Solka Floc Research Articles

Cloning, expression and characterization of a family-74 xyloglucanase from Thermobifida fusca.

Thermobifida fusca xyloglucan-specific endo-beta-1,4-glucanase (Xeg)74 and the Xeg74 catalytic domain (CD) were cloned, expressed in Escherichia coli, purified and characterized. This enzyme has a glycohydrolase family-74 CD that is a specific xyloglucanase followed by a family-2 carbohydrate binding module at the C terminus. The Michaelis constant (Km) and maximal rate (Vmax) values for hydrolysis of tamarind seed xyloglucan (tamXG) are 2.4 micro m and 966 micro mol xyloglucan oligosaccharides (XGOs) min-1. micro mol protein-1. More than 75% of the activity was retained after a 16-h incubation at temperatures up to 60 degrees C. The enzyme was most active at pH 6.0-9.4. NMR analysis showed that its catalytic mechanism is inverting. The oligosaccharide products from hydrolysis of tamXG were determined by MS analysis. Cel9B, an active carboxymethylcellulose (CMC)ase from T. fusca, was also found to have activity on xyloglucan (XG) at 49 micro mol.min-1. micro mol protein-1, but it could not hydrolyze XG units containing galactose. An XG/cellulose composite was prepared by growing Gluconacetobacterxylinus on glucose with tamXG in the medium. Although a mixture of purified cellulases was unable to degrade this material, the composite material was fully hydrolyzed when Xeg74 was added. T. fusca was not able to grow on tamXG, but Xeg74 was found in the culture supernatant at the same level as was found in cultures grown on Solka Floc. The function of this enzyme appears to be to break down the XG surrounding cellulose fibrils found in biomass so that T. fusca can utilize the cellulose as a carbon source.

Evaluation of transgenic event Bt11 hybrid corn in broiler chickens

A feeding study evaluated whether standard broiler diets prepared with grain derived from Syngenta Seeds NK Brand Bacillus thuringiensis (Bt) Corn hybrids had any adverse effects on male or female broiler chickens. Four kinds of corn grain were used in this study: (1) grain from the Bt-expressing field corn hybrid N7070Bt, (2) grain from the N7070Bt hybrid that had been sprayed with Liberty brand herbicide (glufosinate) according to manufacturer's instructions (N7070Bt + Liberty), (3) grain from standard N7070 (non-Bt isoline of N707OBt) grain, and (4) a lot of North Carolina grown grain from the 2000 growing season (NC2000). The amino acid balance for the four lots of corn was similar relative to their crude protein content; however, the NC2000 corn had higher protein content. Diets with the higher protein NC2000 season corn were amended with a combination of sand, ground cardboard (Solka Floc), and poultry fat so that the metabolizable energy and crude protein content of the diluted diets would be similar to that of the isoline and transgenic diets. Growth of broilers was excellent with males being significantly heavier than females (2,497 g vs. 2,103 g) at 42 d of age. BW of live birds at 42 d was within 26 g for the three treatment groups fed corn that was from the same genetic background, i.e., the two Bt transgenic groups (N7070Bt, N7070Bt + Liberty), and the non-Bt N7070 isoline corn group, while BW for the NC2000 group was significantly lower by 93 g. There was no overall corn source effect on feed conversion ratio (FCR) among the isoline and transgenic corn sources to 42 d of age, but FCR was poorer for broilers consuming the commercial NC2000 corn. There was no overall effect of corn source on survivability to 42 d. Carcass analysis at 48 d demonstrated no differences in percentage carcass yield due to corn source among males and females. The transgenic N7070Bt and N7070Bt + Liberty hybrid diets supported excellent broiler chicken growth with mortality and FCR that were similar to that supported by the N7070 isoline control and better than rates from the commercial NC2000 corn without significant differences among treatment groups in carcass yield. It was clear that the transgenic corn had no deleterious or unintended effects on production traits of broiler chickens in this study.

Effect of particle sizes on functional properties of dietary fibre prepared from sugarcane bagasse

Alkaline hydrogen peroxide (AHP) treatment affected physical and chemical properties of sugarcane bagasse (SB). AHP treatment can improve all its physical properties. The brightness, water-holding capacity (WHC), and oil-binding capacity (OBC) of SB were increased by 34, 96, and 55%, respectively. Lignin was removed from SB by 53%. Colour of Solka Floc® 900, a commercial dietary fibre, was pure white (L=93.51); WHC and OBC were 8.61 g water/g sample and 7.34 g oil/g sample, respectively. The results showed a highly positive correlation between particle size reduction of each dietary fibre (DF), WHC and OBC. While density showed a negative correlation, densities of AHP-SB and Solka Floc® 900 were increased, with particle size reduction, from 1.06 to 1.34 and from 1.09 to 1.28, respectively. At 5% of AHP-SB and Solka Floc® 900 substitution in bread, reductions of loaf volume and softness of bread were observed in direct opposition to particle size reduction. The most acceptable breads contained 5% of AHP-SB and Solka Floc® 900 when the particle sizes were <0.075 and <0.106 mm, respectively.

Effect of particle sizes on in-vitro calcium and magnesium binding capacity of prepared dietary fibers

Microscopic examination showed a change on the surface structure of dietary fibers (DF) from rice straw (RS) and sugarcane bagasse (SB) by alkaline hydrogen peroxide (AHP) treatment. Effect of particle size on in-vitro binding of calcium (Ca) and magnesium (Mg) of AHP-RS, AHP-SB and Solka Floc® 900 (SF) were evaluated. Total bound Ca and Mg decreased with particle size reduction ( P<0.05) for all types of DF. Ca and Mg (82–95%) were released from AHP-RS and AHP-SB by acid washing but only 53–60% Mg was removed from SF. There were strong correlations between water holding capacity, oil binding capacity and particle density and total bound Ca and Mg for all DF samples.

Comparative evaluations of powder and mechanical properties of low crystallinity celluloses, microcrystalline celluloses, and powdered celluloses

The purpose of this study was to examine and compare the powder and mechanical properties of different batches of low crystallinity powdered cellulose (LCPC-S1 to LCPC-S5) with those of commercial microcrystalline celluloses (MCC) (Avicel PH-101, Avicel PH-102, Avicel PH-103, Avicel PH-301, Avicel PH-302, and Emcocel 90m) and powdered celluloses (PC) (Solka Floc BW-40 and Solka Floc BW-100). Both the LCPC and MCC products were aggregated powders, whereas, the PC materials showed a fibrous structure. The primary particles forming the LCPC aggregates, however, were smaller in size and showed a greater degree of coalescence between boundaries, than those forming the MCC aggregates. The LCPC materials had significantly higher bulk and tap densities and lower porosity values compared with the MCC materials. The yield pressure value calculated from the linear region of the Heckel curve for LCPC varied between 48 and 70 MPa, for Avicel and PC materials between, 80 and 106 MPa, and for Emcocel 90m was 48 MPa. These results suggest that the LCPC products and Emcocel 90m, compared with commercial MCC and PC excipients, undergo plastic deformation at relatively lower compression pressures. The total volume reduction (i.e. compressibility), determined by calculating the area under the Heckel curve (AUHC), however, was comparable for all materials, with the exception of the LCPC-S3, which owing to the low yield pressure value, showed the largest reduction in volume. With the exception of LCPC-S1 and Solka Floc BW-40, all the other materials formed compacts, whose strength ranged from about 522 to 799 MPa 2. The strengths of LCPC-S1 and Solka Floc BW-40 compacts, in contrast, were 214 and 257 MPa 2, respectively. Irrespective of the solid fraction levels, the LCPC compacts, in general, disintegrated much faster than the MCC and PC compacts. In conclusion, the results suggest that the new LCPC materials reported herein have powder properties that are quite different from the MCC and PC materials evaluated, and show clear potential as direct compression excipients.

Synthesis and regulation of D-xylanase from Cellulomonas flavigena wild type and a mutant

The xylanolytic system from Cellulomonas flavigena was enhanced by adding cellulose to the growth medium. The Solka floc:xylan (60:40 w/w) mixture induced xylanase synthesis by more than 3-fold over that induced by growing C. flavigena, wild type and its mutant PN-120 on pure xylan. The hydrolysis pattern of sugar cane bagasse and xylan indicated the presence of debranching endo-β;-xylanase activity.

Cellulase production on bagasse pretreated with hot water.

Because pretreatment of biomass with hot water only in differential flow systems offers very digestible cellulose and potentially less inhibition by liquid hydrolysate, solids and liquid hydrolysate from bagasse pretreated with hot water were fed to a batch cellulase production system using the Rut C30 strain of Trichoderma reesei to determine the suitability of these substrates for cellulase production. The organism was found to be sensitive to inhibitors in the liquid hydrolysate but could be adapted to improve its tolerance. In addition, filtering of the material reduced inhibitory effects. The organism was also sensitive to some component in the solids, and they had to be washed heavily to achieve good growth and cellulase production rates. Even then, a lag was found before enzyme production would commence on pretreated solids whereas no such lag was experienced with Solka Floc. However, once enzyme production began, as high and even somewhat greater cellulase productivities were realized with washed pretreated solids. Adding lignin to Solka Floc delayed enzyme production, suggesting that lignin or other materials in the lignin solids could cause the lag observed for pretreated bagasse, but more studies are needed to resolve the actual reason for this delay.

ACEII, a Novel Transcriptional Activator Involved in Regulation of Cellulase and Xylanase Genes of Trichoderma reesei

A novel yeast-based method to isolate transcriptional activators was applied to clone regulators binding to the cellulase promoter cbh1 of the filamentous fungus Trichoderma reesei (Hypocrea jecorina). This led to the isolation of the cellulase activator ace2 encoding for a protein belonging to the class of zinc binuclear cluster proteins found exclusively in fungi. The DNA-binding domain of ACEII was expressed as a glutathione S-transferase fusion protein in Escherichia coli, and ACEII was shown to bind in vitro to the 5'-GGCTAATAA site present in the cbh1 promoter. This site also contains the proposed binding sequence of the xylanase activator XlnR of Aspergillus niger. Mutation of the GGC triplet abolished ACEII binding. The function of ACEII was studied by analyzing the effects of ace2 deletion in the hypercellulolytic T. reesei strain ALKO2221. Deletion of the ace2 gene led to lowered induction kinetics of mRNAs encoding the major cellulases cellobiohydrolases I and II and endoglucanases I and II and to 30-70% reduced cellulase activity when the fungus was grown on medium containing Solka floc cellulose. The expression level of the gene encoding xylanase was also affected. ace2 deletion led to lowered xyn2 expression in cellulose-induced cultivation. Cellulase induction by sophorose was not affected by ace2 deletion.

Simultaneous saccharification and fermentation of lignocellulosic wastes to ethanol using a thermotolerant yeast

Simultaneous saccharification and fermentation (SSF) studies were carried out to produce ethanol from lignocellulosic wastes (sugar cane leaves and Antigonum leptopus leaves) using Trichoderma reesei cellulase and yeast cells. The ability of a thermotolerant yeast, Kluyveromyces fragilis NCIM 3358, was compared with Saccharomyces cerevisiae NRRL-Y-132. K. fragilis was found to perform better in the SSF process and result in high yields of ethanol (2.5–3.5% w/v) compared to S. cerevisiae (2.0–2.5% w/v). Increased ethanol yields were obtained when the cellulase was supplemented with β-glucosidase. The conversions with K. fragilis were completed in a short time. The substrates were in the following order in terms of fast conversions: Solka floc > A. leptopus > sugar cane.

Fruit and vegetable fiber fermentation by gut microflora from canines.

The objective of this study was to assess fermentability by canine gut microflora to include shortchain fatty acid (SCFA) production, organic matter (OM) disappearance, and gas production of vegetable and fruit fiber sources compared to fiber standards (psyllium, citrus pectin, and Solka Floc). Fiber sources included apple pomace, carrot pomace, flaxseed, fruit blend (mixture of peach, almond, nectarine, and plum), grape pomace, pea hulls, pistachio, and tomato pomace. Substrates were fermented in vitro for 4, 12, and 24 h with fecal flora obtained from three healthy dogs. Citrus pectin had the highest OM disappearance, SCFA production, and gas production at all times of fermentation; psyllium was intermediate and Solka Floc was lowest. A wide variation in fermentability was noted among the vegetable and fruit fiber sources. Apple pomace, carrot pomace, and flaxseed had the greatest fermentability as assessed by OM disappearance. Pea hulls and tomato pomace had intermediate OM disappearances, and fruit blend, grape pomace, and pistachio were poorly fermented. Carrot pomace produced the largest amounts of gas and SCFA. Apple pomace produced high concentrations of gas but intermediate concentrations of SCFA. Pea hulls and tomato pomace produced intermediate concentrations of gas and SCFA, whereas flaxseed, fruit blend, grape pomace, and pistachio produced low amounts of these fermentation products. For all substrates collectively, OM disappearance was highly correlated with both gas production (r2 = 0.782 and 0.723 for 12- and 24-h values, respectively) and SCFA production (r2 = 0.737 and 0.738 for 12- and 24-h values, respectively). In general, OM disappearance, gas production, and SCFA production were related to the insoluble:soluble fiber ratio in the samples; as the insoluble:soluble ratio decreased (increased soluble fiber), the OM disappearance, gas production, and SCFA production increased.

Characterisation of xylanases produced in liquid and compost cultures of the cultivated mushroom Agaricus bisporus

The production and properties of Agaricus bisporus endoxylanase and β-xylosidase were studied in compost and liquid cultures. A. bisporus was grown on minimal medium with solka floc BW40, oat spelt xylan, Whatman CC41 microcrystalline cellulose, D-xylose and D-glucose as carbon sources. Endoxylanase activity and β-xylosidase activity were found during growth with complex carbon sources such as cellulose or xylan and no activity was present with sugars such as glucose or xylose. In compost culture endoxylanase activity increased during and after the button stage of fruit body development and decreased after fruit body harvest. The production of β-xylosidase differed in that it was only detectable during the button stage of development. Using activity staining and preparative IEF, three endoxylanase activities were separated from liquid cultures and three principal endoxylanase activities were separated from compost extract. The pH optima and IEF profiles of these activities were similar. Only one β-xylosidase activity was found in liquid culture, whereas two were found in compost culture; the IEF profiles of the compost activities differed markedly from those of the β-xylosidase found in liquid culture.

Simultaneous production of high activities of thermostable endoglucanase and beta-glucosidase by the wild thermophilic fungus Thermoascus aurantiacus.

The culture-medium composition was optimised, on a shake-flask scale, for simultaneous production of high activities of endoglucanase and beta-glucosidase by Thermoascus aurantiacus using statistical factorial designs. The optimised medium containing 40.2 g l(-1) Solka Floc as the carbon source and 9 g l(-1) soymeal as the organic nitrogen source yielded 1130 nkat ml(-1) endoglucanase and 116 nkat ml(-1) beta-glucosidase activities after 264 h as shake cultures. In addition, good levels of beta-xylanase (3479 nkat ml(-1)) and low levels of filter-paper cellulase, beta-xylosidase, alpha-L-arabinofuranosidase, beta-mannanase, beta-mannosidase, alpha-galactosidase and beta-galactosidase were detected. Batch fermentation in a 5-1 laboratory fermentor using the optimised medium allowed the production of 940 nkat ml(-1) endoglucanase and 102 nkat ml(-1) beta-glucosidase in 192 h. Endoglucanase and beta-glucosidase showed optimum activity at pH 4.5 and pH 5, respectively, and they displayed optimum activity at 75 degrees C. Endoglucanase and beta-glucosidase showed good stability at pH values 4-8 and 4-7, respectively, after a prolonged incubation (48 h at 50 degrees C). Endoglucanase had half-lives of 98 h at 70 degrees C and 4.1 h at 75 degrees C, while beta-glucosidase had half-lives of 23.5 h at 70 degrees C and 1.7 h at 75 degrees C. Alkali-treated bagasse, steam-treated wheat straw, Solka floc and Sigmacell 50 were 66, 48.5, 33.5 and 14.4% hydrolysed by a crude enzyme complex of T. aurantiacus in 50 h.

Simultaneous saccharification and extractive fermentation of cellulosic substrates

Alcohol fermentation has traditionally been carried out in aqueous environments because of the ready solubility of reactant (sugar) and product (ethanol). However, extraction of the product ethanol into a nonmiscible phase can result in kinetic benefits due to reduced inhibition of the fermentation reactions. In this study, we report the development of a novel simultaneous saccharification and extractive fermentation (SSEF) process. Ethanol productivity was increased by up to 65% over conventional (nonextractive) fed-batch simultaneous saccharification systems when calculated on the basis of aqueous phase volume. The amount of water required for SSEF reactions was dramatically reduced from that required for conventional SSF. In batch SSEF reactors with 2.5% aqueous phase, 50% conversion of 25% (aqueous phase concentration) Solka Floc could be achieved in 48 h using 2 FPU/g cellulase.

Responses of IsaBrown laying hens to a pre-layer diet containing additional calcium and to dietary protein and lysine concentrations during lay

IsaBrown pullets were obtained from a commercial breeder at 15 (Expt 1) and 16 (Expt 2) weeks of age and housed in either single-bird or multiple 5-bird cages in a high rise, windowless layer house in which temperatures were maintained below 30˚C by computerised control of fans and evaporative cooling pads. In Expt 1, they were fed either a grower diet or a pre-layer diet consisting of the grower diet containing additional calcium to 18 weeks of age and then maintained during lay to 56 weeks of age on diets containing either 160 or 180 g crude protein (CP)/kg. In Expt 2, they were fed the grower diet to 19 weeks of age and then 1 of 5 diets similar in all ingredients except that the lysine concentration varied between 7.35 and 8.95 g/kg in increments of 0.4 g/kg. The L-lysine HCl supplements were added in lieu of solka floc, an inert cellulose supplement. In Expt 1, mortality was low (2.25%), peak egg production was high (95–98%), and the mean rate of lay at 56 weeks of age was above 88%. The diet fed prior to lay had no significant effect on production during lay. Feed intake and egg production were similar for hens fed both dietary protein levels during lay, and egg weight and egg mass output were greater for hens fed the diet containing 180 g CP/kg. Hens in multiple-bird cages ate significantlyless feed for a significantly smaller daily egg mass output. In Expt 2, increasing the dietary lysine concentration significantly reduced feed intake and significantly increased lysine intake, egg shell breaking strength, and albumen height. Multiple-caged hens had a significantly lower hen-housed egg production as a result of a 7-fold increase in mortality compared with hens in single cages, due mainly to cannibalism. The daily lysine requirement formaximum egg production approximated 940 mg for hens in single cages and 975 mg for hens in multiple-bird cages.

Cellulase production of Trichoderma reesei Rut C 30 using steam-pretreated spruce. Hydrolytic potential of cellulases on different substrates.

Various techniques are available for the conversion of lignocellulosics to fuel ethanol. During the last decade processes based on enzymatic hydrolysis of cellulose have been investigated more extensively, showing good yield on both hardwood and softwood. The cellulase production of a filamentous fungi, Trichoderma reesei Rut C 30, was examined on carbon sources obtained after steam pretreatment of spruce. These materials were washed fibrous steam-pretreated spruce (SPS), and hemicellulose hydrolysate. The hemicellulose hydrolysate contained, besides water-soluble carbohydrates, lignin and sugar degradation products, which were formed during the pretreatment and proved to be inhibitory to microorganisms. Experiments were performed in a 4-L laboratory fermentor. The hydrolytic capacity of the produced enzyme solutions was compared with two commercially available enzyme preparations, Celluclast and Iogen Cellulase, on SPS, washed SPS, and Solka Floc cellulose powder. There was no significant difference among the different enzymes produced by T. reesei Rut C 30. However, the conversion of cellulose using these enzymes was higher than that obtained with Iogen or Celluclast cellulases using steam-pretreated spruce as substrate.

Editorial

IsaBrown pullets were obtained from a commercial breeder at 15 (Expt 1) and 16 (Expt 2) weeks of age and housed in either single-bird or multiple 5-bird cages in a high rise, windowless layer house in which temperatures were maintained below 30˚C by computerised control of fans and evaporative cooling pads. In Expt 1, they were fed either a grower diet or a pre-layer diet consisting of the grower diet containing additional calcium to 18 weeks of age and then maintained during lay to 56 weeks of age on diets containing either 160 or 180 g crude protein (CP)/kg. In Expt 2, they were fed the grower diet to 19 weeks of age and then 1 of 5 diets similar in all ingredients except that the lysine concentration varied between 7.35 and 8.95 g/kg in increments of 0.4 g/kg. The L-lysine HCl supplements were added in lieu of solka floc, an inert cellulose supplement. In Expt 1, mortality was low (2.25%), peak egg production was high (95–98%), and the mean rate of lay at 56 weeks of age was above 88%. The diet fed prior to lay had no significant effect on production during lay. Feed intake and egg production were similar for hens fed both dietary protein levels during lay, and egg weight and egg mass output were greater for hens fed the diet containing 180 g CP/kg. Hens in multiple-bird cages ate significantlyless feed for a significantly smaller daily egg mass output. In Expt 2, increasing the dietary lysine concentration significantly reduced feed intake and significantly increased lysine intake, egg shell breaking strength, and albumen height. Multiple-caged hens had a significantly lower hen-housed egg production as a result of a 7-fold increase in mortality compared with hens in single cages, due mainly to cannibalism. The daily lysine requirement formaximum egg production approximated 940 mg for hens in single cages and 975 mg for hens in multiple-bird cages.

Steroid metabolism along the gastrointestinal tract of the cannulated pig

Steroid metabolism along the gastrointestinal tract of the cannulated pig was studied. Thi was achieved by fitting simple gut cannulas in the terminal ileum, caecum and mid-colon of three Landrace x large white boars, which enabled convenient collection of digesta and faecal samples at defined time points. Biochemical analyses showed that the neutral steroid profile of the pig is similar to that of man, dominated by cholesterol and its bacterial metabolite coprostanol. In contrast, pigs consuming a normal diet excrete appreciably lower quantities of neutral sterols in faeces. The major primary bile acids detected were the glycine and taurine amidates of hyocholic and chenodeoxycholic acids, which were rapidly converted to the free bile acids and subsequently dehydroxylated to hyodeoxycholic and lithocholic acids respectively, in the terminal ileum and caecum. Bacterial deconjugation and 7 alpha-dehyrdoxylation are virtually complete in the caecum with negligible further metabolism in the colon and faeces. On a wet weight basis the concentration of both neutral and acid steroids was shown to increase aborally. Inclusion of dietary fibre in the form of cellulose (Solka floc) and guar gum reduced steroid concentration considerably at all sites of the large intestine, which is consistent with their stool bulking effects. In conclusion, this study shows that intestinal steroid metabolism in the pig is similar to that in man despite slightly different bile acid profiles and, therefore, the multicannulated pig may serve as a useful model of man in chemoprevention studies of colorectal cancer.

In situ neutral detergent insoluble nitrogen as a method for measuring forage protein degradability.

A method of estimating the undegraded intake protein (UIP) concentration of forages was developed and validated with a series of in situ experiments. The hypothesis was that UIP calculated from in situ neutral detergent insoluble N (NDIN) is equal to total in situ N minus the microbial N that is estimated from purines (MN). The in situ disappearance rates of total in situ N (TN), MN, and NDIN were measured for six hay samples and two range masticate samples. Hypothetical rates of passage (2 or 5%/h) were used to calculate UIP (% of DM) for each N pool. Estimates of UIP from TN were higher (P = .0001) than those from either MN or NDIN, and MN estimates of UIP were similar (P = .48) to NDIN estimates. A low-N fiber source (solka floc) was incubated in situ for 8 h. Analysis of the residue detected purines before, but not after, neutral detergent extraction. Several in situ incubation (i.e., Dacron bag size and number of Dacron bags in a mesh bag) and neutral detergent extraction conditions were tested. None of the factors tested affected in situ NDIN disappearance (P > .05). The hypothesis that NDIN is completely digestible in the rumen was tested. Estimates of the extent of NDIN digestion were made using 96-h in situ incubations, and UIP was recalculated for the test samples. Mean in situ UIP concentration decreased upon recalculation (P = .05). In situ NDIN provides estimates of forage UIP that are equal to estimates from MN. Forage UIP estimates are less when extent of N degradation is estimated and included in the calculation.

Effect of compressional force on the crystallinity of directly compressible cellulose excipients

The effect of compressional force on the crystallinity of low crystallinity cellulose (LCPC), microcrystalline celluloses (Avicel ® PH-101, PH-102 and PH-302 grades) and powdered cellulose (Solka Floc BW-100) has been investigated using an X-ray diffraction method. Microcrystalline and powdered celluloses showed an increase of about 10% in their crystallinities, compared to the values for the corresponding powders, at a compression pressure of 5–10 MPa. The increase in the crystallinity of LCPC was gradual and reached the maximum value of 5% at a compression pressure of 15 MPa. Further increase in compression pressure (to 77 MPa) had no effect on the crystallinity of LCPC, Avicel ® PH-101, Avicel ® PH-302 and Solka Floc BW-100. Avicel ® PH-102, on the other hand, showed a decrease in crystallinity at 15 MPa. Beyond 15 MPa, however, no statistically significant change in the crystallinity of the product was noted.

Use of hemicellulose hydrolysate for β-glucosidase fermentation

Hydrolysis of cellulose by Trichoderma cellulases often results in a mixture of glucose, cellobiose, and low-mol-wt cellodextrins. Cellobiose is nonfermentable for most yeasts, and therefore it has to be hydrolyzed to glucose by beta-glucosidase prior to ethanol fermentation. In the present study, the beta-glucosidase production of one Penicillium and three Aspergillus strains, which were previously selected out of 24 strains, was investigated on steam pretreated willow. Both steam-pretreated willow and hemicellulose hydrolysate, released during steam explosion of willow, were used as carbon sources. Reference cultivation runs were performed using prehydrolyzed Solka Floc and glucose. The four strains were compared with Trichoderma reesei regarding sugar consumption and beta-glucosidase production. Aspergillus niger and Aspergillus phoenicis proved to be the best enzyme producers on hemicellulose hydrolysate. The maximum beta-glucosidase activity, 4.60 IU/mL, was obtained when A. phoenicis was cultivated on the mixture of hemicellulose hydrolysate and steam-pretreated willow. The maximum yield of enzyme activity, 502 IU/g total carbohydrate, was obtained when Aspergillus foetidus was cultivated on the hemicellulose hydrolysate.