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1.
  • Sardari, Roya, et al. (författare)
  • Evaluation of sequential processing for the extraction of lipids, starch and proteins from wheat bran
  • 2019
  • Ingår i: Frontiers in Bioengineering and Biotechnology. - : Frontiers Media SA. - 2296-4185. ; 7:413
  • Tidskriftsartikel (refereegranskat)abstract
    • In line with the need to better utilize agricultural resources, and valorize underutilized fractions, we have developed protocols to increase the use of wheat bran, to improve utilization of this resource to additional products. Here, we report sequential processing for extraction of starch, lipids, and proteins from wheat brans with two different particle sizes leaving a rest-material enriched in dietary fiber. Mild water-based extraction of starch resulted in maximum 81.7 ± 0.67% yield. Supercritical fluid extraction of lipids by CO2 resulted in 55.2 ± 2.4% yield. This was lower than the corresponding yield using Soxhlet extraction, which was used as a reference method, but allowed a continued extraction sequence without denaturation of the proteins remaining in the raw-material. Alkaline extraction of non-degraded proteins resulted in a yield corresponding to one third of the total protein in the material, which was improved to reach 62 ± 8% by a combination of wheat bran enzymes activation followed by Osborne fractionation. The remaining proteins were extracted in degraded form, resulting in maximum 91.6 ± 1.6% yield of the total proteins content. The remaining material in both fine and coarse bran had a fiber content that on average corresponded to 73 ± 3%. The current work allows separation of several compounds, which is enabling valorization of the bran raw-material into several products.
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2.
  • Al-Rudainy, Basel, et al. (författare)
  • Antisolvent precipitation of hemicelluloses, lignosulfonates and their complexes from ultrafiltrated spent sulfite liquor (SSL)
  • 2018
  • Ingår i: Holzforschung. - : Walter de Gruyter GmbH. - 1437-434X .- 0018-3830. ; 72:10, s. 839-850
  • Tidskriftsartikel (refereegranskat)abstract
    • The possibility of precipitating high molecular weight (MW) softwood hemicelluloses has been investigated. Solids were precipitated from a sodium-based spent sulfite liquor with the anti-solvents acetone, ethanol and methanol and the effects of solute concentration, pH and temperature on the precipitation were studied. The product yield, degree of separation, MW and structure of the different fractions were determined using gravimetric analysis, high performance liquid chromatography (HPLC), ultraviolet–visible (UV-Vis) spectroscopy, size exclusion chromatography (SEC), and two-dimensional nuclear magnetic resonance (2D NMR). A direct correlation was found between the dielectric constant (also called relative permittivity) of the bulk solution and the yield of precipitants, based on which the separation of the solutes was predictable. The highest yield and degree of separation observed was an intercept around 76% with 47.5% acetone, which was the most efficient anti-solvent.
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3.
  • Al-Rudainy, Basel, et al. (författare)
  • From lab-scale to on-site pilot trials for the recovery of hemicellulose by ultrafiltration: Experimental and theoretical evaluations
  • 2020
  • Ingår i: Separation and Purification Technology. - : Elsevier BV. - 1873-3794 .- 1383-5866. ; 250
  • Tidskriftsartikel (refereegranskat)abstract
    • Spent sulfite liquor (SSL) is a byproduct of the sulfite pulping process of wood. SSL usually contains monosugars and lignosulfonates, which are fermented to produce ethanol and dried to generate lignosulfonate salts. However, the SSL that was used in this work was derived from the first step of a 2-step sulfite pulping process of softwood under mild pulping conditions in the first stage of cooking. The resulting SSL contained polymeric hemicelluloses, which are not used today but have many potential applications. The up-concentration of this SSL had been performed on a lab scale by ultrafiltration. However, the pilot-scale ultrafiltration of hemicellulose-rich sodium-based SSL has not been reported. In this study, the operating conditions for the lab-scale concentration of hemicellulose-rich, sodium-based SSL were examined in a pilot-scale membrane filtration unit. The permeate flux and retention of products were lower in the pilot equipment compared with the lab-scale setup, perhaps related to the lower Reynolds number and shear rate in the former, as indicated by simulations of computational fluid dynamics. The pilot equipment also ran at a higher volume reduction compared with the lab-scale system, which could explain the difference in flux and retention. The effects of fouling and cleaning were also determined, wherein an alkaline cleaning step (pH 11) for 1 h was sufficient to remove foulants and maintain a stable average flux of 88 L/m2h and the nonchanging retention of products.
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4.
  • Al-Rudainy, Basel, et al. (författare)
  • From waste to high-value products: Impact of galactoglucomannan purity on selected hydrogel properties
  • 2018
  • Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
    • Hydrogels are a hydrophilic network of polymers (usually cross-linked polysaccharides) that are natural or synthetic. Applications of hydrogels are many in the biomedical field. Because of the high water absorption (10 to 200 grams of water per gram of hydrogel), hydrogels have a high degree of flexibility similar to natural human tissue. Human cells can be incorporated into the hydrogel, which in turn can be used to repair damaged tissue. An option is to incorporate drugs in the gels to treat a damaged area by a sustained-release drug-delivery system. Other uses have been in the production of bio-sensors, as absorbent in, e.g. diapers or in the production of contact lenses.Hemicelluloses (in this work galactoglucomannan (GGM)) are a promising renewable raw material for the production of hydrogels. Given their high abundance (constituting up to 25% of the wood cell walls) and current lack of use (usually incinerated together with other biopolymers in the pulp and paper industry), makes this work valuable from an economical and industrial point-of-view.In this work, we examine the possibility to produce hydrogels from GGM extracted from sodium-based spent-sulfite-liquor using a combination of membrane filtration and anti-solvent precipitation. The impact of GGM purity or the addition of lignosulfonates to the cross-linking reaction mixture (in-direct effect of the downstream processing, which affect the overall process economy) on the mechanical, thermal and chemical properties of the hydrogel have been examined and evaluated.
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5.
  • Al-Rudainy, Basel, et al. (författare)
  • Galactoglucomannan Recovery with Hydrophilic and Hydrophobic Membranes: Process Performance and Cost Estimations
  • 2019
  • Ingår i: Membranes. - : MDPI AG. - 2077-0375. ; 9:8
  • Tidskriftsartikel (refereegranskat)abstract
    • In this study, we compared the GR51PP (hydrophobic/polysulfone) membrane with a series of hydrophilic (regenerated cellulose) membranes with the aim of increasing the retention of products and decreasing membrane fouling. The raw material used was a sodium-based spent sulfite liquor from the sulfite pulping process of spruce and pine. The results show that the hydrophilic membranes were superior to the hydrophobic membranes in terms of higher fluxes (up to twice the magnitude), higher product retentions and less fouling (up to five times lower fouling). The fouling was probably caused by pore blocking as observed in earlier studies. However, the hydrophilic membranes had a lower affinity for lignin, which was indicated by the lower retention and fouling. This also resulted in a separation degree, which was higher compared with the hydrophobic membrane, thus yielding a higher galactoglucomannan (GGM) purity. 2D HSQC NMR results show that no major structural differences were present in the hydrophilic and hydrophobic retentates. A techno-economical evaluation resulted in the RC70PP being chosen as the most cost-efficient membrane in terms of flux and product recovery.
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6.
  • Al-Rudainy, Basel, et al. (författare)
  • Hemicellulose Recovery from Spent-Sulfite-Liquor: Lignin Removal by Adsorption to Resins for Improvement of the Ultrafiltration Process
  • 2020
  • Ingår i: Molecules. - : MDPI AG. - 1420-3049. ; 25:15
  • Tidskriftsartikel (refereegranskat)abstract
    • In this work, three polymeric resins were examined as alternatives for the separation of hemicellulose and lignin. The aim was to remove the lignin from spent-sulfite-liquor (SSL) prior to ultrafiltration, producing a hemicellulose-rich retentate with high purity, and increase the capacity of the membrane filtration. The lignin in the SSL was sulfonated; thus, two of the resins were anion exchangers and 1 was hydrophobic. The data from the equilibrium studies and adsorption kinetics were fitted to established models, and the results were interpreted based on these observations. The strongly basic anion exchanger performed best with regard to lignin removal. The adsorption followed the Sips isotherm, indicating that the process was cooperative with chemisorption as the main reaction between the adsorbate and adsorbent based on the kinetics. Regeneration of the adsorbent was also possible, wherein 100 g/L NaCl was sufficient to recover 98% of the lignin. The lignin removal had a positive effect on the ultrafiltration process, in which the flux increased by 38% and the extent of separation between the hemicellulose and lignin rose from 17% to 59%.
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7.
  • Al-Rudainy, Basel, et al. (författare)
  • Impact of lignin content on the properties of hemicellulose hydrogels
  • 2019
  • Ingår i: Polymers. - : MDPI AG. - 2073-4360. ; 11:1
  • Tidskriftsartikel (refereegranskat)abstract
    • Hemicellulose is a promising renewable raw material for the production of hydrogels. This polysaccharide exists in large amounts in various waste streams, in which they are usually impure and heavily diluted. Several downstream processing methods can be combined to concentrate and purify the hemicellulose. However, such an approach can be costly; hence, the effect of impurities on the formation and properties of hydrogels must be determined. Lignin usually exists in these waste streams as a major impurity that is also difficult to separate. This compound can darken hydrogels and decrease their swellability and reactivity, as shown in many studies. Other properties and effects of lignin impurities are equally important for the end application of hydrogels and the overall process economy. In this work, we examined the feasibility of producing hydrogels from hemicelluloses that originated from sodium-based spent sulfite liquor. A combination of membrane filtration and anti-solvent precipitation was used to extract and purify various components. The influence of the purity of hemicellulose and the addition of lignosulfonates (emulated impurities in the downstream processing) to the crosslinking reaction mixture on the mechanical, thermal, and chemical properties of hydrogels was determined.
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8.
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9.
  • Al-Rudainy, Basel, et al. (författare)
  • Influence of prefiltration on membrane performance during isolation of lignin-carbohydrate complexes from spent sulfite liquor
  • 2017
  • Ingår i: Separation and Purification Technology. - : Elsevier BV. - 1383-5866. ; 187, s. 380-388
  • Tidskriftsartikel (refereegranskat)abstract
    • In this study, we examined the isolation of lignin-carbohydrate complexes (LCCs) from sodium-based spent sulfite liquor, in conjunction with minimization of membrane fouling. We screened 3 polysulfone (PS) membranes with cutoffs of 100, 50, and 25 kDa, respectively. Flux and retention for the 100- and 50-kDa membranes had the same order of magnitude, indicating that these properties were determined by fouling that formed on the membrane—not pore size. The PS membrane with the 50-kDa cutoff performed best in terms of flux and retention of lignin-carbohydrate complexes and experienced the least membrane fouling. Two prefiltration methods were used to decrease the fouling of the 50-kDa membrane: a 0.2-μm PS microfiltration membrane and dead-end filtration with 10-um filter cloth and a 4 wt% mixture of kieselguhr (diatomite) and spent sulfite liquor prior to filtration. Prefiltration of the SSL with microfiltration increased the flux 3-fold and decreased the fouling grade from 49% to 7.2%. Dead-end filtration effected a 16% increase in flux and a fouling grade of 17%. The retention of LCC during microfiltration was high, which resulted in a loss of high-molecular-weight products, whereas the loss of LCC during dead-end filtration was negligible. A 50-kDa PS membrane performed best with regard to the recovery of lignin-carbohydrate complexes from spent sulfite liquor. Also, dead-end filtration is a promising method for eliminating membrane fouling.
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10.
  • Al-Rudainy, Basel, et al. (författare)
  • Techno-economic evaluation for the process optimization of galactoglucomannan and lignin recovery by ultrafiltration
  • 2018
  • Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
    • Galactoglucomannans (GGM) can be used as a precursor for the production of surfactants, plastics, hydrogels etc. However, separation of galactoglucomannan (GGM) from lignin and lignin-carbohydrate-complexes using membrane filtration is difficult. Precipitation of GGM with anti-solvents is an approach that has been previously studied. A membrane filtration step prior to precipitation is economically beneficial to decrease anti-solvent requirements with increasing concentration of GGM. However, previous studies have shown that membrane fouling is a problem that can have a large impact on the life-time of the membranes but also the overall yield of the products.The raw material used in this study was a sodium-based spent-sulfite-liquor (SSL) provided by Domsjö Fabriker (Örnsköldsvik, Sweden) and is the outtake after the first pulping step of softwood (60 % Picea abies and 40 % Pinus sylvestris). The SSL was concentrated with a 50 kDa polysulfone membrane (hydrophobic) and four regenerative cellulose membranes (30, 20, 10 and 5 kDa) (hydrophilic) to a volume reduction of 90 %. The resulting retentate was analyzed for the composition and the product yields were calculated. Membrane data, such as, flux, trans-membrane pressure, cross-flow velocity and degree of fouling were used together with the GGM yields in a techno-economic evaluation to find a cost-efficient process for the separation and purification of GGM and lignin from SSL.
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11.
  • Alkasrawi, Malek, et al. (författare)
  • Recirculation of process streams in fuel ethanol production from softwood based on simultaneous saccharification and fermentation
  • 2002
  • Ingår i: Applied Biochemistry and Biotechnology. - 0273-2289 .- 1559-0291. ; 98, s. 849-861
  • Konferensbidrag (refereegranskat)abstract
    • The effect of process stream recirculation on ethanol production from steam- pretreated softwood based on simultaneous saccharification and fermentation (SSF) was investigated for two process configurations. In the first configuration, a part of the stillage stream after distillation was recycled and, in the second configuration, the liquid after SSF was recycled. The aim was to minimize the energy consumption in the distillation of the fermentation broth and in the evaporation of the stillage, as well as the use of fresh water. However, recirculation leads to an increased concentration of nonvolatiles in the first configuration, and of both volatiles and nonvolatiles in the second configuration. These substances might be inhibitory to the enzymes and the yeast in SSF. When 60% of the fresh water was replaced by stillage, the ethanol yield and the productivity were the same as for the configuration without recirculation. The ethanol production cost was reduced by 17%. In the second configuration, up to 40% of the fresh water could be replaced without affecting the final ethanol yield, although the initial ethanol productivity decreased. The ethanol production cost was reduced by 12%. At higher degrees of recirculation,fermentation was clearly inhibited, resulting in a decrease in ethanol yield while hydrolysis seemed unaffected.
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12.
  • Alkasrawi, Malek, et al. (författare)
  • The effect of Tween-20 on simultaneous saccharification and fermentation of softwood to ethanol
  • 2003
  • Ingår i: Enzyme and Microbial Technology. - 0141-0229. ; 33:1, s. 71-78
  • Tidskriftsartikel (refereegranskat)abstract
    • Simultaneous sacchatification and fermentation (SSF) of steam-pretreated wood constitutes an attractive process configuration for ethanol production from biomass. However, the high enzyme addition in SSF contributes to a high process cost. In this study we explore the effect of the non-ionic surfactant Tween-20 as an additive in SSE Tween-20 addition at 2.5 g/l had several positive effects on SSF: (i) the ethanol yield was increased by 8%; (ii) the amount of enzyme loading could be reduced by 50%, while maintaining a constant yield; (iii) the enzyme activity increased in the liquid fraction at the end of SSF, probably by preventing unproductive binding of the cellulases to lignin, which could facilitate enzyme recovery; (iv) the time required to attain maximum ethanol concentration was reduced. Surfactants as an additive in SSF can significantly lower the operational cost of the process. However, less expensive surfactants must be investigated. (C) 2003 Elsevier Science Inc. All rights reserved.
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13.
  • Baudel, Henrique, et al. (författare)
  • Ethanol production from steam pretreated sugarcane bagasse via simultaneous saccharification and fermentation (SSF) using cellulase and b.glucosidase enzymes
  • 2008
  • Ingår i: XVII Congreso Brasileiro de Engenharia Quimica. ; , s. 1-8
  • Konferensbidrag (refereegranskat)abstract
    • Cellulosic ethanol was produced via simultaneous enzymatic hydrolysis and fermentation of steam pretreated sugarcane bagasse. Sugarcane bagasse underwent steam pretreatments at Log Ro 3.05-4.09, under catalysed (SO2 2% and H2SO4 0.25%) and uncatalysed conditions. Digestibilities of the steam pretreated bagasse were assessed via enzymatic hydrolysis using cellulase (Celluclast 1.5L) and B-glucosidase (Novozym 188) enzyme formulations at 2% WIS, 40 ºC, pH 4.8, 72h under continuous stirring (200 rpm). SO2-catalysed steam pretreated bagasses produced at moderate severities (180 or 190 ºC, 5 minutes) presented digestibilities up to 82%. Hemicellulose removal influenced pretreatment efficiency rather than delignification. SO2-steam pretreated bagasses were processed by SSF (simultaneous saccharification and fermentation) at 5% WIS loading. Yields of 0.40-0.41 g ethanol/g glucose (approx. 80% of the theoretical) and high selectivity through ethyl alcohol were obtained for all investigated conditions, leading to a potential production of 230 L ethanol/ ton dry bagasse.
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14.
  • Bondesson, Pia-Maria, et al. (författare)
  • Comparison of energy potentials from combined ethanol and methane production using steam-pretreated corn stover impregnated with acetic acid
  • 2014
  • Ingår i: Biomass & Bioenergy. - : Elsevier BV. - 1873-2909 .- 0961-9534. ; 67, s. 413-424
  • Tidskriftsartikel (refereegranskat)abstract
    • Acetic acid was investigated as a catalyst in steam pretreatment of corn stover. The purpose was to study ethanol production using either baker's yeast or a genetically modified pentose-fermenting version of Saccharomyces cerevisiae, KE6-12. Biogas production was investigated as an alternative for utilization of xylose. The high levels of acetic acid was found to be toxic using KE6-12. Some pentose fermentation was achieved, but the ethanol end concentration was almost the same as using baker's yeast (28 g L1 compared to 27 g L1). Using xylose for biogas production resulted in a high total energy recovery. The highest total energy recovery in the products, i.e. ethanol, methane and solids, obtained was 88% compared with the energy in ingoing raw material. This result was achieved when the solids and the liquid was separated after pretreatment.
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15.
  • Bondesson, Pia-Maria, et al. (författare)
  • Ethanol and biogas production after steam pretreatment of corn stover with or without the addition of sulphuric acid
  • 2013
  • Ingår i: Biotechnology for Biofuels. - : Springer Science and Business Media LLC. - 1754-6834. ; 6
  • Tidskriftsartikel (refereegranskat)abstract
    • Background: Lignocellulosic biomass, such as corn stover, is a potential raw material for ethanol production. One step in the process of producing ethanol from lignocellulose is enzymatic hydrolysis, which produces fermentable sugars from carbohydrates present in the corn stover in the form of cellulose and hemicellulose. A pretreatment step is crucial to achieve efficient conversion of lignocellulosic biomass to soluble sugars, and later ethanol. This study has investigated steam pretreatment of corn stover, with and without sulphuric acid as catalyst, and examined the effect of residence time (5-10 min) and temperature (190-210 degrees C) on glucose and xylose recovery. The pretreatment conditions with and without dilute acid that gave the highest glucose yield were then used in subsequent experiments. Materials pretreated at the optimal conditions were subjected to simultaneous saccharification and fermentation (SSF) to produce ethanol, and remaining organic compounds were used to produce biogas by anaerobic digestion (AD). Results: The highest glucose yield achieved was 86%, obtained after pretreatment at 210 degrees C for 10 minutes in the absence of catalyst, followed by enzymatic hydrolysis. The highest yield using sulphuric acid, 78%, was achieved using pretreatment at 200 degrees C for 10 minutes. These two pretreatment conditions were investigated using two different process configurations. The highest ethanol and methane yields were obtained from the material pretreated in the presence of sulphuric acid. The slurry in this case was split into a solid fraction and a liquid fraction, where the solid fraction was used to produce ethanol and the liquid fraction to produce biogas. The total energy recovery in this case was 86% of the enthalpy of combustion energy in corn stover. Conclusions: The highest yield, comprising ethanol, methane and solids, was achieved using pretreatment in the presence of sulphuric acid followed by a process configuration in which the slurry from the pretreatment was divided into a solid fraction and a liquid fraction. The solid fraction was subjected to SSF, while the liquid fraction, together with the filtered residual from SSF, was used in AD. Using sulphuric acid in AD did not inhibit the reaction, which may be due to the low concentration of sulphuric acid used. In contrast, a pretreatment step without sulphuric acid resulted not only in higher concentrations of inhibitors, which affected the ethanol yield, but also in lower methane production.
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16.
  • Bondesson, Pia-Maria, et al. (författare)
  • Optimizing Ethanol and Methane Production from Steam-pretreated, Phosphoric Acid-impregnated Corn Stover.
  • 2015
  • Ingår i: Applied Biochemistry and Biotechnology. - : Springer Science and Business Media LLC. - 1559-0291 .- 0273-2289. ; 175:3, s. 1371-1388
  • Tidskriftsartikel (refereegranskat)abstract
    • Pretreatment is of vital importance in the production of ethanol and methane from agricultural residues. In this study, the effects of steam pretreatment with phosphoric acid on enzymatic hydrolysis (EH), simultaneous saccharification and fermentation (SSF), anaerobic digestion (AD) and the total energy output at three different temperatures were investigated. The effect of separating the solids for SSF and the liquid for AD was also studied and compared with using the whole slurry first in SSF and then in AD. Furthermore, the phosphoric acid was compared to previous studies using sulphuric acid or no catalyst. Using phosphoric acid resulted in higher yields than when no catalyst was used. However, compared with sulphuric acid, an improved yield was only seen with phosphoric acid in the case of EH. The higher pretreatment temperatures (200 and 210 °C) resulted in the highest yields after EH and SSF, while the highest methane yield was obtained with the lower pretreatment temperature (190 °C). The highest yield in terms of total energy recovery (78 %) was obtained after pretreatment at 190 °C, but a pretreatment temperature of 200 °C is, however, the best alternative since fewer steps are required (whole slurry in SSF and then in AD) and high product yields were obtained (76 %).
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17.
  • Bondesson, Pia-Maria, et al. (författare)
  • Process design of SSCF for ethanol production from steam-pretreated, acetic-acid-impregnated wheat straw
  • 2016
  • Ingår i: Biotechnology for Biofuels. - : Springer Science and Business Media LLC. - 1754-6834. ; 9:1
  • Tidskriftsartikel (refereegranskat)abstract
    • BackgroundPretreatment is an important step in the production of ethanol from lignocellulosic material. Using acetic acid together with steam pretreatment allows the positive effects of an acid catalyst to be retained, while avoiding the negative environmental effects associated with sulphuric acid. Acetic acid is also formed during the pretreatment and hydrolysis of hemicellulose, and is a known inhibitor that may impair fermentation at high concentrations. The purpose of this study was to improve ethanol production from glucose and xylose in steam-pretreated, acetic-acid-impregnated wheat straw by process design of simultaneous saccharification and co-fermentation (SSCF), using a genetically modified pentose fermenting yeast strain Saccharomyces cerevisiae.ResultsEthanol was produced from glucose and xylose using both the liquid fraction and the whole slurry from pretreated materials. The highest ethanol concentration achieved was 37.5 g/L, corresponding to an overall ethanol yield of 0.32 g/g based on the glucose and xylose available in the pretreated material. To obtain this concentration, a slurry with a water-insoluble solids (WIS) content of 11.7 % was used, using a fed-batch SSCF strategy. A higher overall ethanol yield (0.36 g/g) was obtained at 10 % WIS.ConclusionsEthanol production from steam-pretreated, acetic-acid-impregnated wheat straw through SSCF with a pentose fermenting S. cerevisiae strain was successfully demonstrated. However, the ethanol concentration was too low and the residence time too long to be suitable for large-scale applications. It is hoped that further process design focusing on the enzymatic conversion of cellulose to glucose will allow the combination of acetic acid pretreatment and co-fermentation of glucose and xylose.
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18.
  • Bulkan, Gülru (författare)
  • Fungi-Based Biorefinery : Valorization of industrial residuals and techno-economic evaluation
  • 2022
  • Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • Sustainable development of society and industry is necessary for a safer future that is being challenged by environmental pollution, climate change, and scarcity of food and nutrition. Materials considered as waste can be converted into value-added products and energy, hence regained to the economy. Filamentous fungi are saprophytic microorganisms that show great potential for bioconversion of organic waste materials into a wide range of products, including ethanol, enzymes, fungal biomass, and organic acids. In this study, industrial residuals from bioethanol plants (thin stillage), agro-industrial residuals (oat husks), and fruit-processing residuals were considered as potential substrates for filamentous fungi. Different filamentous fungi species were investigated due to their edibility and ability to produce ethanol. The aim of this study was to investigate 1) the feasibility of a biorefinery concept and contribution of fungal products to the process economy, 2) the valorization of oat husks in the fungal biorefinery and its contribution to the process economy, and 3) the effect of bioactive compounds existing in fruit residuals on filamentous fungi in a synthetic medium.Bioconversion of thin stillage into value-added products, e.g., additional ethanol produced by filamentous fungi and edible fungal biomass for various feed/food markets, improved the process economy of a conventional bioethanol plant. Techno-economic analysis was carried out with Aspen Plus® and Aspen Process Economic Analyzer®. The economy of the conventional bioethanol plant was improved to 76% and 5.6-fold higher net present value when the fungal product was sold as fish feed and human food, respectively. When the fungal product was sold as human food, Aspergillus oryzae was more advantageous than Neurospora intermedia. It is possible to integrate lignocellulosic material into the fungi-based biorefinery and produce additional products, e.g., lignin and fungal biomass as feed/food products. Several scenarios for integrating organosolv pretreatment into the biorefinery were investigated. When protein-rich biomass was sold as feed and food, 71% and 7.9-fold higher net present value was obtained, respectively, compared to the conventional ethanol plant. Similarly, other materials, e.g., fruit residuals, can be valorized through the fungal biorefinery. However, bioactive compounds in fruit residuals have antimicrobial effects; therefore, it is essential to assess the sensitivity of fungi toward them for efficient processes. In addition to the fungi species utilized in thin stillage and oat husk valorization, two other industrially important fungi, Rhizopus oligosporus and A. niger, were tested against 10 bioactive compounds with antimicrobial properties (octanol, ellagic acid, (-)-epicatechin, quercetin, betanin, ascorbic acid, limonene, hexanal, car-3-ene, and myrcene). The bioactive compounds were added to a synthetic medium to reach final concentrations of 2.4, 24 and 240 mg/L, within their natural concentration in fruit/fruit residuals. A. oryzae, A. niger and N. intermedia were inhibited by octanol, while the latter fungus was also inhibited by D-Limonene at 240 mg/L. On the other hand, R. oligosporus was resistant to inhibitory compounds and increased the biomass yield. The highest change in biomass yield was in the presence of ellagic acid with up to a 4-fold increase. Ethanol and lactic acid yields were increased 38% and 30% in the presence of ellagic acid and betanin, respectively. Similarly, the existence of quercetin and ellagic acid, ascorbic acid, and hexanal increased the biomass yield of A. niger up to 28%.These studies can contribute to developing efficient and feasible biorefineries, in which filamentous fungi convert the industrial residuals into value-added products.
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19.
  • Bösch, Peter, et al. (författare)
  • Impact of dual temperature profile in dilute acid hydrolysis of spruce for ethanol production.
  • 2010
  • Ingår i: Biotechnology for Biofuels. - : Springer Science and Business Media LLC. - 1754-6834. ; 3
  • Tidskriftsartikel (refereegranskat)abstract
    • ABSTRACT: BACKGROUND: The two-step dilute acid hydrolysis (DAH) of softwood is costly in energy demands and capital costs. However, it has the advantage that hydrolysis and subsequent removal of hemicellulose-derived sugars can be carried out under conditions of low severity, resulting in a reduction in the level of sugar degradation products during the more severe subsequent steps of cellulose hydrolysis. In this paper, we discuss a single-step DAH method that incorporates a temperature profile at two levels. This profile should simulate the two-step process while removing its major disadvantage, that is, the washing step between the runs, which leads to increased energy demand. RESULTS: The experiments were conducted in a reactor with a controlled temperature profile. The total dry matter content of the hydrolysate was up to 21.1% w/w, corresponding to a content of 15.5% w/w of water insoluble solids. The highest measured glucose yield, (18.3 g glucose per 100 g dry raw material), was obtained after DAH cycles of 3 min at 209 degrees C and 6 min at 211 degrees C with 1% H2SO4, which resulted in a total of 26.3 g solubilized C6 sugars per 100 g dry raw material. To estimate the remaining sugar potential, enzymatic hydrolysis (EH) of the solid fraction was also performed. EH of the solid residue increased the total level of solubilized C6 sugars to a maximum of 35.5 g per 100 g dry raw material when DAH was performed as described above (3 min at 210 degrees C and 2 min at 211 degrees C with 1% H2SO4). CONCLUSION: The dual-temperature DAH method did not yield decisively better results than the single-temperature, one-step DAH. When we compared the results with those of earlier studies, the hydrolysis performance was better than with the one-step DAH but not as well as that of the two-step, single-temperature DAH. Additional enzymatic hydrolysis resulted in lower levels of solubilized sugars compared with other studies on one-step DAH and two-step DAH followed by enzymatic hydrolysis. A two-step steam pretreatment with EH gave rise to a considerably higher sugar yield in this study.
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20.
  • Capecchi, Lorenzo, et al. (författare)
  • Combined ethanol and methane production from switchgrass (Panicum virgatum L.) impregnated with lime prior to steam explosion
  • 2016
  • Ingår i: Biomass & Bioenergy. - : Elsevier BV. - 0961-9534. ; 90, s. 22-31
  • Tidskriftsartikel (refereegranskat)abstract
    • Pretreatments are crucial to achieve efficient conversion of lignocellulosic biomass to soluble sugars. In this light, switchgrass was subjected to 13 pretreatments including steam explosion alone (195 °C for 5, 10 and 15 min) and after impregnation with the following catalysts: Ca(OH)2 at low (0.4%) and high (0.7%) concentration; Ca(OH)2 at high concentration and higher temperature (205 °C for 5, 10 and 15 min); H2SO4 (0.2% at 195 °C for 10 min) as reference acid catalyst before steam explosion. Enzymatic hydrolysis was carried out to assess pretreatment efficiency in both solid and liquid fraction. Thereafter, in selected pretreatments the solid fraction was subjected to simultaneous saccharification and fermentation (SSF), while the liquid fraction underwent anaerobic digestion (AD). Lignin removal was lowest (12%) and highest (35%) with steam alone and 0.7% lime, respectively. In general, higher cellulose degradation and lower hemicellulose hydrolysis were observed in this study compared to others, depending on lower biomass hydration during steam explosion. Mild lime addition (0.4% at 195 °C) enhanced ethanol in SSF (+28% than steam alone), while H2SO4 boosted methane in AD (+110%). However, methane represented a lesser component in combined energy yield (ethanol, methane and energy content of residual solid). Mild lime addition was also shown less aggressive and secured more residual solid after SSF, resulting in higher energy yield per unit raw biomass. Decreased water consumption, avoidance of toxic compounds in downstream effluents, and post process recovery of Ca(OH)2 as CaCO3 represent further advantages of pretreatments involving mild lime addition before steam explosion.
  •  
21.
  • Capecchi, Lorenzo, et al. (författare)
  • Combined ethanol and methane production using steam pretreated sugarcane bagasse
  • 2015
  • Ingår i: Industrial Crops and Products. - : Elsevier BV. - 0926-6690. ; 74, s. 255-262
  • Tidskriftsartikel (refereegranskat)abstract
    • Efficient energy production relies on complementary use of crop residues, to enhance the amount of energy obtained per unit biomass. In this frame, sugarcane bagasse (SB) was pretreated and the resulting slurry and liquid fraction served, respectively, for simultaneous saccharification and fermentation (SSF) at high solid concentration (15%), and anaerobic digestion (AD). More specifically, SB was subjected to twelve pretreatments to enhance fiber deconstruction and subsequent energy output: steam explosion alone (195 degrees C for 5,10 and 15 min), after impregnation with 0.4% and 0.7% Ca(OH)(2), and at 205 degrees C for the same three times after 0.7% Ca(OH)(2) addition. After pretreatment, enzymatic hydrolysis was carried out on washed solid fraction; glucose and xylose were determined on this fraction as well as residual liquid fraction. On this latter, inhibitors (acetic and formic acid, furfural and 5-hydroxymethylfurfural) were also determined. Based on high glucose yield in enzymatic hydrolysis, three pretreatments were selected for SSF of the slurry. The same pretreatments underwent AD of the liquid fraction. Inhibitors augmented at increasing time and temperature, although never achieved critical levels. Lignin removal (range, 17-38%) was enhanced by lime addition, whereas increasing temperature and time did not contribute to delignification. Glucose yield in washed solid fraction varied accordingly. SSF exhibited the highest ethanol yield with mild lime addition (60% of theoretical) vs. steam alone (53%). However, modest yields were generally evidenced (average, 55%) as a result of high viscosity, especially in the case of high lime dose in SSF at high solid concentration. Combined energy yield (ethanol, methane and solid residue) proved lime effectiveness as catalyst in steam explosion of SB, beside two intrinsic advantages: low water consumption in SSF at high solid concentration, and the possibility of lime removal from downstream effluents through carbonation. (C) 2015 Elsevier B.V. All rights reserved.
  •  
22.
  • 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
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23.
  • Carrasco, Cristhian, et al. (författare)
  • Fermentation of the Straw Material Paja Brava by the Yeast Pichia stipitis in a Simultaneous Saccharification and Fermentation Process
  • 2013
  • Ingår i: Journal of Sustainable Bioenergy Systems. - : Scientific Research Publishing, Inc.. - 2165-4018 .- 2165-400X. ; 3:2, s. 99-106
  • Tidskriftsartikel (refereegranskat)abstract
    • Paja Brava is a native South American grass with a high carbohydrate content. In the current work, the potential of us- ing this feedstock for ethanol production using a simultaneous saccharification and fermentation (SSF) process with the xylose-fermenting yeast Pichia stipitis (Scheffersomyces stipitis) CBS6054 was investigated. The straw material was subjected to SO2 catalyzed steam pretreatment at 200°C and 5 min residence time, which resulted in a solubilization of pentose sugars (mainly xylose) of 64% with only minor amounts of degradation products. The obtained material, in- cluding the pretreatment liquid, was subsequently hydrolyzed and fermented in an SSF process at microaerobic condi- tions using either a batch or a fed-batch process at a total water-insoluble solids loading of 10%. Overall yields of etha- nol based on all available sugars of 0.24 g/g and 0.27 g/g were obtained for batch and fed-batch mode of operation, re- spectively. The higher yield in the fed-batch process coincided with a higher degree of conversion of the sugars in the liquid medium, in particular of arabinose, for which the conversion was doubled (from 48% to 97%).
  •  
24.
  • 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
  •  
25.
  • 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.
  •  
26.
  • 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.
  •  
27.
  • Choteborska, P, et al. (författare)
  • Processing of wheat bran to sugar solution
  • 2004
  • Ingår i: Journal of Food Engineering. - 0260-8774. ; 61:4, s. 561-565
  • Tidskriftsartikel (refereegranskat)abstract
    • In accordance to better exploitation of raw material for bioethanol production we try to find the method for saccharification of problematic cover part of grain, so called bran. The bran consists of three main components: residual starch, hemicellulose and cellulose. Whereas hydrolysis of starch is easy and well solved, there are questions how to optimise hydrolysis of all polysaccharides together, including hernicellulose and cellulose. The bran was treated with starch degrading enzymes (Termamyl 120 L and AMG 300 L) in order to remove the starch from the solid particles and use the starch-free residue for hydrolysis of hernicelluloses to pentoses. This starch-free residue (SFR) was treated with sulphuric acid and high temperature during exact time. Different times of pre-treatment (10-50 min), different temperatures (110-180degreesC) and different concentrations of sulphuric acid (1-4% of weight of slurry) were tested, as well as presence of furfural and 5-hydroxy-methyl-2-furaldehyd (HMF), substances causing inhibition of fermentation, was evaluated. The best yield of sugars (52.1 g/100 g of SFR) was achieved by using 1% of sulphuric acid at 130degreesC for 40 min and this method generates very low content of furfural and HMF (0.28 g/l, resp. 0.05 g/l). (C) 2003 Elsevier Ltd. All rights reserved.
  •  
28.
  • Eklund, R, et al. (författare)
  • Optimization of temperature and enzyme concentration in the enzymatic saccharification of steam-pretreated willow
  • 1990
  • Ingår i: Enzyme and Microbial Technology. - 0141-0229. ; 12:3, s. 225-228
  • Tidskriftsartikel (refereegranskat)abstract
    • The effect of temperature and enzyme concentration on the enzymatic hydrolysis of steam-pretreated willow was investigated to obtain the optimal hydrolysis conditions. The willow was pretreated at 220°C for 10 min according to the results of earlier optimization studies of the steam-pretreatment conditions for high glucose yields. The concentrations of two commercial enzymes, Celluclast 2L and Novozyme 188, were varied in the range 0–20% (based on oven-dry substrate). A maximum in the conversion of cellulose to glucose was obtained using a mixture of 15% Celluclast and 3% Novozyme, corresponding to an activity of 11.4 FPU g−1 substrate. Higher enzyme concentrations did not increase the initial hydrolysis rate nor affect the final glucose yield. The effects of temperature in the range 40°C to 60°C were investigated. The temperature affects both the initial hydrolysis rate and the final glucose yield. The highest glucose yield was obtained at 40°C. The yield decreased with increasing temperature, due to increased enzyme deactivation at higher temperatures, while the initial reaction rate increased with increasing temperatures.
  •  
29.
  •  
30.
  • Eklund, R, et al. (författare)
  • The Influence of SO2 and H2SO4 Impregnation of Willow Prior to Steam Pretreatment
  • 1995
  • Ingår i: Bioresource Technology. - 1873-2976. ; 52:3, s. 225-229
  • Tidskriftsartikel (refereegranskat)abstract
    • In this investigation steam pretreatment of willow with the addition of SO2 or H2SO4 was studied, the aim being to recover both the cellulose and the hemicellulose fr actions. The willow was steamed (1 bar saturated steam) prior to impregnation with 0-3% H2SO4 or 1% SO2 (w/w substrate). The pretreatment experiments were performed at temperatures in the range 160-230 degrees C for 10 min. The highest xylose recovery with H2SO4 impregnation was obtained using 3% H2SO4 at 190 degrees C, where 80% of the available xylose could be recovered by washing. At these pretreatment conditions, a glucose yield after enzymatic hydrolysis of 67%, based on the glucan available in the raw material, was achieved. The maximum glucose yield, 95%, was obtained when the willow was impregnated with 1% SO2 and pretreated at 200 degrees C. At these conditions, 62% of the original xylose was solubilized. As glucan is the main constituent of willow, a high yield of glucose is of more importance than a high yield of xylose, leading to the conclusion that impregnation with SO2 is better than impregnation with H2SO4.
  •  
31.
  • Eklund, R, et al. (författare)
  • Two-stage steam pretreatment of willow for increased pentose yield
  • 1988
  • Ingår i: Journal of Wood Chemistry and Technology. - : Informa UK Limited. - 0277-3813 .- 1532-2319. ; 8:3, s. 379-392
  • Tidskriftsartikel (refereegranskat)abstract
    • A two-stage procedure for pretreatment of fast-growing willow with steam has been investigated. The first stage was performed at temperatures in the range 180°C to 220°C for times between 6 and 10 minutes while the second stage was performed at 220°C for 10 minutes. The fibrous material was washed between the two stages to remove the pentosans and thus increase the pentose yield. The pretreatment was assessed in terms of glucose yield and xylose yield in the subsequent enzymatic hydrolysis. The maximum yields, around 70% for both glucose and xylose, were obtained for a pretreatment temperature of 200°C in the first stage. The major part of the xylose was found in the first rinsing water while almost all the glucose was recovered from the final fibrous material. The glucose yield was increased to above 80% when wet material (30% ODM) was used in the first stage. This required a modification of the steam pretreatment unit, allowing for condensate removal during steaming. The results are very promising but further investigations are needed to optimize the process.
  •  
32.
  • Erdei, Borbala, et al. (författare)
  • Ethanol production from mixtures of wheat straw and wheat meal
  • 2010
  • Ingår i: Biotechnology for Biofuels. - : Springer Science and Business Media LLC. - 1754-6834. ; 3
  • Tidskriftsartikel (refereegranskat)abstract
    • Background: Bioethanol can be produced from sugar-rich, starch-rich (first generation; 1G) or lignocellulosic (second generation; 2G) raw materials. Integration of 2G ethanol with 1G could facilitate the introduction of the 2G technology. The capital cost per ton of fuel produced would be diminished and better utilization of the biomass can be achieved. It would, furthermore, decrease the energy demand of 2G ethanol production and also provide both 1G and 2G plants with heat and electricity. In the current study, steam-pretreated wheat straw (SPWS) was mixed with presaccharified wheat meal (PWM) and converted to ethanol in simultaneous saccharification and fermentation (SSF). Results: Both the ethanol concentration and the ethanol yield increased with increasing amounts of PWM in mixtures with SPWS. The maximum ethanol yield (99% of the theoretical yield, based on the available C6 sugars) was obtained with a mixture of SPWS containing 2.5% water-insoluble solids (WIS) and PWM containing 2.5% WIS, resulting in an ethanol concentration of 56.5 g/L. This yield was higher than those obtained with SSF of either SPWS (68%) or PWM alone (91%). Conclusions: Mixing wheat straw with wheat meal would be beneficial for both 1G and 2G ethanol production. However, increasing the proportion of WIS as wheat straw and the possibility of consuming the xylose fraction with a pentose-fermenting yeast should be further investigated.
  •  
33.
  • Erdei, Borbala, et al. (författare)
  • Glucose and xylose co-fermentation of pretreated wheat straw using mutants of S. cerevisiae TMB3400.
  • 2013
  • Ingår i: Journal of Biotechnology. - : Elsevier BV. - 1873-4863 .- 0168-1656. ; 164:1, s. 50-58
  • Tidskriftsartikel (refereegranskat)abstract
    • Wheat straw was pretreated and fermented to ethanol. Two strains, which had been mutated from the genetically modified Saccharomyces cerevisiae TMB3400, KE6-12 and KE6-13i, have been used in this study and the results of performance were compared to that of the original strain. The glucose and xylose co-fermentation ability was investigated in batch fermentation of steam-pretreated wheat straw (SPWS) liquid (undiluted, and diluted 1.5 and 2 times). Both strains showed improved xylose uptake in diluted SPWS liquid, and increased ethanol yields compared with the original TMB3400 strain, although xylitol formation also increased slightly. In undiluted SPWS liquid, however, only KE6-13i performed better than the original strain regarding xylose utilization. Fed-batch fermentation of 1.5 and 2 times diluted liquid was performed by adding the glucose-rich hydrolysates from enzymatic hydrolysis of the solid fraction of SPWS at a constant feed rate after 5h of fermentation, when the glucose had been depleted. The modified strains showed improved xylose conversion; however, the ethanol yield was not significantly improved due to increased glycerol production. Fed-batch fermentation resulted in faster xylose utilization than in the batch cases.
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34.
  • Erdei, Borbala, et al. (författare)
  • Separate hydrolysis and co-fermentation for improved xylose utilization in integrated ethanol production from wheat meal and wheat straw
  • 2012
  • Ingår i: Biotechnology for Biofuels. - : Springer Science and Business Media LLC. - 1754-6834. ; 5
  • Tidskriftsartikel (refereegranskat)abstract
    • Background: The commercialization of second-generation bioethanol has not been realized due to several factors, including poor biomass utilization and high production cost. It is generally accepted that the most important parameters in reducing the production cost are the ethanol yield and the ethanol concentration in the fermentation broth. Agricultural residues contain large amounts of hemicellulose, and the utilization of xylose is thus a plausible way to improve the concentration and yield of ethanol during fermentation. Most naturally occurring ethanol-fermenting microorganisms do not utilize xylose, but a genetically modified yeast strain, TMB3400, has the ability to co-ferment glucose and xylose. However, the xylose uptake rate is only enhanced when the glucose concentration is low. Results: Separate hydrolysis and co-fermentation of steam-pretreated wheat straw (SPWS) combined with wheat-starch hydrolysate feed was performed in two separate processes. The average yield of ethanol and the xylose consumption reached 86% and 69%, respectively, when the hydrolysate of the enzymatically hydrolyzed (18.5% WIS) unwashed SPWS solid fraction and wheat-starch hydrolysate were fed to the fermentor after 1 h of fermentation of the SPWS liquid fraction. In the other configuration, fermentation of the SPWS hydrolysate (7.0% WIS), resulted in an average ethanol yield of 93% from fermentation based on glucose and xylose and complete xylose consumption when wheat-starch hydrolysate was included in the feed. Increased initial cell density in the fermentation (from 5 to 20 g/L) did not increase the ethanol yield, but improved and accelerated xylose consumption in both cases. Conclusions: Higher ethanol yield has been achieved in co-fermentation of xylose and glucose in SPWS hydrolysate when wheat-starch hydrolysate was used as feed, then in co-fermentation of the liquid fraction of SPWS fed with the mixed hydrolysates. Integration of first-generation and second-generation processes also increases the ethanol concentration, resulting in a reduction in the cost of the distillation step, thus improving the process economics.
  •  
35.
  • Erdei, Borbala, et al. (författare)
  • Simultaneous saccharification and co-fermentation of whole wheat in integrated ethanol production
  • 2013
  • Ingår i: Biomass & Bioenergy. - : Elsevier BV. - 1873-2909 .- 0961-9534. ; 56, s. 506-514
  • Tidskriftsartikel (refereegranskat)abstract
    • Two of the most important ways of reducing the production cost of lignocellulosic ethanol are to increase the ethanol yield and the concentration in the fermentation broth. This can be facilitated by co-fermentation of glucose and xylose from agricultural residues such as wheat straw, due to the high amount of xylose in the hemicelluloses in these materials. Simultaneous saccharification and co-fermentation (SSCF) of steam-pretreated wheat straw (SPWS) with and without the addition of liquefied wheat meal (LWM) was performed using the pentose-fermenting yeast, TMB3400. The highest overall ethanol yield in batch operation, of around 70%, equivalent to an ethanol concentration of 43.7 g L-1, was achieved using SPWS with 7.5% water-insoluble solids (WIS) and addition of LWM with 1% WIS. Using SPWS with a higher WIS (10%) resulted in a decreased yield, 60%, although the concentration of ethanol increased to 53.0 g L-1. SSCF of 7.5% straw was also performed with a single (after 20 h) or fed-batch addition of 1% WIS LWM (after 20, 24 and 28 h) resulting in an increase in both ethanol yield and concentration compared to the reference, without wheat meal addition, but no significant difference compared to the batch experiments. The addition of wheat meal to SSCF did not improve xylose utilization significantly, probably due to the instant release of glucose from the liquefied meal, which hampers the uptake of xylose. The instant release of glucose was shown to be caused by the high amylase activity of the beta-glucosidase enzyme preparation. (C) 2013 Elsevier Ltd. All rights reserved.
  •  
36.
  • Erdei, Borbala, et al. (författare)
  • SSF of steam-pretreated wheat straw with the addition of saccharified or fermented wheat meal in integrated bioethanol production
  • 2013
  • Ingår i: Biotechnology for Biofuels. - : Springer Science and Business Media LLC. - 1754-6834. ; 6
  • Tidskriftsartikel (refereegranskat)abstract
    • Background: Integration of second-generation (2G) bioethanol production with existing first-generation (1G) production may facilitate commercial production of ethanol from cellulosic material. Since 2G hydrolysates have a low sugar concentration and 1G streams often have to be diluted prior to fermentation, mixing of streams is beneficial. Improved ethanol concentrations in the 2G production process lowers energy demand in distillation, improves overall energy efficiency and thus lower production cost. There is also a potential to reach higher ethanol yields, which is required in economically feasible ethanol production. Integrated process scenarios with addition of saccharified wheat meal (SWM) or fermented wheat meal (FWM) were investigated in simultaneous saccharification and (co-)fermentation (SSF or SSCF) of steam-pretreated wheat straw, while the possibility of recovering the valuable protein-rich fibre residue from the wheat was also studied. Results: The addition of SWM to SSF of steam-pretreated wheat straw, using commercially used dried baker's yeast, S. cerevisiae, resulted in ethanol concentrations of about 60 g/L, equivalent to ethanol yields of about 90% of the theoretical. The addition of FWM in batch mode SSF was toxic to baker's yeast, due to the ethanol content of FWM, resulting in a very low yield and high accumulation of glucose. The addition of FWM in fed-batch mode still caused a slight accumulation of glucose, but the ethanol concentration was fairly high, 51.2 g/L, corresponding to an ethanol yield of 90%, based on the amount of glucose added. In batch mode of SSCF using the xylose-fermenting, genetically modified S. cerevisiae strain KE6-12, no improvement was observed in ethanol yield or concentration, compared with baker's yeast, despite the increased xylose utilization, probably due to the considerable increase in glycerol production. A slight increase in xylose consumption was seen when glucose from SWM was fed at a low feed rate, after 48 hours, compared with batch SSCF. However, the ethanol yield and concentration remained in the same range as in batch mode. Conclusion: Ethanol concentrations of about 6% (w/v) were obtained, which will result in a significant reduction in the cost of downstream processing, compared with SSF of the lignocellulosic substrate alone. As an additional benefit, it is also possible to recover the protein-rich residue from the SWM in the process configurations presented, providing a valuable co-product.
  •  
37.
  • Frankó, Balázs, et al. (författare)
  • Bioethanol production from forestry residues : A comparative techno-economic analysis
  • 2016
  • Ingår i: Applied Energy. - : Elsevier BV. - 0306-2619. ; 184, s. 727-736
  • Tidskriftsartikel (refereegranskat)abstract
    • A techno-economic analysis was conducted to assess the feasibility of using forestry residues with different bark contents for bioethanol production. A proposed cellulosic ethanol biorefinery in Sweden was simulated with Aspen Plus. The plant was assumed to convert different forestry assortments (sawdust and shavings, fuel logs, early thinnings, tops and branches, hog fuel and pulpwood) to ethanol, pellets, biogas and electricity. The intention was not to obtain absolute ethanol production costs for future facilities, but to assess and compare the future potential of utilizing different forestry residues for bioethanol production. The same plant design and operating conditions were assumed in all cases, and the effect of including bark on the whole conversion process, especially how it influenced the ethanol production cost, was studied. While the energy efficiency (not including district heating) obtained for the whole process was between 67 and 69% regardless of the raw material used, the ethanol production cost differed considerably; the minimum ethanol selling price ranging from 0.77 to 1.52 USD/L. Under the basic assumptions, all the forestry residues apart from sawdust and shavings exhibited a negative net present value at current market prices. The profitability decreased with increasing bark content of the raw material. Sensitivity analyses showed that, at current market prices, the utilization of bark-containing forestry residues will not provide significant cost improvement compared with pulpwood unless the conversion of cellulose and hemicellulose to monomeric sugars is improved.
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38.
  • Franko, Balazs, et al. (författare)
  • Influence of bark on fuel ethanol production from steam-pretreated spruce.
  • 2015
  • Ingår i: Biotechnology for Biofuels. - : Springer Science and Business Media LLC. - 1754-6834. ; 8
  • Tidskriftsartikel (refereegranskat)abstract
    • Bark and bark-containing forest residues have the potential for utilization as raw material for lignocellulosic ethanol production due to their abundance and low cost. However, the different physical properties and chemical composition of bark compared to the conventionally used wood chips may influence the spruce-to-ethanol bioconversion process. This study assesses the impact of bark on the overall bioconversion in two process configurations, separate hydrolysis and fermentation (SHF) and simultaneous saccharification and fermentation (SSF), utilizing steam-pretreated spruce bark and wood mixtures.
  •  
39.
  • Frankó, Balázs, et al. (författare)
  • Removal of Water-Soluble Extractives Improves the Enzymatic Digestibility of Steam-Pretreated Softwood Barks
  • 2018
  • Ingår i: Applied Biochemistry and Biotechnology. - : Springer Science and Business Media LLC. - 0273-2289 .- 1559-0291. ; 184:2, s. 599-615
  • Tidskriftsartikel (refereegranskat)abstract
    • Softwood bark contains a large amounts of extractives—i.e., soluble lipophilic (such as resin acids) and hydrophilic components (phenolic compounds, stilbenes). The effects of the partial removal of water-soluble extractives before acid-catalyzed steam pretreatment on enzymatic digestibility were assessed for two softwood barks—Norway spruce and Scots pine. A simple hot water extraction step removed more than half of the water-soluble extractives from the barks, which improved the enzymatic digestibility of both steam-pretreated materials. This effect was more pronounced for the spruce than the pine bark, as evidenced by the 30 and 11% glucose yield improvement, respectively, in the enzymatic digestibility. Furthermore, analysis of the chemical composition showed that the acid-insoluble lignin content of the pretreated materials decreased when water-soluble extractives were removed prior to steam pretreatment. This can be explained by a decreased formation of water-insoluble “pseudo-lignin” from water-soluble bark phenolics during the acid-catalyzed pretreatment, which otherwise results in distorted lignin analysis and may also contribute to the impaired enzymatic digestibility of the barks. Thus, this study advocates the removal of extractives as the first step in the processing of bark or bark-rich materials in a sugar platform biorefinery.
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40.
  •  
41.
  • Frankó, Balázs, et al. (författare)
  • The effect of blending spruce and poplar on acid-catalyzed steam pretreatment and enzymatic hydrolysis
  • 2019
  • Ingår i: Bioresource Technology Reports. - : Elsevier BV. - 2589-014X. ; 7
  • Tidskriftsartikel (refereegranskat)abstract
    • The aim of this work was to explore the possibility of mixed feedstocks utilization using acid-catalyzed steam pretreatment in the context of forest biomass. Three steam pretreatment conditions were applied to characterize the interactions between spruce (softwood) and poplar (hardwood) that were concurrently processed by SO2-catalyzed steam pretreatment and enzymatic hydrolysis. The effects of blending feedstocks were evaluated in terms of composition and enzymatic digestibility. The combined sugar yields after steam pretreatment and enzymatic hydrolysis ranged from 58% to 71%. No synergistic or antagonistic interactions were observed in the concurrent use of spruce and poplar—our linear interpolation model accurately predicted the overall sugar recovery after steam pretreatment and enzymatic hydrolysis for a 50:50 blend to within 3%, based on the results of the individual feedstocks.
  •  
42.
  • Galbe, Mats, et al. (författare)
  • A review of the production of ethanol from softwood
  • 2002
  • Ingår i: Applied Microbiology and Biotechnology. - : Springer Science and Business Media LLC. - 1432-0614 .- 0175-7598. ; 59:6, s. 618-628
  • Forskningsöversikt (refereegranskat)abstract
    • Ethanol produced from various lignocellulosic materials such as wood, agricultural and forest residues has the potential to be a valuable substitute for, or complement to, gasoline. One of the major resources in the Northern hemisphere is softwood. This paper reviews the current status of the technology for ethanol production from softwood, with focus on hemicellulose and cellulose hydrolysis, which is the major problem in the overall process. Other issues of importance, e.g. overall process configurations and process economics are also considered.
  •  
43.
  • Galbe, Mats, et al. (författare)
  • Adsorption of cellulases on steam-pretreated willow
  • 1990
  • Ingår i: Applied Biochemistry and Biotechnology. - 1559-0291. ; 24-5, s. 87-101
  • Tidskriftsartikel (refereegranskat)abstract
    • The adsorption of cellulases on steam-pretreated willow has been measured for2, 4, and 8 wt% willow and with varying enzyme concentrations (2–100 wt% based on substrate). The enzyme concentration was measured as soluble protein, filter paper activity (FPA), CMC-ase activity, and activity toward willow. The adsorption data were modeled with a Langmuir isotherm. The maximum adsorption capability depends on the method for measurement of the enzyme concentration. The lowest value, 470 mg enzyme/g willow, was obtained for the soluble protein and the highest value, 650 mg/g, for the FPA. For technical applications, a single isotherm can be used for calculation of the adsorption capability of steam-treated willow.
  •  
44.
  • Galbe, Mats, et al. (författare)
  • Cellulosic Bioethanol Production
  • 2013
  • Ingår i: Separation and Purification Technologies in Biorefineries. - Chichester, UK : John Wiley & Sons, Ltd. - 9780470977965 - 9781118493441 ; , s. 487-501
  • Bokkapitel (refereegranskat)abstract
    • This chapter discusses some aspects of various separation technologies applied in bioethanol production from lignocellulosic materials. Bioethanol can be produced from lignocellulosic biomass using several different process configurations. The main energy-demanding process steps in lignocellulosic ethanol production are distillation to concentrate the ethanol, adsorption to remove the final content of water, and, optionally, evaporation either of the sugar solution before fermentation or of the stillage stream, as an option to anaerobic digestion, and drying of the solid residue, if this is required. The dehydration of ethanol using adsorption on zeolites is performed in two packed columns, where one is adsorbing water while the other is regenerated. One of the most important issues is to verify all process steps in an integrated way at a pilot and/or demonstration scale. The step from pilot- and demonstration-scale production of lignocellulosic ethanol to competitive full-scale production requires further reduction of the production cost.
  •  
45.
  • Galbe, Mats, et al. (författare)
  • Pretreatment for biorefineries : A review of common methods for efficient utilisation of lignocellulosic materials
  • 2019
  • Ingår i: Biotechnology for Biofuels. - : Springer Science and Business Media LLC. - 1754-6834. ; 12:1
  • Forskningsöversikt (refereegranskat)abstract
    • The implementation of biorefineries based on lignocellulosic materials as an alternative to fossil-based refineries calls for efficient methods for fractionation and recovery of the products. The focus for the biorefinery concept for utilisation of biomass has shifted, from design of more or less energy-driven biorefineries, to much more versatile facilities where chemicals and energy carriers can be produced. The sugar-based biorefinery platform requires pretreatment of lignocellulosic materials, which can be very recalcitrant, to improve further processing through enzymatic hydrolysis, and for other downstream unit operations. This review summarises the development in the field of pretreatment (and to some extent, of fractionation) of various lignocellulosic materials. The number of publications indicates that biomass pretreatment plays a very important role for the biorefinery concept to be realised in full scale. The traditional pretreatment methods, for example, steam pretreatment (explosion), organosolv and hydrothermal treatment are covered in the review. In addition, the rapidly increasing interest for chemical treatment employing ionic liquids and deep-eutectic solvents are discussed and reviewed. It can be concluded that the huge variation of lignocellulosic materials makes it difficult to find a general process design for a biorefinery. Therefore, it is difficult to define "the best pretreatment" method. In the end, this depends on the proposed application, and any recommendation of a suitable pretreatment method must be based on a thorough techno-economic evaluation.
  •  
46.
  • Galbe, Mats, et al. (författare)
  • Pretreatment of Lignocellulosic Materials for Efficient Bioethanol Production
  • 2007
  • Ingår i: Advances in Biochemical Engineering/Biotechnology. - Berlin, Heidelberg : Springer Berlin Heidelberg. - 0724-6145. - 9783540736509 ; 108, s. 41-65
  • Bokkapitel (refereegranskat)abstract
    • Second-generation bioethanol produced from various lignocellulosic materials, such as wood, agricultural or forest residues, has the potential to be a valuable substitute for, or a complement to, gasoline. One of the crucial steps in the ethanol production is the hydrolysis of the hemicellulose and cellulose to monomer sugars. The most promising method for hydrolysis of cellulose to glucose is by use of enzymes, i.e. cellulases. However, in order to make the raw material accessible to the enzymes some kind of pretreatment is necessary. During the last few years a large number of pretreatment methods have been developed, comprising methods working at low pH, i.e. acid based, medium pH (without addition of catalysts), and high pH, i.e. with a base as catalyst. Many methods have been shown to result in high sugar yields, above 90% of theoretical for agricultural residues, especially for corn stover. For more recalcitrant materials, e.g. softwood, acid hydrolysis and steam pretreatment with acid catalyst seem to be the methods that can be used to obtain high sugar and ethanol yields. However, for more accurate comparison of different pretreatment methods it is necessary to improve the assessment methods under real process conditions. The whole process must be considered when a performance evaluation is to be made, as the various pretreatment methods give different types of materials. (Hemicellulose sugars can be obtained either in the liquid as monomer or oligomer sugars, or in the solid material to various extents; lignin can be either in the liquid or remain in the solid part; the composition and amount/concentration of possible inhibitory compounds also vary.) This will affect how the enzymatic hydrolysis should be performed(e.g. with or without hemicellulases), how the lignin is recovered and also the use of the lignin co-product.
  •  
47.
  • Galbe, Mats, et al. (författare)
  • Pretreatment: The key to efficient utilization of lignocellulosic materials
  • 2012
  • Ingår i: Biomass & Bioenergy. - : Elsevier BV. - 1873-2909 .- 0961-9534. ; 46, s. 70-78
  • Tidskriftsartikel (refereegranskat)abstract
    • Second-generation ethanol production from various lignocellulosic materials based on enzymatic hydrolysis of cellulose has moved from research in lab scale to pilot- and demo scale but has not yet reached commercial scale. One of the crucial process steps is the pretreatment of the biomass, which has as primary aim to make the biomass accessible to enzymatic attack, as it has a large impact on all the other steps in the process. Several pretreatment methods have been developed, comprising methods working at low pH, i.e., acid based, at medium pH (without addition of catalysts), or at high pH, i.e., with a base as catalyst. Many methods result in high sugar yields, above 90% of theoretical for agricultural residues while more recalcitrant materials like hardwood, and especially softwood, require dilute-acid pretreatment to reach high sugar yields. However, most studies on pretreatment have been assessed by enzymatic hydrolysis at low solids content and high enzyme dosages. The various pretreatment methods need in the future to be reassessed at more industrial-like conditions considering the whole integrated process taking into consideration the influence on all process steps. In this review, various pretreatment methods are discussed and how assessment should be performed to reach optimal conditions. (C) 2012 Elsevier Ltd. All rights reserved.
  •  
48.
  • Galbe, Mats, et al. (författare)
  • Process Engineering Economics of Bioethanol Production
  • 2007
  • Ingår i: Advances in Biochemical Engineering/Biotechnology. - Berlin, Heidelberg : Springer Berlin Heidelberg. - 0724-6145. - 9783540736509 ; 108, s. 303-327
  • Bokkapitel (refereegranskat)abstract
    • This work presents a review of studies on the process economics of ethanol production from lignocellulosic materials published since 1996. Our objective was to identify the most costly process steps and the impact of various parameters on the fi- nal production cost, e.g. plant capacity, raw material cost, and overall product yield, as well as process configuration. The variation in estimated ethanol production cost is considerable, ranging from about 0.13 to 0.81 US$ per liter ethanol. This can be explained to a large extent by actual process differences and variations in the assumptions underlying the techno-economic evaluations. The most important parameters for the economic outcome are the feedstock cost, which varied between 30 and 90US$ per metric ton in the papers studied, and the plant capacity, which influences the capital cost. To reduce the ethanol production cost it is necessary to reach high ethanol yields, as well as a high ethanol concentration during fermentation, to be able to decrease the energy required for distillation and other downstream process steps. Improved pretreatment methods, enhanced enzymatic hydrolysis with cheaper and more effective enzymes, as well as improved fermentation systems present major research challenges if we are to make lignocellulose-based ethanol production competitive with sugar- and starch-based ethanol. Process integration, either internally or externally with other types of plants, e.g. heat and power plants, also offers a way of reducing the final ethanol production cost.
  •  
49.
  • Galbe, Mats, et al. (författare)
  • Production of ethanol from biomass - Research in Sweden
  • 2005
  • Ingår i: Journal of Scientific and Industrial Research. - 0022-4456. ; 64:11, s. 905-919
  • Tidskriftsartikel (refereegranskat)abstract
    • Ethanol produced from various lignocellulosic materials such as wood, agricultural and forest residues has the potential to be a valuable substitute for, or complement to, gasoline. This paper reviews the research activities in Sweden on development of the technology for ethanol production from lignocellulosics. The paper focuses on hemicellulose and cellulose hydrolysis and fermentation as well as on process integration and techno-economic evaluation of the overall process.
  •  
50.
  • Galbe, Mats, et al. (författare)
  • Simulation of ethanol production processes based on enzymatic hydrolysis of lignocellulosic materials using ASPEN PLUS
  • 1992
  • Ingår i: Applied Biochemistry and Biotechnology. - 1559-0291. ; 34-5, s. 93-104
  • Tidskriftsartikel (refereegranskat)abstract
    • The process simulator ASPEN PLUS was used for simulation of an ethanol production process based on enzymatic hydrolysis of lignocellulosic materials. The effect of water recycling, necessary to reduce the amount of waste water and to increase the ethanol concentration in the feed to the distillation, was investigated. For a process based on 20 t/h raw material, the amount of waste water can be reduced from 70.7 t/h, without recycling, to 7.1 t/h. Furthermore, the ethanol concentration in the distillation feed increased from 2.5 to 10%. The concentration of byproducts and possible inhibitors increased by a factor of 20-40 in the hydrolysis and fermentation steps. This gives new conditions for future hydrolysis and fermentation experiments.
  •  
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