cellulase and xylotriose

In this study, a co-production of two high value-added products, glucose and xylooligosaccharides (XOS), was investigated by utilizing sugarcane bagasse (SB) within a multi-product bio-refinery framework optimized by Box-Behnken design-based response surface methodology. The developed process resulted in a maximum cellulose conversion of xylan-removed SB, 98.69±1.30%, and a maximum extracted SB xylan conversion into XOS (xylobiose and xylotriose) of 57.36±0.79% that was the highest SB xylan conversion reported in the literature, employing cellulase from Penicillium oxalicum EU2106 and recombinant endo-β-1,4-xylanase in Pichia pastoris. Consequently, a mass balance analysis showed that the maximum yields of glucose and XOS were 34.43±0.32g and 5.96±0.09 g per 100 g raw SB. Overall, this described process may be a preferred option for the comprehensive utilization of SB.

Topics: Biotechnology; Cellulase; Cellulose; Disaccharides; Endo-1,4-beta Xylanases; Glucose; Glucuronates; Hydrolysis; Oligosaccharides; Penicillium; Pichia; Saccharum; Trisaccharides

The effects of xylo-oligosaccharides (XOS) and xylose on the hydrolytic activities of cellulases, endoglucanase II (EGII, originating from Thermoascus aurantiacus), cellobiohydrolase I (CBHI, from T. aurantiacus), and cellobiohydrolase II (CBHII, from Trichoderma reesei) on Avicel and nanocellulose were investigated. After the addition of XOS, the amounts of cellobiose, the main product released from Avicel and nanocellulose by CBHI, decreased from 0.78 and 1.37 mg/ml to 0.59 and 1.23 mg/ml, respectively. During hydrolysis by CBHII, the amounts of cellobiose released from the substrates were almost cut in half after the addition of XOS. Kinetic experiments showed that xylobiose and xylotriose were competitive inhibitors of CBHI. The results revealed that the strong inhibition of cellulase by XOS can be attributed to the inhibitory effect of XOS especially on cellobiohydrolase I. The results indicate the necessity to totally hydrolyze xylo-oligosaccharides into the less inhibitory product, xylose, to increasing hydrolytic efficiency.

Topics: Cellulase; Cellulose 1,4-beta-Cellobiosidase; Disaccharides; Enzyme Inhibitors; Glucuronates; Hydrolysis; Kinetics; Oligosaccharides; Thermoascus; Trisaccharides

Commercial cellulase complexes produced by cellulolytic fungi contain enzyme activities that are capable of hydrolyzing non-cellulosic polysaccharides in biomass, primarily hemicellulose and pectins, in addition to cellulose. However, xylanase activities detected in most commercial enzyme preparations have been shown to be insufficient to completely hydrolyze xylan, resulting in high xylooligomer concentrations remaining in the hydrolysis broth. Our recent research showed that these xylooligomers are stronger inhibitors of cellulase activity than others have previously established for glucose and cellobiose, making their removal of great importance. In this study, a HPLC system that can measure xylooligomers with degrees of polymerization (DP) up to 30 was applied to assess how Spezyme CP cellulase, Novozyme 188 β-glucosidase, Multifect xylanase, and non-commercial β-xylosidase enzymes hydrolyze different chain length xylooligomers derived from birchwood xylan. Spezyme CP cellulase and Multifect xylanase partially hydrolyzed high DP xylooligomers to lower DP species and monomeric xylose, while β-xylosidase showed the strongest ability to degrade both high and low DP xylooligomers. However, about 10-30% of the higher DP xylooligomers were difficult to be breakdown by cellulase or xylanase and about 5% of low DP xylooligomers (mainly xylobiose) proved resistant to hydrolysis by cellulase or β-glucosidase, possibly due to low β-xylosidase activity in these enzymes and/or the precipitation of high DP xylooligomers.

Topics: Bacteria; beta-Glucosidase; Betula; Cellulase; Disaccharides; Endo-1,4-beta Xylanases; Glycoside Hydrolases; Hydrolysis; Kinetics; Oligosaccharides; Polymerization; Trisaccharides; Xylose