A family 12 endoglucanase with a molecular mass of 23,926 Da (EG-II) from the brown-rot basidiomycete Fomitopsis palustris was purified and characterized. One of the roles of EG-II in wood ...degradation is thought to be to loosen the polysaccharide network in cell walls by disentangling hemicelluloses that are associated with cellulose.
Utilization of
d-xylose as carbon source for production of bacterial cellulose was studied. Seventeen strains of acetic acid bacteria were screened for their cellulose productivity in
d-glucose,
...d-xylose, and
d-xylose/
d-xylulose mixed media, respectively.
d-Xylose was not well metabolized by any bacterial strains that exhibited high cellulose production in
d-glucose medium. Consequently, bacterial cellulose production in
d-xylose medium was unsuccessful.
d-Xylose, however, became utilizable substrate for bacterial strains if xylose-isomerase was added to the medium.
Acetobacter xylinus IFO 15606 was the best cellulose producer in
d-xylose/
d-xylulose mixed medium, so cultural conditions were studied for enhanced cellulose production. With pH controlled, the strain could produce cellulose at a yield exceeding 0.3
g per 100
ml of
d-xylose/
d-xylulose mixed medium, which was comparable to the yields in
d-glucose medium by excellent producers in the literature.
Two types of substrates, the algal-bacterial type (rich in cellulose I
α) cellulose and the cotton-ramie type (dominant in cellulose I
β) cellulose, were degraded comparatively by
Trichoderma viride ...cellulase. The algal-bacterial type cellulose microfibril was more susceptible than the cotton-ramie type. The residual cellulose microfibrils were observed by TEM and analyzed by FTIR and electron diffraction. It becomes clear that the residual cellulose of the algal-bacterial type cellulose was getting rich in the cellulose I
β with the lapse time of cellulase treatment. These results indicate that the cellulose I
α in the microfibril of the algal-bacterial type cellulose is hydrolyzed preferentially by the cellulase.
The objective of this study was to characterize the decay of acetylated wood due to brown-rot and white-rot fungi by analysis of chemical composition, X-ray measurements, and13C-NMR spectroscopy. The ...decay by brown-rot fungus became inhibited at a weight percent gain (WPG) due to acetylation of more than 10%, and the mass loss (LOSS) due to decay became zero at a WPG of about 20%. The LOSS due to white-rot fungus decreased slowly with the increase in WPG, reaching zero at a WPG of about 12%. The losses of lignin by brown-rot decay increased initially with the decrease in LOSS owing to the progressing acetylation and then decreased at a LOSS of less than 60%. Polysaccharides were more easily decomposed than lignin during the decay of acetylated wood due to brown-rot fungus. The losses of both components due to white-rot decay decreased as the LOSS decreased with progressing acetylation. The white-rot fungus tended to preferentially decompose the lignin during the decay of acetylated wood. The brown-rot fungus decomposed the cellulose in the crystalline region to a large degree when the LOSS was more than 40%, whereas the white-rot fungus decomposed the crystalline region and the noncrystalline region in acetylated wood to the same degree. The brown-rot fungus preferentially decomposed unsubstituted xylose units in acetylated wood and partly decomposed the mono-substituted xylose units. It was suggested that the mono- and disubstituted cellulose were partly decomposed by brown-rot fungus.
This paper reports an attempt to characterize the residues extracted after enzymatic hydrolysis of
Cladophora microcrystalline cellulose comprising two crystalline allomorphs of cellulose, Iα and I
...β. Cellulose I
α is preferentially hydrolyzed by
Trichoderma cellulase (
Hayashi, Ishihara, Sugiyama, & Okano, 1998a). This selective hydrolysis process produced short elements. X-ray diffraction, electron diffraction and FT-IR analyses revealed that these short elements were highly crystalline, similar to the untreated microcrystalline cellulose, and mostly consisted of the I
β phase. The length distribution of the crystalline elements was ca. 350
nm. Furthermore, the average length of 350
nm corresponded to the degree of polymerization of 690 for β-glucan chains obtained by size exclusion chromatographic analysis. The close agreement indicates that individual molecular chains may be extended in the longitudinal direction of the obtained crystalline element. These characteristic short elements have the potential to act as nano-ordered particles and may be useful as fillers to enhance the mechanical properties of various materials.
To investigate the bleaching mechanism, a lignincarbohydrate complex (LCC) model compound, a vinyl ether-type lignin model dimer, and a hexeneuronic acid model compound were treated with dilute ...sulfuric acid of different pHs. Beech kraft pulp and red pine kraft pulp were also treated with dilute sulfuric acid and then extracted with aqueous alkali. The amount of hexeneuronic acid degradation products in acid effluents and lignin dissolved in alkali effluents were determined. It was found that the benzyl ether-type LCC bond and the vinyl ether bond in lignin were effectively cleaved under the pH where sulfuric acid bleaching of kraft pulp was effective. Hexeneuronic acid group was also effectively degraded during sulfuric acid bleaching. In beech kraft pulp bleaching, both lignin removal and hexeneuronic acid removal contributed to the kappa number reduction. In red pine bleaching, the contribution of hexeneuronic acid removal was negligible, and most of the kappa number reduction was achieved by the lignin removal.
Lignocelluloses (steamed hardwood and hardwood kraft pulp) were semicontinuously hydrolyzed on a large scale 2-2.5 kg of substrate vs. 20,000 IU filter paperase (FPase) using a 10-L hydrolysis ...reactor with an ultrafiltration unit for the recovery and reuse of cellulases. The substrate was added to the reactor at appropriate intervals to keep a concentration of approximately 5% (w/v). All of the enzyme was added at the beginning and no further addition was done. The ultrafiltration unit was operated intermittently rather than continuously due to its enough capacity (dilution rate of 2.5 h(-1)) and making the enzyme durable. The enzyme required to produce one gram of reducing sugar in this reactor was 273 FPase IU/g RS for steamed hardwood and 7.4 FPase IU/g RS for hardwood kraft pulp. The sugar composition of hydrolyzate was unaltered virtually from beginning to end of the hydrolysis in spite of the progressive loss of enzyme activities. The analysis of the enzyme composition in the hydrolyzate during hydrolysis revealed that an exo-beta-D-glucanase component was adsorbed selectively at the stages of advanced hydrolysis extent.
We previously reported that the algal-bacterial type cellulose microfibril was more susceptible to enzymatic attack than the cotton-ramie type cellulose. In cellulose crystallite (CC) of the ...algal-bacterial type cellulose, the cellulose I
α crystal component was more selectively degraded than the cellulose I
β crystal component. The shortened CC was observed frequently in the residue of
Cladophora CC. Fibrillation was observed in the residual
Halocynthia CC and repeatedly hydrolyzed
Cladophora CC that richly contained cellulose I
β. These results may suggest the supermolecular structure of CCs.
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