nitrous oxide gas cleaning) as well as improved fertilization strategies (more precise nitrogen application during the cropping season). Furthermore, the cultivation of annual feedstock crops could be avoided on land rich in carbon, such as peat soils and new agriculture systems could be introduced that lower the demand for ploughing and harrowing. Other options for improving the WTT emission values includes introducing new types of crops, such as wheat with higher content of starch or willow with a higher content of cellulose. From the case study on lignocellulosic ethanol we find that 2G ethanol, with co-production of biogas, electricity, heat and/or wood pellet, has a promising role to play in the development of sustainable biofuel production systems. Depending on available raw materials, heat sinks, demand for biogas as vehicle fuel and existing 1G ethanol plants suitable for integration, 2G ethanol production systems may be designed differently to optimize the economic conditions and maximize profitability. However, the complexity connected to the development of the most optimal production systems require improved knowledge and involvement of several actors from different competence areas, such as chemical and biochemical engineering, process design and integration and energy and environmental systems analysis, which may be a potential barrier. Three important results from the lignocellulosic ethanol study are: (i) the production systems could be far more complex and intelligently designed than previous studies show, (ii) the potential improvements consist of a large number of combinations of process integration options wich partly depends on specific local conditions, (iii) the environmental performance of individual systems may vary significantly due to systems design and local conditons.From the case study on gasification of solid biomass for the production of biomethane we find that one of the main advantages of this technology is its high efficiency in respect to converting biomass into fuels for transport. For future research we see a need for improvements within the gas up-grading section, including gas cleaning and gas conditioning, to obtain a more efficient process. A major challenge is to remove the tar before the methanation reaction. Three important results from the biomethane study are: (i) it is important not to crack the methane already produced in the syngas, which indicates a need for improved catalysts for selective tar cracking, (ii) there is a need for new gas separation techniques to facilitate the use of air oxidation agent instead of oxygen in the gasifier, and (iii) there is a need for testing the integrated process under realistic conditions, both at atmospheric and pressurized conditions. From the case study on black liquor gasification for the production of DME we find that the process has many advantages compared to other biofuel production options, such as the fact that black liquor is already partially processed and exists in a pumpable, liquid form, and that the process is pressurised and tightly integrated with the pulp mill, which enhances fuel production efficiency. However, to achieve commercial status, some challenges still remain, such as demonstrating that materials and plant equipment meet the high availability required when scaling up to industrial size in the pulp mill, and also proving that the plant can operate according to calculated heat and material balances. Three important results from the DME study are: (i) that modern chemical pulp mills, having a potential surplus of energy, could become important suppliers of renewable fuels for transport, (ii) there is a need to demonstrate that renewable DME/methanol will be proven to function in large scale, and (iii) there is still potential for technology improvements and enhanced energy integration. Although quantitative improvement potentials are given in the three biofuel production cases, it is not obvious how these potentials would affect WTT values, since the biofuel production processes are complex and changing one parameter impacts other parameters. The improvement potentials are therefore discussed qualitatively. From the entire study we have come to agree on the following common conclusions: (i) research and development in Sweden within the three studied 2G biofuel production technologies is extensive, (ii) in general, the processes, within the three cases, work well at pilot and demonstration scale and are now in a phase to be proven in large scale, (iii) there is still room for improvement although some processes have been known for decades, (iv) the biofuel production processes are complex and site specific and process improvements need to be seen and judged from a broad systems perspective (both within the production plant as well as in the entire well-to-tank perspective), and (v) the three studied biofuel production systems are complementary technologies. Futher, the process of conducting this study is worth mentioning as a result itself, i.e. that many different actors within the field have proven their ability and willingness to contribute to a common report, and that the cooperation climate was very positive and bodes well for possible future collaboration within the framework of the f3 center. Finally, judging from the political ambitions it is clear that the demand for renewable fuels will significantly increase during the coming decade. This will most likely result in opportunities for a range of biofuel options. The studied biofuel options all represent 2G biofuels and they can all be part of the solution to meet the increased renewable fuel demand.
  •  
27.
  • Alvors, Per, et al. (författare)
  • Research and development challenges for Swedish biofuel actors – three illustrative examples : Improvement potential discussed in the context of Well-to-Tank analyses
  • 2010
  • Rapport (övrigt vetenskapligt/konstnärligt)abstract
    • Currently biofuels have strong political support, both in the EU and Sweden. The EU has, for example, set a target for the use of renewable fuels in the transportation sector stating that all EU member states should use 10% renewable fuels for transport by 2020. Fulfilling this ambition will lead to an enormous market for biofuels during the coming decade. To avoid increasing production of biofuels based on agriculture crops that require considerable use of arable area, focus is now to move towards more advanced second generation (2G) biofuels that can be produced from biomass feedstocks associated with a more efficient land use.Climate benefits and greenhouse gas (GHG) balances are aspects often discussed in conjunction with sustainability and biofuels. The total GHG emissions associated with production and usage of biofuels depend on the entire fuel production chain, mainly the agriculture or forestry feedstock systems and the manufacturing process. To compare different biofuel production pathways it is essential to conduct an environmental assessment using the well-to-tank (WTT) analysis methodology.In Sweden the conditions for biomass production are favourable and we have promising second generation biofuels technologies that are currently in the demonstration phase. In this study we have chosen to focus on cellulose based ethanol, methane from gasification of solid wood as well as DME from gasification of black liquor, with the purpose of identifying research and development potentials that may result in improvements in the WTT emission values. The main objective of this study is thus to identify research and development challenges for Swedish biofuel actors based on literature studies as well as discussions with the the researchers themselves. We have also discussed improvement potentials for the agriculture and forestry part of the WTT chain. The aim of this study is to, in the context of WTT analyses, (i) increase knowledge about the complexity of biofuel production, (ii) identify and discuss improvement potentials, regarding energy efficiency and GHG emissions, for three biofuel production cases, as well as (iii) identify and discuss improvement potentials regarding biomass supply, including agriculture/forestry. The scope of the study is limited to discussing the technologies, system aspects and climate impacts associated with the production stage. Aspects such as the influence on biodiversity and other environmental and social parameters fall beyond the scope of this study.We find that improvement potentials for emissions reductions within the agriculture/forestry part of the WTT chain include changing the use of diesel to low-CO2-emitting fuels, changing to more fuel-efficient tractors, more efficient cultivation and manufacture of fertilizers (commercial nitrogen fertilizer can be produced in plants which have nitrous oxide gas cleaning) as well as improved fertilization strategies (more precise nitrogen application during the cropping season). Furthermore, the cultivation of annual feedstock crops could be avoided on land rich in carbon, such as peat soils and new agriculture systems could be introduced that lower the demand for ploughing and harrowing. Other options for improving the WTT emission values includes introducing new types of crops, such as wheat with higher content of starch or willow with a higher content of cellulose.From the case study on lignocellulosic ethanol we find that 2G ethanol, with co-production of biogas, electricity, heat and/or wood pellet, has a promising role to play in the development of sustainable biofuel production systems. Depending on available raw materials, heat sinks, demand for biogas as vehicle fuel and existing 1G ethanol plants suitable for integration, 2G ethanol production systems may be designed differently to optimize the economic conditions and maximize profitability. However, the complexity connected to the development of the most optimal production systems require improved knowledge and involvement of several actors from different competence areas, such as chemical and biochemical engineering, process design and integration and energy and environmental systems analysis, which may be a potential barrier.Three important results from the lignocellulosic ethanol study are: (i) the production systems could be far more complex and intelligently designed than previous studies show, (ii) the potential improvements consist of a large number of combinations of process integration options wich partly depends on specific local conditions, (iii) the environmental performance of individual systems may vary significantly due to systems design and local conditons.From the case study on gasification of solid biomass for the production of biomethane we find that one of the main advantages of this technology is its high efficiency in respect to converting biomass into fuels for transport. For future research we see a need for improvements within the gas up-grading section, including gas cleaning and gas conditioning, to obtain a more efficient process. A major challenge is to remove the tar before the methanation reaction.Three important results from the biomethane study are: (i) it is important not to crack the methane already produced in the syngas, which indicates a need for improved catalysts for selective tar cracking, (ii) there is a need for new gas separation techniques to facilitate the use of air oxidation agent instead of oxygen in the gasifier, and (iii) there is a need for testing the integrated process under realistic conditions, both at atmospheric and pressurized conditions.From the case study on black liquor gasification for the production of DME we find that the process has many advantages compared to other biofuel production options, such as the fact that black liquor is already partially processed and exists in a pumpable, liquid form, and that the process is pressurised and tightly integrated with the pulp mill, which enhances fuel production efficiency. However, to achieve commercial status, some challenges still remain, such as demonstrating that materials and plant equipment meet the high availability required when scaling up to industrial size in the pulp mill, and also proving that the plant can operate according to calculated heat and material balances. Three important results from the DME study are: (i) that modern chemical pulp mills, having a potential surplus of energy, could become important suppliers of renewable fuels for transport, (ii) there is a need to demonstrate that renewable DME/methanol will be proven to function in large scale, and (iii) there is still potential for technology improvements and enhanced energy integration.Although quantitative improvement potentials are given in the three biofuel production cases, it is not obvious how these potentials would affect WTT values, since the biofuel production processes are complex and changing one parameter impacts other parameters. The improvement potentials are therefore discussed qualitatively. From the entire study we have come to agree on the following common conclusions: (i) research and development in Sweden within the three studied 2G biofuel production technologies is extensive, (ii) in general, the processes, within the three cases, work well at pilot and demonstration scale and are now in a phase to be proven in large scale, (iii) there is still room for improvement although some processes have been known for decades, (iv) the biofuel production processes are complex and site specific and process improvements need to be seen and judged from a broad systems perspective (both within the production plant as well as in the entire well-to-tank perspective), and (v) the three studied biofuel production systems are complementary technologies. Futher, the process of conducting this study is worth mentioning as a result itself, i.e. that many different actors within the field have proven their ability and willingness to contribute to a common report, and that the cooperation climate was very positive and bodes well for possible future collaboration within the framework of the f3 center.Finally, judging from the political ambitions it is clear that the demand for renewable fuels will significantly increase during the coming decade. This will most likely result in opportunities for a range of biofuel options. The studied biofuel options all represent 2G biofuels and they can all be part of the solution to meet the increased renewable fuel demand.
  •  
28.
  • Arkitektur & teknik, Årskurs 2, et al. (författare)
  • På fötter genom England 2016
  • 2016
  • Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
    • Denna resedagbok är en del av Arkitektur och teknik-studenternas förberedelse för årskurs 3 och särskilt en träning i att söka, upptäcka och iakkta arkitekturens komplexa sammanhang och de värden som kan skapas genom arkitektur. Under studieresan byggs ett grundmaterial till dagboken upp genom förberedda presentationer, gemensamma analyser, undersökande skisser och konstnärliga övningar. Studieresan följs upp och bearbetas vid seminarier och genom korsläsning av texter där studenterna uppmanas till ett personligt reflekterande hållningssätt. På så sätt blir dagboken ett levande dokument som visar vår glädje och nyfikenhet över de många broar och byggnader vi upplevt tillsammans, och ett dokument som vill locka oss och alla läsare till vidare upptäcktsfärder.
  •  
29.
  • Ask, Magnus, 1983, et al. (författare)
  • A comparison between simultaneous saccharification and fermentation (SSF) and separate hydrolysis and fermentation (SHF) of spruce and giant reed using two Saccharomyces cerevisiae strains
  • 2010
  • Ingår i: Society for Industrial Microbiology, 60th annual meeting.
  • Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
    • For significant fermentative conversion of lignocellulose to ethanol, the yeast Saccharomyces cerevisiae has proved to be a robust organism, albeit inter-strain variations may have a big influence on process performance. In this study, two S. cerevisiae strains were evaluated for their ability to ferment two different lignocellulosic raw materials, giant reed and spruce at 10 % water insoluble solids (WIS). One industrial strain, Ethanol Red, and one laboratory strain carrying the XR/XDH pathway, VTT C-10880, were used. The process concept may also affect the choice of the most suitable strain. Therefore, two principal process concepts, simultaneous saccharification and fermentation (SSF) and separate hydrolysis and fermentation (SHF) were evaluated.The ethanol yield on giant reed based on total soluble sugars in the SHF was higher for VTT C-10880 than for Ethanol Red. On spruce, the yield of ethanol was higher for Ethanol Red. In SSF of giant reed, VTT C-10880 performed better in terms of the ethanol yield based on total sugars in fibres and liquid. However, the ethanol yield on spruce was higher for Ethanol Red than for VTT C-10880, which only produced a minor amount of ethanol. Spruce was more inhibitory than giant reed. Ethanol Red is more robust and converted the inhibitory substances in the pretreated materials faster, and is therefore a suitable industrial strain background for fermentation of both spruce and giant reed. Interestingly, VTT C-10880 performed better in SHF than SSF, primarily due to better xylose conversion in SHF.
  •  
30.
  • Ask, Magnus, 1983, et al. (författare)
  • Challenges in enzymatic hydrolysis and fermentation of pretreated Arundo donax revealed by a comparison between SHF and SSF
  • 2012
  • Ingår i: Process Biochemistry. - : Elsevier BV. - 1359-5113 .- 1873-3298. ; 47:10, s. 1452-1459
  • Tidskriftsartikel (refereegranskat)abstract
    • The perennial herbaceous crop Arundo donax is a potential feedstock for second-generation bioethanol production. In the present work, two different process options were investigated for the conversion of two differently steam-pretreated batches of A. donax. The pretreated raw material was converted to ethanol with a xylose-consuming Saccharomyces cerevisiae strain, VTT C-10880, by applying either separate hydrolysis and fermentation (SHF) or simultaneous saccharification and fermentation (SSF). The highest overall ethanol yield and final ethanol concentration were achieved using SHF (0.27 g g(-1) and 20.6 g L-1 compared to 0.24 g g(-1) and 19.0 g L-1 when SSF was used). The performance of both SHF and SSF was improved by complementing the cellulolytic enzymes with hemicellulases. The higher amount of acetic acid in one of the batches was shown to strongly affect xylose consumption in the fermentation. Only half of the xylose was consumed when batch 1 (high acetic acid) was fermented, compared to that 94% of the xylose was consumed in fermentation of batch 2 (lower acetic acid). Furthermore, the high amount of xylooligomers present in the pretreated materials considerably inhibited the enzymatic hydrolysis. Both the formation of xylooligomers and acetic acid thus need to be considered in the pretreatment process in order to achieve efficient conversion of A. donax to ethanol.
  •  
31.
  • Ask, Magnus, 1983, et al. (författare)
  • The effect of pretreatment harshness on separate hydrolysis and fermentation of giant reed by a xylose-consuming Saccharomyces cerevisiae strain
  • 2011
  • Ingår i: World Congress on Industrial Biotechnology and Bioprocessing, May 8 - 11, 2011, Toronto, Canada.
  • Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
    • Bioethanol produced from lignocellulosic feedstocks has received increased attention during the last years. To make lignocellulosic biomass susceptible to enzymatic hydrolysis, the materials first have to be pretreated. The pretreatment is often performed under harsh conditions, which release a number of compounds that can be inhibitory for enzymatic hydrolysis and the subsequent fermentation. Xylooligomers and acetic acid are two compounds that are potential inhibitors of enzymatic hydrolysis and fermentation, respectively. The final concentration of these compounds is highly dependent on the pretreatment conditions. In this study, two different pretreatments with different harshness were performed on giant reed. The influence of the resulting material composition on enzymatic hydrolysis was then investigated. The enzymatic hydrolysis was performed at 10 % (w/w) water insoluble solid concentration (WIS) with Celluclast 1.5L and Novozyme 188 with and without the addition of HTec which is acting on hemicellulose. During the harsher pretreatment, more xylooligomers were produced which were found to have a negative effect on the enzymatic hydrolysis. One of the hydrolysates contained a substantially higher concentration of acetic acid. To investigate the effect of this, the hydrolysed giant reed was fermented with a laboratory Saccharomyces cerevisiae strain, VTT C-10880, carrying the XR/XDH pathway. It was found that the acetic acid had a significant negative effect on the xylose consumption. By supplementing the less harsh pretreated material with the same amount of acetic acid, a similar decrease in xylose consumption was observed, indicating that acetic acid is limiting xylose fermentation in this case.
  •  
32.
  • Bengtsson, Andreas, 1988- (författare)
  • The effects of extramural language : Relationships between engagement in Japanese language activities and general Japanese language proficiency
  • 2023
  • Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • Many L2 learners believe they learn their target language by using it extramurally, i.e. outside the classroom. This topic, language learning as a result of engagement in L2 use, has garnered increased attention in the last decade. However, there is still a distinct lack of research. To date, most research offers snapshot studies of single groups of learners at similar L2 proficiency levels, and English is by far the most commonly researched target language.The present study quantitatively investigates the relationship between extramural Japanese and general Japanese language proficiency among adult learners studying at university in Sweden. It aims to do so both cross sectionally, using five different Levels of proficiency to investigate the moderating impact of proficiency at a macro level, and longitudinally, in order to move beyond correlations and provide empirical data on causal direction. In total, data were gathered from 168 individuals, many of whom participated in the study at different Levels, during a period of two and a half years. Data were analysed using non-parametric correlations and Bayesian regression.Results show that the participants engaged in extramural Japanese for considerable amounts of time every week. Some forms of Japanese language use (e.g. reading text and speaking face-to-face) related to general Japanese language proficiency, whereas others did not (e.g. listening to music and watching video with TL subtitles). These relationships were largely positive, although some relationships were negative or mixed. Proficiency level was a moderating factor, and different forms of language use had varying relationships with general Japanese language proficiency depending on participants’ Levels of study. In addition, the results suggest that extramural L2 use influenced proficiency but proficiency did not influence extramural L2 use. This is among the first studies to show such an effect empirically.Overall, the study makes significant contributions to our understanding of the connection between extramural L2 use and proficiency, which has implications on the applicability of results to other languages. Furthermore, the study also provides an innovative research framework for investigating extramural L2 use, which should be robust and valid for any target language.
  •  
33.
  • Bon, Elba, et al. (författare)
  • Yeasts in green chemistry
  • 2004
  • Ingår i: FEMS Yeast Research. - : Oxford University Press (OUP). - 1567-1364 .- 1567-1356. ; 5:3, s. 299-300
  • Tidskriftsartikel (refereegranskat)
  •  
34.
  • Borgström, Celina, et al. (författare)
  • Identification of modifications procuring growth on xylose in recombinant Saccharomyces cerevisiae strains carrying the Weimberg pathway
  • 2019
  • Ingår i: Metabolic Engineering. - : Elsevier BV. - 1096-7176. ; 55, s. 1-11
  • Tidskriftsartikel (refereegranskat)abstract
    • The most prevalent xylose-assimilating pathways in recombinant Saccharomyces cerevisiae, i.e. the xylose isomerase (XI) and the xylose reductase/xylitol dehydrogenase (XR/XDH) pathways, channel the carbon flux through the pentose phosphate pathway and further into glycolysis. In contrast, the oxidative and non-phosphorylative bacterial Weimberg pathway channels the xylose carbon through five steps into the metabolic node α-ketoglutarate (αKG) that can be utilized for growth or diverted into production of various metabolites. In the present study, steps preventing the establishment of a functional Weimberg pathway in S. cerevisiae were identified. Using an original design where a S. cerevisiae strain was expressing the essential four genes of the Caulobacter crescentus pathway (xylB, xylD, xylX, xylA) together with a deletion of FRA2 gene to upregulate the iron-sulfur metabolism, it was shown that the C. crescentus αKG semialdehyde dehydrogenase, XylA was not functional in S. cerevisiae. When replaced by the recently described analog from Corynebacterium glutamicum, KsaD, significantly higher in vitro activity was observed but the strain did not grow on xylose. Adaptive laboratory evolution (ALE) on a xylose/glucose medium on this strain led to a loss of XylB, the first step of the Weimberg pathway, suggesting that ALE favored minimizing the inhibiting xylonate accumulation by restricting the upper part of the pathway. Therefore three additional gene copies of the lower Weimberg pathway (XylD, XylX and KsaD) were introduced. The resulting S. cerevisiae strain (ΔΔfra2, xylB, 4x (xylD-xylX-ksaD)) was able to generate biomass from xylose and Weimberg pathway intermediates were detected. To our knowledge this is the first report of a functional complete Weimberg pathway expressed in fungi. When optimized this pathway has the potential to channel xylose towards value-added specialty chemicals such as dicarboxylic acids and diols.
  •  
35.
  • Brink, Daniel P., et al. (författare)
  • Mapping the diversity of microbial lignin catabolism : experiences from the eLignin database
  • 2019
  • Ingår i: Applied Microbiology and Biotechnology. - : Springer Science and Business Media LLC. - 0175-7598 .- 1432-0614. ; , s. 3979-4002
  • Forskningsöversikt (refereegranskat)abstract
    • Lignin is a heterogeneous aromatic biopolymer and a major constituent of lignocellulosic biomass, such as wood and agricultural residues. Despite the high amount of aromatic carbon present, the severe recalcitrance of the lignin macromolecule makes it difficult to convert into value-added products. In nature, lignin and lignin-derived aromatic compounds are catabolized by a consortia of microbes specialized at breaking down the natural lignin and its constituents. In an attempt to bridge the gap between the fundamental knowledge on microbial lignin catabolism, and the recently emerging field of applied biotechnology for lignin biovalorization, we have developed the eLignin Microbial Database (www.elignindatabase.com), an openly available database that indexes data from the lignin bibliome, such as microorganisms, aromatic substrates, and metabolic pathways. In the present contribution, we introduce the eLignin database, use its dataset to map the reported ecological and biochemical diversity of the lignin microbial niches, and discuss the findings.
  •  
36.
  • Cabero, Karen, et al. (författare)
  • A cellulolytic Hypocrea strain isolated from South American brave straw produces a modular xylanase.
  • 2012
  • Ingår i: Carbohydrate Research. - : Elsevier BV. - 1873-426X .- 0008-6215. ; 356, s. 215-223
  • Tidskriftsartikel (refereegranskat)abstract
    • Cellulase-producing fungi from the Andean regions in Bolivia, an ecosystem characterized as an extreme arid highland, were studied. Thirty-two isolates were screened for presence of cellulase activity using carboxymethyl cellulose (CMC) as carbon source, and activity was confirmed using a filter paper assay. One isolate, denoted as BLT1C was selected from this screening, and sequence analysis of the internal transcribed spacer (ITS) classified the strain as Hypocrea lixii. The secretome of BLT1C showed high xylanase activity (compared to that of two reference Trichoderma reesei strains) when cultivated using brave straw, an abundant native grass from the area, as carbon source. SDS-PAGE analysis revealed three main protein-bands (18, 32 and 65kDa) and in-gel digestion and mass spectrometry combined with activity analysis showed that these proteins were active xylanases with molecular masses corresponding to (I) a single glycoside hydrolase family 11 catalytic module (18kDa), and (II, III) modular enzymes, with the GH11 catalytic domain connected to a module of unknown function (32kDa) or putatively connected to a GH7 catalytic module (65kDa). The N-terminal sequence of the 65kDa xylanase did not show significant sequence similarities to deposited sequences. The collected data on xylanase activity, molecular mass, GH11-sequence conservation, combined with lack of sequence similarities in the N-terminus show that the 65kDa band corresponds to a novel modular xylanase.
  •  
37.
  •  
38.
  • Campos, Joana, et al. (författare)
  • Fed-batch strategies for biodetoxification in production of optically pure lactic acid from softwood hydrolysate using Pediococcus acidilactici
  • 2023
  • Ingår i: Process Biochemistry. - : Elsevier BV. - 1359-5113. ; 125, s. 162-170
  • Tidskriftsartikel (refereegranskat)abstract
    • Optically pure lactic acid (LA) is important for the development of specialized applications for poly-lactic acid (PLA). To pursue sustainable production, feedstocks such as lignocellulosic biomass need to be investigated. The present study focused on the production of L-LA from softwood hydrolysate with Pediococcus acidilactici TY112. One of the challenges when using this substrate is the presence of inhibitors, such as furfural and 5-hydroxymethylfurfural (HMF), formed during pretreatment. To investigate adaptation, fed-batch experiments on softwood hydrolysate and model media were conducted. Although LA production was still affected by the presence of other inhibitors in the hydrolysate, P. acidilactici TY112 was capable of converting HMF and furfural and partly detoxify both hydrolysate and synthetic media. The strain adapted to the inhibitors present, if fed at a low rate (30 mL·h−1 for model medium with inhibitors and 15 mL·h−1 for softwood hydrolysate, both with 30 g·L−1 glucose and 45 g·L−1 mannose). Regarding carbon source consumption, a feeding rate of 30 mL·h−1 limited the uptake of glucose, leading to improved mannose uptake, with LA yields higher than 0.86 g·g−1. This study shows the potential of P. acidilactici TY112 for the production of L-LA from softwood hydrolysate which is regarded as inhibitory.
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39.
  • Campos, Joana, et al. (författare)
  • Optically pure lactic acid production from softwood-derived mannose by Pediococcus acidilactici
  • 2021
  • Ingår i: Journal of Biotechnology. - : Elsevier BV. - 0168-1656. ; 335, s. 1-8
  • Tidskriftsartikel (refereegranskat)abstract
    • Softwood is of interest as a renewable carbon source for production of lactic acid. Softwood hydrolysate contains a high content of mannose. Lactic acid production from mannose by two modified strains, L-lactic acid producing Pediococcus acidilactici TY112 and D-lactic acid producing ZP26, was investigated in the current work. The two strains efficiently converted mannose to L- and D-lactate isomers with an optical purity exceeding 99 %, although the mannose utilization rates were lower than the glucose utilization rates. The mannose conversion to L- and D-lactic acids by P. acidilactici was also confirmed in dilute spruce hemicellulose hydrolysate. The present study provides important knowledge on utilization of the spectrum of fermentable sugars in softwood for future production of chiral lactic acid from lignocellulose feedstocks.
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40.
  • Campos, Joana, et al. (författare)
  • Overcoming extended lag phase on optically pure lactic acid production from pretreated softwood solids
  • 2023
  • Ingår i: Frontiers in Bioengineering and Biotechnology. - 2296-4185. ; 11
  • Tidskriftsartikel (refereegranskat)abstract
    • Optically pure lactic acid (LA) is needed in PLA (poly-lactic acid) production to build a crystalline structure with a higher melting point of the biopolymer than that of the racemic mixture. Lignocellulosic biomass can be used as raw material for LA production, in a non-food biorefinery concept. In the present study, genetically engineered P. acidilactici ZP26 was cultivated in a simultaneous saccharification and fermentation (SSF) process using steam pretreated softwood solids as a carbon source to produce optically pure D-LA. Given the low concentrations of identifiable inhibitory compounds from sugar and lignin degradation, the fermentation rate was expected to follow the rate of enzymatic hydrolysis. However, added pretreated solids (7% on weight (w/w) of water-insoluble solids [WIS]) significantly and immediately affected the process performance, which resulted in a long lag phase (more than 40 h) before the onset of the exponential phase of the fermentation. This unexpected delay was also observed without the addition of enzymes in the SSF and in a model fermentation with glucose and pretreated solids without added enzymes. Experiments showed that it was possible to overcome the extended lag phase in the presence of pretreated softwood solids by allowing the microorganism to initiate its exponential phase in synthetic medium, and subsequently adding the softwood solids and enzymatic blend to proceed to an SSF with D-LA production.
  •  
41.
  • Carlquist, Magnus, et al. (författare)
  • Process engineering for bioflavour production with metabolically active yeast - a minireview.
  • 2015
  • Ingår i: Yeast. - 1097-0061. ; 32:1, s. 123-143
  • Forskningsöversikt (refereegranskat)abstract
    • Flavours are biologically active molecules of large commercial interest in the food, cosmetics, detergent and pharmaceutical industry. The production of flavours can take place by either extraction from plant materials, chemical synthesis, through biological conversion of precursor molecules or through de novo biosynthesis. The latter alternatives are gaining importance through the rapidly growing fields of systems biology and metabolic engineering giving efficient production hosts for the so-called "bioflavours", which are natural flavour and/or fragrance compounds obtained with cell factories or enzymatic systems. One potential production host for bioflavour is yeast. In this mini-review, we give an overview of bioflavour production in yeast from the process engineering perspective. Two specific examples - production of 2-phenylethanol and vanillin - are used to illustrate process challenges and strategies used.
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42.
  • Carlqvist, Karin, et al. (författare)
  • Life cycle assessment for identification of critical aspects in emerging technologies for the extraction of phenolic compounds from spruce bark
  • 2022
  • Ingår i: Journal of Cleaner Production. - : Elsevier BV. - 0959-6526. ; 333
  • Tidskriftsartikel (refereegranskat)abstract
    • Polyphenolic compounds in bark are resources of great interest to produce renewable chemicals and several different technologies are available or under early development for the extraction of these types of compounds. Since critical environmental effects of a product are often set during the design phase, it is important to use life cycle assessment (LCA) to identify the steps resulting in the largest environmental burdens and the overall performance of the various technologies at an early stage during technology development. In addition, for a better understanding of the environmental impact of the future system, it is needed to consider an up-scaled process already in early process development. In the current study, LCAs of three different technologies; hot water extraction (HWE), ultrasound assisted extraction (UAE), and supercritical fluid extraction (SFE) for the extraction of phenolic compounds from spruce bark were compared in a large-scale production scenario. The study includes industrially relevant heat sources and heating technologies, downstream separations, solvent recovery, and heat recovery within the processes. The LCA shows that the simpler HWE process has a lower environmental impact per amount of phenolic compound extracted than UAE and SFE unless the extraction yields of the latter are more than about 5 times that of HWE. The reason for this result is mainly the environmental burden caused by the consumption of ethanol in the UAE and SFE processes, which accounts for more than 70% of the total environmental burden in most impact categories. Even if bioethanol produced with a particularly low carbon footprint would be used, the impact from ethanol use in the extractions would be considerable. UAE and SFE were also more dependent on the use of electricity. In the base case scenario, electricity produced with a low share of fossil resources was used, and electricity was in this case not one of the main contributors to the environmental impact of the processes. However, if the production of electricity is largely fossil-based, it comes out as a significant factor. Furthermore, the heat recovery in an up-scaled process is very important and accounts for a reduction of 35–60% net heat demand. As a complement to LCAs, future studies of promising polyphenolic compound production systems should also include economic aspects and performance.
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43.
  • Carlqvist, Karin, et al. (författare)
  • Life-cycle assessment of the production of cationized tannins from Norway spruce bark as flocculants in wastewater treatment
  • 2020
  • Ingår i: Biofuels, Bioproducts and Biorefining. - : Wiley. - 1932-104X .- 1932-1031. ; 14:6, s. 1270-1285
  • Tidskriftsartikel (refereegranskat)abstract
    • It will be necessary to make efficient use of our resources if our society is to be converted into a bio-based economy. Every year large side streams of bark are produced in sawmills and pulp mills. In addition to utilizing the bark for heat and electricity production, as happens today, high-value chemical components could be extracted prior to energy conversion. These components include tannins. Cationized tannins have already been indicated as promising renewable flocculants in wastewater treatment. However, today's industrial production of tannins uses species from subtropical or temperate climates, and there has so far been little attention to the use of tannins from Norway spruce (Picea abies), an important species in forestry in the subarctic climate. The present life-cycle assessment (LCA) was undertaken to understand the environmental performance of the production of cationized tannins from the bark of Norway spruce and how the environmental impact is distributed along the production system. This work was connected to the Interreg Botnia-Atlantica TanWat research project, which studies the production and use of cationized tannins from Norway spruce for wastewater treatment at a pilot scale. The present LCA shows that the main environmental impact stems from the reagents used in the cationization step. The purification step could also be a significant issue depending on the possibility of reusing the eluent (ethanol) and the lifetime of the resin. The importance of running the processes with as concentrated streams as possible to minimize the need of process water and energy was also confirmed
  •  
44.
  • Carrasco, Cristhian, et al. (författare)
  • Arabinosylated phenolics obtained from SO2-steam-pretreated sugarcane bagasse
  • 2012
  • Ingår i: Journal of Chemical Technology and Biotechnology. - : Wiley. - 0268-2575. ; 87:12, s. 1723-1726
  • Tidskriftsartikel (refereegranskat)abstract
    • A pentose-rich hydrolysate fraction obtained by extraction of steam-pretreated sugarcane bagasse was analysed with regard to dissolved phenolics. The liquid obtained after steam pretreatment (2% SO2 (w/w) at 190 degrees C for 5 min) was divided into two parts: one containing dissolved compounds originating from hemicellulose (with xylose as the dominating compound), and the other containing predominantly dissolved compounds originating from lignin. Using nuclear magnetic resonance, the main dissolved compounds originating from lignin were identified as the glycosylated aromatics, 5-O-(trans-feruloyl)-L-Arabinofuranose and 5-O-(trans-coumaroyl)-L-Arabinofuranose, together with p-coumaric acid and small amounts of more common free phenolics such as p-hydroxybenzaldehyde, p-hydroxybenzoic acid and vanillin. The phenolic compounds were analysed and quantified using reversed-phase high-performance liquid chromatography. The findings show that SO2 steam explosion opened up new degradation pathways during lignin degradation. Copyright (c) 2012 Society of Chemical Industry
  •  
45.
  • Carrasco, Cristhian, et al. (författare)
  • SO2-catalysed steam pretreatment of quinoa stalks
  • 2015
  • Ingår i: Journal of Chemical Technology and Biotechnology. - : Wiley. - 0268-2575. ; 90:1, s. 64-71
  • Tidskriftsartikel (refereegranskat)abstract
    • BACKGROUNDQuinoa is a pseudo-cereal grown predominantly in South America. The quinoa stalks are lignocellulosic residues, which have a limited use today. The objective of the current study was to assess the potential of this material as a source of monosaccharides for fermentation purposes by means of steam pretreatment giving sugars from the hemicellulose part, and enzymatic hydrolysis of the solid fraction obtained. SO2 catalysed steam pretreatment was carried out with a holding time of 5min at temperatures between 180 and 220 degrees C. The pretreatment was carried out at two different scales, a small reactor of size 0.5L and a somewhat larger reactor of size 10L, to allow comparison of scale effects in the pretreatment. RESULTSThe highest xylose yield in the liquid phase, obtained after pretreatment at 210 degrees C, was 80%. In the smaller scale unit, longer residence times were needed. The enzymatic hydrolysis, at an enzyme loading of 15 FPU g(-1) glucan and a WIS loading of 2%, resulted in a glucose yield of 70% based on the original glucan. The overall sugar yield, including the xylan hydrolysed in the enzymatic treatment, at dilute conditions was 75%. CONCLUSIONSSO2 catalysed pretreatment of quinoa straw followed by enzymatic hydrolysis gave a relatively good sugar yield. However, the yield obtained was somewhat lower than previously reported for similar materials, such as wheat straw and sugarcane bagasse, steam pretreated with SO2. (c) 2013 Society of Chemical Industry
  •  
46.
  • Carrasco, Cristhian, et al. (författare)
  • SO2-catalyzed steam pretreatment and fermentation of enzymatically hydrolyzed sugarcane bagasse
  • 2010
  • Ingår i: Enzyme and Microbial Technology. - : Elsevier BV. - 0141-0229. ; 46:2, s. 64-73
  • Tidskriftsartikel (refereegranskat)abstract
    • Sugarcane bagasse is a lignocellulosic residue obtained from sugarcane milling, and a potentially interesting raw material that can be used for fuel ethanol production. In the present study, bagasse was steam pretreated at temperatures between 180 and 205 ◦C, with holding times of 5–10 min using SO2 as a catalyst to determine conditions that provide a good recovery of pentoses and a suitable material for enzymatic hydrolysis. Pretreatment conducted at 190 ◦C for 5 min gave a pentose yield of 57%, with only minor amounts of degradation compounds formed. Commercial cellulolytic enzymes were used to hydrolyze the obtained fiber fractions after pretreatment at different water-insoluble solid contents (2%, 5% and 8% WIS). The overall highest sugar yield achieved from bagasse was 87% at 2% WIS. Fermentation tests were made on both the pentose-rich hemicellulose hydrolysate obtained from the pretreatment, and the enzymatic hydrolysates obtained from the fiber fractions using the xylose-fermenting strain of Saccharomyces cerevisiae TMB3400, as well as the natural xylose-utilizing yeast Pichia stipitis CBS 6054. The pretreatment hydrolysates produced at 2% WIS as well as the enzymatic hydrolysates showed a complete glucose fermentability indicating a low toxicity to the yeasts. The best xylose conversion (more than 60%) was achieved by the strain TMB3400 at 2% WIS.
  •  
47.
  • Carrasco, Cristhian, et al. (författare)
  • Steam pretreatment and fermentation of the straw material "Paja Brava" using simultaneous saccharification and co-fermentation.
  • 2011
  • Ingår i: Journal of Bioscience and Bioengineering. - : Elsevier BV. - 1347-4421 .- 1389-1723. ; 111, s. 167-174
  • Tidskriftsartikel (refereegranskat)abstract
    • Pretreatment, enzymatic hydrolysis and simultaneous saccharification and fermentation (SSF) of the South American straw material Paja Brava were investigated. Suitable process conditions for an SO(2)-catalyzed steam pretreatment of the material were determined and assessed by enzymatic digestibility of obtained fiber slurries for 72h at a water insoluble solids (WIS) content of 2%. The best pretreatment conditions obtained (200°C, 5min holding time and 2.5% SO(2)) gave an overall glucose yield following enzymatic hydrolysis of more than 90%, and a xylose yield of about 70%. Simultaneous saccharification and co-fermentation of glucose and xylose (SSCF) of the pretreated material using the xylose-fermenting strain Saccharomyces cerevisiae TMB3400 was examined at WIS contents between 5% and 10%. In agreement with previous studies on other materials, the overall ethanol yield and also the xylose conversion decreased somewhat with increasing WIS content in the SSCF. In batch SSCF, the xylose conversion obtained was almost 100% at 5% WIS content, but decreased to 69% at 10% WIS. The highest ethanol concentration obtained for a WIS content of 10% was about 40g/L, corresponding to a yield of 0.41g/g in a fed-batch SSCF. The Paja Brava material has previously been found difficult to hydrolyze in a dilute-acid process. However, the SSCF results obtained here show that similar sugar yields and fermentation performance can be expected from Paja Brava as from materials such as wheat straw, corn stover or sugarcane bagasse.
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48.
  •  
49.
  • Cimander, Christian (författare)
  • Multivariate monitoring, modelling and control for stabilization of bioprocesses
  • 2002
  • Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • The obstacles to overcome low reproducibility and stability of bioprocesses are numerous. Underlying biochemical processes are inherently non-linear, complex and subject to shifting initial conditions. Problems with high variability are also associated to production strains and scale-up of a bioprocess to largescale bioreactors. Reliable on-line monitoring of key process variables is still a challenging task and hinders the closed-loop control of these key process variables. In this thesis, methods for stabilization of bioprocesses by means of multivariate on-line monitoring, modelling and control are studied.The foundation was laid with the development of integrated multivariate bioprocess monitoring, modelling and control within a real-time knowledge-based expert system. Thereby, a large number of signals from different advanced on-line analyzers ranging from mass spectroscopy via on-line HPLC to nearinfrared spectroscopy and electronic noses, could be used in combination with a variety of multivariate modelling and control tools for a flexible development of methods for stabilization of bioreactor processes. Subsequently, it could be shown how problems related to the initial conditions of a bioprocess can be solved by a multivariate assessment of the preculture quality. Furthermore, it was demonstrated how qualitative and quantitative key process variables can be made available and applied for process supervision; here, multivariate statistical process modelling and neural network sensor fusion from on-line monitoring of bioprocesses with advanced on-line analyzers were used. Finally, a closed-loop control method was presented, showing how feedback control of a multivariate key process variable trajectory can improve adherence to the specifications of the bioprocess. As model systems, aerobic fed-batch cultivations using recombinant Escherichia coli and anaerobic yoghurt batch fermentations have been used. The results provide general methods for multivariate stabilization of bioprocesses in precultivation steps, laboratory-scale and production-scale. They show that multivariate monitoring, modelling and control can provide a functional and versatile framework for reduced batch-tobatch variation and stabilization of bioprocesses with possible implications on product quality and process economics.
  •  
50.
  • Costa, Thales H.F., et al. (författare)
  • Demonstration-scale enzymatic saccharification of sulfite-pulped spruce with addition of hydrogen peroxide for LPMO activation
  • 2020
  • Ingår i: Biofuels, Bioproducts and Biorefining. - : Wiley. - 1932-104X .- 1932-1031. ; 14:4, s. 734-745
  • Tidskriftsartikel (refereegranskat)abstract
    • The saccharification of lignocellulosic materials like Norway spruce is challenging due to the recalcitrant nature of the biomass, and it requires optimized and efficient pretreatment and enzymatic hydrolysis processes to make it industrially feasible. In this study, we report successful enzymatic saccharification of sulfite-pulped spruce (Borregaard's BALI™ process) at demonstration scale, achieved through the controlled delivery of hydrogen peroxide (H2O2) for the activation of lytic polysaccharide monooxygenases (LPMOs) present in the cellulolytic enzyme preparation. We achieved 85% saccharification yield in 4 days using industrially relevant conditions – that is, an enzyme dose of 4% (w/w dry matter of substrate) of the commercial cellulase cocktail Cellic CTec3 and a substrate loading of 12% (w/w). Addition of H2O2 and the resulting controlled and high LPMO activity had a positive effect on the rate of saccharification and the final sugar titer. Clearly, the high LPMO activity was dependent on feeding the reactors with the LPMO co-substrate H2O2, as in situ generation of H2O2 from molecular oxygen was limited. These demonstration-scale experiments provide a solid basis for the use of H2O2 to improve enzymatic saccharification of lignocellulosic biomass at large industrial scale.
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