| 1. |
- Reczey, K, et al.
(författare)
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Cellulase production by T-reesei
- 1996
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Ingår i: Bioresource Technology. - : Elsevier BV. - 1873-2976 .- 0960-8524. ; 57:1, s. 25-30
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Tidskriftsartikel (refereegranskat)abstract
- Steam-pretreated willow has been found to be a suitable substrate for ethanol production in Sweden. The production of Trichoderma reesei cellulases on steam-pretreated willow (SPW) of varying cellulose content has been studied. Batch fermentations were performed in shake flasks, and in 4- and 22-l fermenters. SPW was found to be a suitable carbon source for cellulase production. At an initial solids concentration corresponding to 10 g/l cellulose, the yield was 108 filter paper units (FPU)/g cellulose after 3 days in the 22-l fermenter However, the yield was below 100 FPU/g cellulose in the shake flasks and 4-l fermenter The solid residue of enzymatically hydrolysed SPW was found to be nearly as good a substrate as SPW, although the cellulose content was as low as 20% in this hydrolysis residue. Using delignified SPW, the yield of cellulases was low, indicating that lignin does not inhibit cellulase production. By applying a pressure of 1.7 bar in the fermenter, the initial fermentation rate was increased. The productivity was increased from 12.2 FPU/l/h to 16.7 FPU/l/h, due to the higher level of dissolved oxygen at the higher pressure. Copyright (C) 1996 Elsevier Science Ltd.
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| 2. |
- von Sivers, M, et al.
(författare)
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Ethanol from lignocellulosics: A review of the economy
- 1996
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Ingår i: Bioresource Technology. - : Elsevier BV. - 1873-2976 .- 0960-8524. ; 56:2-3, s. 131-140
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Tidskriftsartikel (refereegranskat)abstract
- The present study is a review of published investigations regarding the economy of ethanol production from lignocellulosic material The objective is to present relations between and tendencies observed in different cost estimates. The influence of plant capacity and overall product yield on the ethanol production cost is investigated, as well as variations in capital costs in the different processes. The underlying technical and economic assumptions show a large variation between the various studies published. The variation in the ethanol production cost is large, from 18 to 151 US cent/l. The most important factor for the economic outcome is the overall ethanol yield. Other important parameters are the feedstock cost, which was found to vary between 22 and 61 US$/dry metric ton, and the plant capacity, which influences the capital cost. It is shown that there is a tendency towards a decrease in ethanol production cost with an increase in plant capacity for the enzymatic processes. A high yield also results in a decrease in production cost for the enzymatic and dilute acid processes in the papers reviewed. Copyright (C) 1996 Elsevier Science Ltd.
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| 3. |
- Christakopoulos, Paul, et al.
(författare)
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Direct conversion of sorghum carbohydrates to ethanol by a mixed microbial culture
- 1993
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Ingår i: Bioresource Technology. - 0960-8524 .- 1873-2976. ; 45:2, s. 89-92
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Tidskriftsartikel (refereegranskat)abstract
- The carbohydrates of sweet sorghum were directly converted to ethanol by a mixed culture of Fusarium oxysporum F3 and Saccharomyces cerevisiae 2541. A number of factors affecting this bioconversion was studied. Optimum ethanol yields of 33·2 g/100 g of total sorghum carbohydrates, corresponding to 10·3 g/100 g of fresh stalks, were obtained. These values represented 68·6% of the theoretical yield based on total polysaccharides and exceeded that based on oligosaccharides of sorghum by 53·7%. The results demonstrated that more than half of the sorghum polysaccharides were directly fermented to ethanol, thus making the process worthy of further investigation.
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| 4. |
- Christakopoulos, Paul, et al.
(författare)
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Direct ethanol conversion of pretreated straw by Fusarium oxysporum
- 1991
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Ingår i: Bioresource Technology. - : Elsevier BV. - 0960-8524 .- 1873-2976. ; 35:3, s. 297-300
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Tidskriftsartikel (refereegranskat)abstract
- Factors affecting the direct conversion of alkali pretreated straw to ethanol by Fusarium oxysporum F3 were investigated and the alkali level used for pretreatment and the degree of delignification of straw were found to be the most important. A linear correlation between ethanol yield and both the degree of straw delignification and the alkali level was observed. At optimum delignified straw concentration (4% w/v), a maximum ethanol yield of 0·275 g ethanol g−1 of straw was obtained corresponding to 67·8% of the theoretical yield.
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| 5. |
- Christakopoulos, Paul, et al.
(författare)
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Production and partial characterization of xylanase from Fusarium oxysporum
- 1996
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Ingår i: Bioresource Technology. - 0960-8524 .- 1873-2976. ; 58:2, s. 115-119
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Tidskriftsartikel (refereegranskat)abstract
- Production of xylanase by Fusarium oxysporum strain F3 was enhanced by optimization of initial pH of the culture medium, the type and concentration of nitrogen and carbon source, and the growth temperature. Under these conditions, yields as high as 245 U/ml of culture medium were obtained. The most important characteristic of the enzyme is its high pH stability. It retained 80 and 66% of the activity at pH 9.0 after 24 h at 4 and 30°C, respectively. Chromogenic (fluorogenic) 4-methylumbelliferyl-β-glycosides of xylose (MUX) and xylobiose (MUX2) were used to characterize xylanase multienzyme components, after separation by isoelectric focusing. The zymogram indicated one major, one minor xylanase and one active β-xylosidase exhibiting pI values of 9.5, 6.5 and 3.8, respectively
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| 6. |
- Kalogeris, E, et al.
(författare)
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Performance of an intermittent agitation rotating drum type bioreactor for solid-state fermentation of wheat straw
- 2003
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Ingår i: Bioresource Technology. - 0960-8524 .- 1873-2976. ; 86:3, s. 207-213
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Tidskriftsartikel (refereegranskat)abstract
- A laboratory bioreactor, designed for solid-state fermentation of thermophilic microorganisms, was operated for production of cellulases and hemicellulases by the thermophilic fungus Thermoascus aurantiacus. The suitability of the apparatus for the effective control of important operating variables affecting growth of microbes in solid-state cultivation was determined. Application of the optimum conditions found for the moisture content of the medium, growth temperature and airflow rate produced enzyme yields of 1709 U endoglucanase, 4 U cellobiohydrolase, 79 U β-glucosidase, 5.5 U FPA, 4490 U xylanase and 45 U β-xylosidase per g of dry wheat straw. The correlation between microorganism growth and production of enzymes was efficiently described by the Le Duy kinetic model. © 2002 Elsevier Science Ltd. All rights reserved.
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| 7. |
- Rodhe, Lena
(författare)
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Methods for determining the presence of slurry on the crop and in the upper soil layer after application to grassland
- 2003
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Ingår i: Bioresource Technology. - 0960-8524 .- 1873-2976. ; 90:1, s. 81-88
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Tidskriftsartikel (refereegranskat)abstract
- Slurry injection in grassland may lead to lower ammonia losses and enhance silage quality compared to surface spreading. In order to evaluate the performance of different slurry injectors, there is a need for methods which measure the degree of crop contamination and the position of the slurry in the soil after spreading. The aim of this study was to identify and test possible methods. The amount of cattle slurry present on the grass stubble after spreading was determined by measuring the electrical conductivity of water used for rinsing grass samples. The slurry placement in the soil profile was measured in cross-sections made through the slurry trails. Methods used were analyses of images taken by different cameras, resistance measurements and by measuring the dimensions of the slurry trails. The method for determining the presence of slurry on the crop was practically applicable and is considered to be reliable. The placement of slurry could not be sufficiently resolved from image taken by the different cameras or by measuring resistance. Instead, visual assessment and measurements of width and depth of the slurry trails gave a good description of the slurry placement in the soil profile. © 2003 Elsevier Science Ltd. All rights reserved.
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| 8. |
- Sundh, I, et al.
(författare)
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Effects of glucose overloading on microbial community structure and biogas production in a laboratory-scale anaerobic digester
- 2003
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Ingår i: Bioresource Technology. - 0960-8524 .- 1873-2976. ; 89:3, s. 237-243
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Tidskriftsartikel (refereegranskat)abstract
- This study characterizes the response of the microbial communities of a laboratory-scale mesophilic biogas process, fed with a synthetic substrate based on cellulose and egg albumin, to single pulses of glucose overloading (15 or 25 times the daily feed based on VS). The microbial biomass and community structure were determined from analyses of membrane phospholipids. The ratio between phospholipid fatty acids (PLFAs; eubacteria and eucaryotes) and di-ethers (PLEL; archaea) suggested that methanogens constituted 4-8% of the microbial biomass. The glucose addition resulted in transient increases in the total biomass of eubacteria while there were only small changes in community structure. The total gas production rate increased, while the relative methane content of the biogas and the alkalinity decreased. However, the biomass of methanogens was not affected by the glucose addition. The results show that the microbial communities of biogas processes can respond quickly to changes in the feeding rate. The glucose overload resulted in a transient general stimulation of degradation rates and almost a doubling of eubacterial biomass, although the biomass increase corresponded to only 7% of the glucose C added. (C) 2003 Elsevier Science Ltd. All rights reserved.
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| 9. |
- Taherzadeh, Mohammad J, 1965-, et al.
(författare)
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Conversion of dilute-acid hydrolyzates of spruce and birch to ethanol by fed-batch fermentation
- 1999
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Ingår i: Bioresource Technology. - Exeter, United Kingdom : Elsevier Sci Ltd. - 0960-8524 .- 1873-2976. ; 69:1, s. 59-66
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Tidskriftsartikel (refereegranskat)abstract
- Fermentation techniques for conversion of dilute acid hydrolyzates were examined. Batch and fed-batch fermentations of hydrolyzates from spruce and birch woods were made in a lab-scale (3.31) anaerobic bioreactor using the yeast Saccharomyces cerevisiae. The spruce and birch hydrolyzates contained high initial concentrations of furfural (2.2 and 5.7 g/l) and 5-hydroxymethylfurfural (HMF, 7.3 and 2.4 g/l), and were found to be strongly inhibiting to the yeast strain used in this study. Fermentation of the hydrolyzates was not possible using a batch mode of operation. However, using a fed-batch technique with a suitably adjusted feed rate, it was found possible to completely ferment the glucose and mannose sugars in both hydrolyzates. Most of the furfural (90%), and part of the HMF (40-70%), present in the hydrolyzates was converted during the fed-batch operation. It is suggested that the success of the fed-batch operation is related to the conversion of furfural and HMF.Fermentation techniques for conversion of dilute acid hydrolyzates were examined. Batch and fed-batch fermentations of hydrolyzates from spruce and birch woods were made in a lab-scale (3.31) anaerobic bioreactor using the yeast Saccharomyces cerevisiae. The spruce and birch hydrolyzates contained high initial concentrations of furfural (2.2 and 5.7 g/l) and 5-hydroxymethylfurfural (HMF, 7.3 and 2.4 g/l), and were found to be strongly inhibiting to the yeast strain used in this study. Fermentation of the hydrolyzates was not possible using a batch mode of operation. However, using a fed-batch technique with a suitably adjusted feed rate, it was found possible to completely ferment the glucose and mannose sugars in both hydrolyzates. Most of the furfural (90%), and part of the HMF (40-70%), present in the hydrolyzates was converted during the fed-batch operation. It is suggested that the success of the fed-batch operation is related to the conversion of furfural and HMF.
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| 10. |
- Taherzadeh, Mohammad J, 1965-, et al.
(författare)
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Production of mycelium biomass and ethanol from paper pulp sulfite liquor by Rhizopus oryzae
- 2003
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Ingår i: Bioresource Technology. - : Elsevier Ltd. - 0960-8524 .- 1873-2976. ; 88:3, s. 167-177
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Tidskriftsartikel (refereegranskat)abstract
- The cultivation conditions for Rhizopus oryzae grown in synthetic medium and paper pulp spent sulfite liquor (SSL) were investigated to achieve high biomass and ethanol yields using shake flasks and bioreactors. The fungus assimilated the hexoses glucose, mannose and galactose, and the pentoses xylose and arabinose as well as acetic acid which are present in SSL. The assimilation of hexoses was faster than pentoses during cultivation in a synthetic medium. However, all sugars were assimilated concomitantly during growth in SSL supplemented with ammonium, magnesium, calcium, phosphate, sulfate and trace amounts of some other metal ions (SSL-S). The medium composition had an important influence on biomass yield. The highest biomass yields, viz. 0.18 and 0.43 g biomass/g sugar were obtained, when the cells were cultivated in shake flasks with a synthetic medium containing glucose as carbon and energy source and SSL-S, respectively. The corresponding yields in a bioreactor with more efficient aeration were 0.22 and 0.55 g/g. In addition to the biomass, ethanol, lactic acid, and glycerol were important extracellular metabolites of the cultivation with maximum yields of 0.37, 0.30 and 0.09 g/g, respectively. When the source of sugars in the medium was exhausted, the fungus consumed the metabolites produced, such that the liquid medium was depleted of potential oxidizable nutrients. In general, there was a direct competition between lactic acid and ethanol among the metabolites. Poor medium compositions and cultivation conditions resulted in higher yields of lactic acid, whereas the ethanol and biomass yields were higher in rich media. SSL-S supported good growth of mycelium and a high ethanol yield.
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