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Biorefining of wheat straw using an acetic and formic acid based organosolv fractionation process
Snelders, J. ; Dornez, E. ; Benjelloun-Mlayah, B. ; Huijgen, W.J.J. ; Wild, P.J. de; Gosselink, R.J.A. ; Gerritsma, J. ; Courtin, C.M. - \ 2014
Bioresource Technology 156 (2014). - ISSN 0960-8524 - p. 275 - 282.
xylan-degrading enzymes - enzymatic-hydrolysis - lignocellulosic biomass - pretreatment - lignin - fermentation - residues - hemicellulose - bioethanol - cellulose
To assess the potential of acetic and formic acid organosolv fractionation of wheat straw as basis of an integral biorefinery concept, detailed knowledge on yield, composition and purity of the obtained streams is needed. Therefore, the process was performed, all fractions extensively characterized and the mass balance studied. Cellulose pulp yield was 48% of straw dry matter, while it was 21% and 27% for the lignin and hemicellulose-rich fractions. Composition analysis showed that 67% of wheat straw xylan and 96% of lignin were solubilized during the process, resulting in cellulose pulp of 63% purity, containing 93% of wheat straw cellulose. The isolated lignin fraction contained 84% of initial lignin and had a purity of 78%. A good part of wheat straw xylan (58%) ended up in the hemicellulose-rich fraction, half of it as monomeric xylose, together with proteins (44%), minerals (69%) and noticeable amounts of acids used during processing.
Characteristics of Wheat Straw Lignins from Ethanol-based Organosolv Treatment
Huijgen, W.J.J. ; Telysheva, G. ; Arshanitsa, A. ; Gosselink, R.J.A. ; Wild, P.J. de - \ 2014
Industrial Crops and Products 59 (2014). - ISSN 0926-6690 - p. 85 - 95.
industrial applications - enzymatic-hydrolysis - technical lignins - kraft lignin - fractionation - pretreatment - biomass - chemicals - bagasse
Non-purified lignins resulting from ethanol-based organosolv fractionation of wheat straw were characterized for the presence of impurities (carbohydrates and ash), functional groups (hydroxyl, carboxyl and methoxyl), phenyl-propanoid structural moieties, molar mass distribution and thermal behavior. In accordance with its herbaceous nature, the syringyl/guaiacyl-ratio of the wheat straw lignins was substantially lower than of Alcell lignin. In addition, the content of p-hydroxyphenyl and carboxyl groups is substantially higher for the wheat straw lignins. The non-purified organosolv lignins had a high purity with 0.4–5.2% carbohydrate impurities, both originating from lignin to carbohydrate complexes and residual organosolv liquor. The use of H2SO4 in the organosolv process improved the lignin yield, but at low acid doses increased the carbohydrate impurities. For applications where a low amount of carbohydrates is important, lignin from a high-temperature autocatalytic organosolv process was found to be preferred. The highest content of total hydroxyl groups was determined when lignins were produced using 30 mM H2SO4 as catalyst or 50% w/w aqueous ethanol as solvent for the organosolv process. Aliphatic hydroxyl groups, the most predominant type of hydroxyl groups present originating for a substantial part from residual carbohydrates, were found to decrease with reaction time and ethanol proportion of the organosolv solvent. The correlations between organosolv process conditions and lignin characteristics determined can facilitate the use of organosolv lignins in value-added applications such as in polymers and resins and as a feedstock for bio-based aromatics.
Characterization of an acetyl esterase from Myceliophthorathermophila C1 able to deacetylate xanthan
Kool, M.M. ; Schols, H.A. ; Wagenknecht, M. ; Hinz, S.W.A. ; Moerschbacher, B.M. ; Gruppen, H. - \ 2014
Carbohydrate Polymers 111 (2014). - ISSN 0144-8617 - p. 222 - 229.
bacterial polysaccharide xanthan - xylan esterases - carbohydrate esterases - xanthomonas-campestris - rheological properties - plant polysaccharides - enzymatic-hydrolysis - gum - transition - families
Screening of eight carbohydrate acetyl esterases for their activity towards xanthan resulted in the recogni-tion of one active esterase. AXE3, a CAZy family CE1 acetyl xylan esterase originating from Myceliophthorathermophila C1, removed 31% of all acetyl groups present in xanthan after a 48 h incubation. AXE3 activ-ity towards xanthan was only observed when xanthan molecules were in the disordered conformation.Optimal performance towards xanthan was observed at 53¿C in the complete absence of salt, a condi-tion favouring the disordered conformation. AXE3-deacetylated xanthan was hydrolyzed using cellulasesand analyzed for its repeating units using UPLC–HILIC–ELSD/ESI–MS. This showed that AXE3 specificallyremoves the acetyl groups positioned on the inner mannose and that acetyl groups positioned on theouter mannose are not removed at all. After a prolonged incubation at optimal conditions, 57% of allacetyl groups, representing 70% of all acetyl groups on the inner mannose units, were hydrolyzed.
Characterization of Phosphorus in Animal Manures Collected from Three (Dairy, Swine, and Broiler) Farms in China
Li, G. ; Li, H. ; Leffelaar, P.A. ; Shen, J. ; Zhang, F. - \ 2014
PLoS ONE 9 (2014)7. - ISSN 1932-6203
magnetic-resonance-spectroscopy - enzymatic-hydrolysis - organic phosphorus - northwest germany - poultry litter - forms - soil - diets - speciation - fractions
In order to identify the phosphorus species and concentration in animal manure, we comparatively characterized phosphorus in dairy manure, swine manure, and broiler litter, using a sequential procedure, a simplified two-step procedure (NaHCO3/NaOH+EDTA), and a solution Phosphorus-31 Nuclear Magnetic Resonance (31P-NMR) spectroscopy procedure. In the sequential procedure, deionized water extracted 39, 22, and 32%; NaHCO3 extracted 48, 26, and 37%; NaOH extracted 8, 9, and 13.8%; and HCl extracted 3, 42.8, and 17% of the total phosphorus in dairy manure, swine manure and broiler litter, respectively. Total phosphorus extracted by the NaHCO3/NaOH+EDTA procedure was 7.5, 32.4, and 15.8 g P kg-1 for dairy manure, swine manure, and broiler litter, respectively. The solution 31P-NMR procedure detected that 9, 34, and 29% of total phosphorus was phytic acid in dairy manure, swine manure, and broiler litter, respectively. These results show that phosphorus forms, availability, and quantities differ between animal manures, which provides valuable information for P characterization of animal manures in China.
The influence of amylose-LPC complex formation on the susceptibility of wheat starch to amylase
Ahmadi-Abhari, S. ; Woortman, A.J.J. ; Oudhuis, A.A.C.M. ; Hamer, R.J. ; Loos, K. - \ 2013
Carbohydrate Polymers 97 (2013)2. - ISSN 0144-8617 - p. 436 - 440.
slow digestion property - native cereal starches - lipid complexes - enzymatic-hydrolysis - rice starch - in-vivo - digestibility - oligosaccharide - glucose - systems
This study was aimed to assess the role of lysophosphatidylcholine (LPC) in the development of slowly digestible starch (SDS). The influence of LPC, on the enzymatic degradation of diluted 9% wheat starch suspensions (w/w) was investigated, using an in vitro digestion method. Wheat starch suspensions containing 0.5–5% LPC (based on starch) were heated in a Rapid Visco Analyser (RVA) till 95 °C and subjected to enzyme hydrolysis by porcine pancreatic a-amylase at 37 °C for several digestion periods. In vitro digestion measurements demonstrated that complexing starch with 5% LPC leads to a 22% decrease in rate of reducing sugar compared to the reference while the samples containing 0.5% LPC showed an equal digestibility comparable to the control. A clear decrease in the formation of reducing sugars was observed in presence of 2–5% LPC, since the results after 15 min digestion imply the formation of SDS due to the formation of amylose-LPC inclusion complexes. The DSC measurements proved the presence of amylose-LPC inclusion complexes even after 240 min digestion demonstrating the low susceptibility of amylose-V complexes to amylase.
Performance of hemicellulolytic enzymes in culture supernatants from a wide range of fungi on insoluble wheat straw and corn fiber fractions
Gool, M.P. van; Toth, K. ; Schols, H.A. ; Szakacs, G. ; Gruppen, H. - \ 2012
Bioresource Technology 114 (2012). - ISSN 0960-8524 - p. 523 - 528.
xylan-degrading enzymes - enzymatic-hydrolysis - aspergillus-awamori - pretreatment - cellulose - arabinoxylans - fermentation - degradation - adsorption - substrate
Filamentous fungi are a good source of hemicellulolytic enzymes for biomass degradation. Enzyme preparations were obtained as culture supernatants from 78 fungal isolates grown on wheat straw as carbon source. These enzyme preparations were utilized in the hydrolysis of insoluble wheat straw and corn fiber xylan rich fractions. Up to 14% of the carbohydrates in wheat straw and 34% of those in corn fiber were hydrolyzed. The degree of hydrolysis by the enzymes depended on the origin of the fungal isolate and on the complexity of the substrate to be degraded. Penicillium, Trichoderma or Aspergillus species, and some non-identified fungi proved to be the best producers of hemicellulolytic enzymes for degradation of xylan rich materials. This study proves that the choice for an enzyme preparation to efficiently degrade a natural xylan rich substrate, is dependent on the xylan characteristics and could not be estimated by using model substrates.
In vitro pH-Stat protein hydrolysis of feed ingredients for Atlantic cod, Gadus morhua. 2. In vitro protein digestibility of common and alternative feed ingredients
Tibbetts, S. ; Verreth, J.A.J. ; Lall, S.P. - \ 2011
Aquaculture 319 (2011)3-4. - ISSN 0044-8486 - p. 407 - 416.
melanogrammus-aeglefinus l - salmon salmo-salar - apparent digestibility - rainbow-trout - juvenile haddock - nonstarch polysaccharide - gastrointestinal model - nutrient digestibility - enzymatic-hydrolysis - incorporation level
Using enzyme fractions isolated from the pyloric caeca of farmed Atlantic cod, the in vitro degree of protein hydrolysis (DH) of numerous conventional and novel feed ingredients were measured by a closed-system pH-Stat assay. Regression equations describing the relationship between in vivo apparent protein digestibility (ADC) and in vitro protein DH were used to predict in vitro protein ADC. The equations resulted in good correlation (
Hydrolysis of ß-casein by the cell-envelope-located PI-type protease of Lactococcus lactis: A modelling approach
Munoz-Tamayo, R. ; Groot, J. de; Bakx, E.J. ; Wierenga, P.A. ; Gruppen, H. ; Zwietering, M.H. ; Sijtsma, L. - \ 2011
International Dairy Journal 21 (2011)10. - ISSN 0958-6946 - p. 755 - 762.
acid bacteria - kappa-casein - streptococcus-cremoris - enzymatic-hydrolysis - milk - kinetics - proteolysis - strains - peptide - system
Lactic acid bacteria possess extracellular proteases that hydrolyze milk proteins. This work aimed to describe mathematically the hydrolysis of intact ß-casein by the PI-type protease of Lactococcus lactis, using a mutant strain that lacks the oligopeptide transport system. Experiments were performed under a broad range of initial protein concentrations (17–196 µm), at constant enzyme concentration or at constant initial enzyme/substrate ratio. Hydrolysis of the intact ß-casein was monitored and quantified. Four kinetic functions were evaluated to describe the hydrolysis: First-order, nth-order, Michaelis–Menten, and competitive inhibition kinetics. The hydrolysis rate was found to depend on the initial protein concentration, due to the micellisation behaviour of ß-casein. This effect was accounted for by modifying the kinetic functions. The modified competitive inhibition model provided the lowest mean square error. This model has only three parameters and described the hydrolysis of intact ß-casein effectively for a broad range of initial conditions.
Effect of neutrase, alcalase, and papain hydrolysis of whey protein concentrates on iron uptake by Caco-2 cells
Ou, K.Q. ; Liu, Y.Z. ; Zhang, L.B. ; Yang, X.G. ; Huang, Z.W. ; Nout, M.J.R. ; Liang, J. - \ 2010
Journal of Agricultural and Food Chemistry 58 (2010)8. - ISSN 0021-8561 - p. 4894 - 4900.
in-vitro digestion - enzymatic-hydrolysis - culture model - phytic acid - milk - peptides - availability - bioavailability - dialyzability - solubility
Effects of enzymatic hydrolysates of whey protein concentrates (WPC) on iron absorption were studied using in vitro digestion combined with Caco-2 cell models for improved iron absorption. Neutrase- and papain-treated WPC could improve iron absorption; especially hydrolysates by Neutrase could significantly increase iron absorption to 12.8% compared to 3.8% in the control. Hydrolysates by alcalase had negative effects to the lowest at 0.57%. Two new bands at molecular weights (MW) around and below 10 kDa occurred at tricine-SDS-PAGE of hydrolysates by Neutrase, and one new band at MW below 10 kDa occurred in hydrolysates by papain. No new band was observed in hydrolysates by alcalase. Concentration of free amino acids indicated that, except for tyrosine and phenylalanine, amino acids in papain-treated hydrolysates were higher than that of alcalase, and no cysteine and proline were found in hydrolysates by alcalase. The results suggested that hydrolysate by Neutrase-treated WPC is a promising facilitator for iron absorption. Peptides of MW around and lower than 10 kDa and aspartic acid, serine, glutamic acid, glycin, cysteine, histidine, and proline may be contributors to enhancement
Optimization of the dilute maleic acid pretreatment of wheat straw
Kootstra, A.M.J. ; Beeftink, H.H. ; Scott, E.L. ; Sanders, J.P.M. - \ 2009
Biotechnology for Biofuels 2 (2009). - ISSN 1754-6834 - p. 31 - 31.
cellulose hydrolysis - enzymatic-hydrolysis - ethanologenic yeast - high-temperature - organic-acids - corn stover - pig diets - d-xylose - biomass - degradation
Background - In this study, the dilute maleic acid pretreatment of wheat straw is optimized, using pretreatment time, temperature and maleic acid concentration as design variables. A central composite design was applied to the experimental set up. The response factors used in this study are: (1) glucose benefits from improved enzymatic digestibility of wheat straw solids; (2) xylose benefits from the solubilization of xylan to the liquid phase during the pretreatment; (3) maleic acid replenishment costs; (4) neutralization costs of pretreated material; (5) costs due to furfural production; and (6) heating costs of the input materials. For each response factor, experimental data were fitted mathematically. After data translation to €/Mg dry straw, determining the relative contribution of each response factor, an economic optimization was calculated within the limits of the design variables. Results - When costs are disregarded, an almost complete glucan conversion to glucose can be reached (90% from solids, 7%-10% in liquid), after enzymatic hydrolysis. During the pretreatment, up to 90% of all xylan is converted to monomeric xylose. Taking cost factors into account, the optimal process conditions are: 50 min at 170°C, with 46 mM maleic acid, resulting in a yield of 65 €/Mg (megagram = metric ton) dry straw, consisting of 68 €/Mg glucose benefits (from solids: 85% of all glucan), 17 €/Mg xylose benefits (from liquid: 80% of all xylan), 17 €/Mg maleic acid costs, 2.0 €/Mg heating costs and 0.68 €/Mg NaOH costs. In all but the most severe of the studied conditions, furfural formation was so limited that associated costs are considered negligible. Conclusions - After the dilute maleic acid pretreatment and subsequent enzymatic hydrolysis, almost complete conversion of wheat straw glucan and xylan is possible. Taking maleic acid replenishment, heating, neutralization and furfural formation into account, the optimum in the dilute maleic acid pretreatment of wheat straw in this study is 65 €/Mg dry feedstock. This is reached when process conditions are: 50 min at 170°C, with a maleic acid concentration of 46 mM. Maleic acid replenishment is the most important of the studied cost factors
Effects of thermo-chemical pre-treatment on anaerobic biodegradability and hydrolysis of lignocellulosic biomass
Fernandes, T. ; Klaasse Bos, G.J. ; Zeeman, G. ; Sanders, J.P.M. ; Lier, J.B. van - \ 2009
Bioresource Technology 100 (2009)9. - ISSN 0960-8524 - p. 2575 - 2579.
corn stover - enzymatic-hydrolysis - wheat-straw - technologies - switchgrass - manure - acid
The effects of different thermo-chemical pre-treatment methods were determined on the biodegradability and hydrolysis rate of lignocellulosic biomass. Three plant species, hay, straw and bracken were thermo-chemically pre-treated with calcium hydroxide, ammonium carbonate and maleic acid. After pre-treatment, the plant material was anaerobically digested in batch bottles under mesophilic conditions for 40 days. From the pre-treatment and subsequent anaerobic digestion experiments, it was concluded that when the lignin content of the plant material is high, thermo-chemical pre-treatments have a positive effect on the biodegradability of the substrate. Calcium hydroxide pre-treatment improves the biodegradability of lignocellulosic biomass, especially for high lignin content substrates, like bracken. Maleic acid generates the highest percentage of dissolved COD during pre-treatment. Ammonium pre-treatment only showed a clear effect on biodegradability for straw.
Pressure-Aided Proteolysis of ß-Casein
Bruins, M.E. ; Creusot, N.P. ; Gruppen, H. ; Janssen, A.E.M. ; Boom, R.M. - \ 2009
Journal of Agricultural and Food Chemistry 57 (2009)12. - ISSN 0021-8561 - p. 5529 - 5534.
high hydrostatic-pressure - lactoglobulin-b - enzymatic-hydrolysis - milk-proteins - whey proteins - chymotrypsin - association - peptides - trypsin - immunoreactivity
ß-Casein, which is present in the form of micelles at atmospheric pressure, has been hydrolyzed during pressure treatment to improve the accessibility of the protein. Two proteolytic enzymes with different specificities were used. Trypsin was aimed at mainly hydrolyzing hydrophilic segments of ß-casein and chymotrypsin at hydrolyzing hydrophobic segments of ß-casein. Measurements on aggregation during hydrolysis at atmospheric pressure showed that probably not micelle disruption, but disruption of much larger aggregates, occurs in the process. Peptide profiles were measured via reversed-phase chromatography. Measurements on enzyme activity after pressure treatments showed that trypsin was inactivated by pressure, which could explain all differences in peptide profiles compared to atmospheric experiments. Pressure did not influence the reaction mechanism, probably because the hydrophilic part of ß-casein is sufficiently accessible. However, chymotryptic proteolysis under pressure yielded new peptides that could not be explained by a change in enzyme activity. Here, pressure altered the mechanism of hydrolysis, by changing either enzyme specificity or substrate accessibility, which led to different peptides that can have different properties
Modelling ethanol production from cellulose: separate hydrolysis and fermentation versus simultaneous saccharification and fermentation
Drissen, R.E.T. ; Maas, R.H.W. ; Tramper, J. ; Beeftink, H.H. - \ 2009
Biocatalysis and Biotransformation 27 (2009)1. - ISSN 1024-2422 - p. 27 - 35.
enzymatic-hydrolysis - lignocellulose - biomass - conversion - softwood - technology - inhibition - substrate - economics
In ethanol production from cellulose, enzymatic hydrolysis, and fermentative conversion may be performed sequentially (separate hydrolysis and fermentation, SHF) or in a single reaction vessel (simultaneous saccharification and fermentation, SSF). Opting for either is essentially a trade-off between optimal temperatures and inhibitory glucose concentrations on the one hand (SHF) vs. sub-optimal temperatures and ethanol-inhibited cellulolysis on the other (SSF). Although the impact of ethanol on cellobiose hydrolysis was found to be negligible, formation of glucose and cellobiose from cellulose were found to be significantly inhibited by ethanol. A previous model for the kinetics of enzymatic cellulose hydrolysis was, therefore, extended with enzyme inhibition by ethanol, thus allowing a rational evaluation of SSF and SHF. The model predicted SSF processing to be superior. The superiority of SSF over SHF (separate hydrolysis and fermentation) was confirmed experimentally, both with respect to ethanol yield on glucose (0.41 g g-1 for SSF vs. 0.35 g g-1 for SHF) and ethanol production rate, being 30% higher for an SSF type process. High conversion rates were found to be difficult to achieve since at a conversion rate of 52% in a SSF process the reaction rate dropped to 5% of its initial value. The model, extended with the impact of ethanol on the cellulase complex proved to predict reaction progress accurately.
Pretreatments to enhance the digestibility of lignocellulosic biomass
Hendriks, A.T.W.M. ; Zeeman, G. - \ 2009
Bioresource Technology 100 (2009)1. - ISSN 0960-8524 - p. 10 - 18.
steam-explosion pretreatment - wet oxidation pretreatment - ethanol-tolerant mutant - yellow-poplar sawdust - liquid hot-water - enzymatic-hydrolysis - clostridium-thermocellum - wheat-straw - corn stover - lime pretreatment
Lignocellulosic biomass represents a rather unused source for biogas and ethanol production. Many factors, like lignin content, crystallinity of cellulose, and particle size, limit the digestibility of the hemicellulose and cellulose present in the lignocellulosic biomass. Pretreatments have as a goal to improve the digestibility of the lignocellulosic biomass. Each pretreatment has its own effect(s) on the cellulose, hemicellulose and lignin; the three main components of lignocellulosic biomass. This paper reviews the different effect(s) of several pretreatments on the three main parts of the lignocellulosic biomass to improve its digestibility. Steam pretreatment, lime pretreatment, liquid hot water pretreatments and ammonia based pretreatments are concluded to be pretreatments with high potentials. The main effects are dissolving hemicellulose and alteration of lignin structure, providing an improved accessibility of the cellulose for hydrolytic enzymes.
Differential effects of mineral and organic acids on the kinetics of arabinose degradation under lignocellulose pretreatment conditions
Kootstra, A.M.J. ; Mosier, N.S. ; Scott, E.L. ; Beeftink, H.H. ; Sanders, J.P.M. - \ 2009
Biochemical Engineering Journal 43 (2009)1. - ISSN 1369-703X - p. 92 - 97.
saccharomyces-cerevisiae - high-temperature - fumaric-acid - cellulose hydrolysis - enzymatic-hydrolysis - rhizopus-oryzae - corn stover - pig diets - d-xylose - ethanol
Sugar degradation occurs during acid-catalyzed pretreatment of lignocellulosic biomass at elevated temperatures, resulting in degradation products that inhibit microbial fermentation in the ethanol production process. Arabinose, the second most abundant pentose in grasses like corn stover and wheat straw, degrades into furfural. This paper focuses on the first-order rate constants of arabinose (5 g/L) degradation to furfural at 150 and 170 °C in the presence of sulfuric, fumaric, and maleic acid and water alone. The calculated degradation rate constants (kd) showed a correlation with the acid dissociation constant (pKa), meaning that the stronger the acid, the higher the arabinose degradation rate. However, de-ionized water alone showed a catalytic power exceeding that of 50 mM fumaric acid and equaling that of 50 mM maleic acid. This cannot be explained by specific acid catalysis and the shift in pKw of water at elevated temperatures. These results suggest application of maleic and fumaric acid in the pretreatment of lignocellulosic plant biomass may be preferred over sulfuric acid. Lastly, the degradation rate constants found in this study suggest that arabinose is somewhat more stable than its stereoisomer xylose under the tested conditions
Hydrolysis of Brewers' Spent Grain by Carbohydrate Degrading Enzymes
Forssell, P. ; Kontkanen, H. ; Schols, H.A. ; Hinz, S.W.A. ; Eijsink, V.G.H. ; Treimo, J. ; Robertson, J.A. ; Waldron, K.W. ; Faulds, C.B. ; Buchert, J. - \ 2008
Journal of the Institute of Brewing 114 (2008)4. - ISSN 0046-9750 - p. 306 - 314.
enzymatic-hydrolysis - ferulic acid - baking properties - cereal products - cell-walls - barley - release - fiber - oligosaccharides - solubilization
In this work four commercial cellulase-hemicellulase mixtures with different activity profiles were used for solubilization of carbohydrates from brewers' spent grain (BSG). After the enzyme treatment, both the solubilised fraction and the unhydrolysed residue were characterized. Treatment with 5,000 nkat/g xylanase for 5 h at 50 degrees C resulted in the solubilisation of 13-14% of the BSG dry weight as monosaccharides. This corresponded to the solubilisation of 26-28% of the original carbohydrates and 30-34% of original arabinoxylans, depending on the enzyme cocktail used. The relatively low hydrolysis level indicates that the majority of the BSG biomass is rather recalcitrant towards the cellulose-hemicellulase enzyme mixtures applied in this study. The enzyme activity profile had a crucial impact on the chemistry of the oligosaccharides produced through the solubilisation of BSG. The presence of feruloyl esterase (FAE) activity in the enzyme cocktail resulted in the production of free ferulic acid, arabinoxylo-oligosaccharides and their corresponding monomers. However, when the enzyme mixture was devoid of FAE activity, ferulic acid was still bound to the oligosaccharides. The unhydrolysed fraction was still found to contain over 40% of carbohydrates after enzymatic treatment despite the extensive enzyme dosages used. The protein fraction remained largely unaffected (i.e. insoluble) by the carbohydrate-disrupting enzyme treatments. In addition to the recalcitrant carbohydrates, the residue was enriched with lignin and lipid type structures.
Pilot-scale conversion of lime-treated wheat straw into bioethanol: quality assessment of bioethanol and valorization of side streams by anaerobic digestion and combustion
Maas, R.H.W. ; Bakker, R.R.C. ; Boersma, A.R. ; Bisschops, I. ; Pels, J.R. ; Jong, E. de; Weusthuis, R.A. ; Reith, H. - \ 2008
Biotechnology for Biofuels 1 (2008). - ISSN 1754-6834
ethanol-production - lignocellulosic materials - saccharomyces-cerevisiae - enzymatic-hydrolysis - biomass - pretreatment - fermentation - acid - saccharification - softwood
The limited availability of fossil fuel sources, worldwide rising energy demands and anticipated climate changes attributed to an increase of greenhouse gasses are important driving forces for finding alternative energy sources. One approach to meeting the increasing energy demands and reduction of greenhouse gas emissions is by large-scale substitution of petrochemically derived transport fuels by the use of carbon dioxide-neutral biofuels, such as ethanol derived from lignocellulosic material. Results This paper describes an integrated pilot-scale process where lime-treated wheat straw with a high dry-matter content (around 35% by weight) is converted to ethanol via simultaneous saccharification and fermentation by commercial hydrolytic enzymes and bakers' yeast (Saccharomyces cerevisiae). After 53 hours of incubation, an ethanol concentration of 21.4 g/liter was detected, corresponding to a 48% glucan-to-ethanol conversion of the theoretical maximum. The xylan fraction remained mostly in the soluble oligomeric form (52%) in the fermentation broth, probably due to the inability of this yeast to convert pentoses. A preliminary assessment of the distilled ethanol quality showed that it meets transportation ethanol fuel specifications. The distillation residue, which contained non-hydrolysable and non-fermentable (in)organic compounds, was divided into a liquid and solid fraction. The liquid fraction served as substrate for the production of biogas (methane), whereas the solid fraction functioned as fuel for thermal conversion (combustion), yielding thermal energy, which can be used for heat and power generation. Conclusion Based on the achieved experimental values, 16.7 kg of pretreated wheat straw could be converted to 1.7 kg of ethanol, 1.1 kg of methane, 4.1 kg of carbon dioxide, around 3.4 kg of compost and 6.6 kg of lignin-rich residue. The higher heating value of the lignin-rich residue was 13.4 MJ thermal energy per kilogram (dry basis).
Improving the corn-ethanol industry: studying protein separation techniques to obtain higher value added product options for distillers grains
Brehmer, B. ; Bals, B. ; Sanders, J.P.M. ; Dale, B. - \ 2008
Biotechnology and Bioengineering 101 (2008)1. - ISSN 0006-3592 - p. 49 - 61.
enzymatic-hydrolysis - pretreatment - biomass - energy - stover
Currently in America the biofuel ethanol is primarily being produced by the dry grind technique to obtain the starch contained in the corn grains and subsequently subjected to fermentation. This so-called 1st generation technology has two setbacks; first the lingering debate whether its life cycle contributes to a reduction of fossil fuels and the animal feed sectors future supply/demand imbalance caused by the co-product dry distillers grains (DDGS). Additional utilization of the cellulosic components and separation of the proteins for use as chemical precursors have the potential to alleviate both setbacks. Several different corn feedstock layouts were treated with 2nd generation ammonia fiber expansion (AFEX) pre-treatment technology and tested for protein separation options (protease solubilization). The resulting system has the potential to greatly improve ethanol yields with lower bioprocessing energy costs and satisfy a significant portion of the organic chemical industry.
A stochastic model for predicting dextrose equivalent and saccharide composition during hydrolysis of starch by alpha-amylase
Besselink, T. ; Baks, T. ; Janssen, A.E.M. ; Boom, R.M. - \ 2008
Biotechnology and Bioengineering 100 (2008)4. - ISSN 0006-3592 - p. 684 - 697.
monte-carlo-simulation - bacillus-licheniformis - enzymatic-hydrolysis - soluble starch - kinetic-model - potato starch - amylopectin - amylolysis - enzymes - thermostability
A stochastic model was developed that was used to describe the formation and breakdown of all saccharides involved during -amylolytic starch hydrolysis in time. This model is based on the subsite maps found in literature for Bacillus amyloliquefaciens -amylase (BAA) and Bacillus licheniformis -amylase (BLA). Carbohydrate substrates were modeled in a relatively simple two-dimensional matrix. The predicted weight fractions of carbohydrates ranging from glucose to heptasaccharides and the predicted dextrose equivalent showed the same trend and order of magnitude as the corresponding experimental values. However, the absolute values were not the same. In case a well-defined substrate such as maltohexaose was used, comparable differences between the experimental and simulated data were observed indicating that the substrate model for starch does not cause these deviations. After changing the subsite map of BLA and the ratio between the time required for a productive and a non-productive attack for BAA, a better agreement between the model data and the experimental data was observed. Although the model input should be improved for more accurate predictions, the model can already be used to gain knowledge about the concentrations of all carbohydrates during hydrolysis with an -amylase. In addition, this model also seems to be applicable to other depolymerase-based systems
Effect of gelatinization and hydrolysis conditions on the selectivity of starch hydrolysis with alpha-amylase from Bacillus licheniformis
Baks, T. ; Bruins, M.E. ; Matser, A.M. ; Janssen, A.E.M. ; Boom, R.M. - \ 2008
Journal of Agricultural and Food Chemistry 56 (2008)2. - ISSN 0021-8561 - p. 488 - 495.
high hydrostatic-pressure - wheat-starch - enzymatic-hydrolysis - phase-transformations - temperature - mechanism - enzymes - stability - complexes - products
Enzymatic hydrolysis of starch can be used to obtain various valuable hydrolyzates with different compositions. The effects of starch pretreatment, enzyme addition point, and hydrolysis conditions on the hydrolyzate composition and reaction rate during wheat starch hydrolysis with ¿-amylase from Bacillus licheniformis were compared. Suspensions of native starch or starch gelatinized at different conditions either with or without enzyme were hydrolyzed. During hydrolysis, the oligosaccharide concentration, the dextrose equivalent, and the enzyme activity were determined. We found that the hydrolyzate composition was affected by the type of starch pretreatment and the enzyme addition point but that it was just minimally affected by the pressure applied during hydrolysis, as long as gelatinization was complete. The differences between hydrolysis of thermally gelatinized, high-pressure gelatinized, and native starch were explained by considering the granule structure and the specific surface area of the granules. These results show that the hydrolyzate composition can be influenced by choosing different process sequences and conditions.
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