Abstract
Backgroundβ-Glucosidase is claimed as a key enzyme in cellulose hydrolysis. The cellulosic fibers are usually entrapped with hemicelluloses containing xylose. So there is ongoing interest in searching for glucose- and xylose-stimulated β-glucosidases to increase the efficiency of hydrolysis of cellulosic biomass.ResultsA thermostable β-glucosidase gene (Bglp) was cloned from Anoxybacillus flavithermus subsp. yunnanensis E13T and characterized. Optimal enzyme activity was observed at 60 °C and pH 7.0. Bglp was relatively stable at 60 °C with a 10-h half-life. The kinetic parameters Vmax and Km for p-nitrophenyl-β-D-glucopyranoside (pNPG) were 771 ± 39 μmol/min/mg and 0.29 ± 0.01 mM, respectively. The activity of Bglp is dramatically stimulated by glucose or xylose at concentrations up to 1.4 M. After Bglp was added to Celluclast® 1.5 L, the conversion of sugarcane bagasse was 48.4 ± 0.8%, which was much higher than of Celluclast® 1.5 L alone. Furthermore, Bglp showed obvious advantages in the hydrolysis when initial concentrations of glucose and xylose are high.ConclusionsThe supplementation of BglP significantly enhanced the glucose yield from sugarcane bagasse, especially in the presence of high concentrations of glucose or xylose. Bglp should be a promising candidate for industrial applications.
Highlights
The production of biofuels from renewable cellulosic biomass is important for the development of alternative energy
The efficient hydrolysis of cellulose requires the synergistic action of endoglucanases, cellobiohydrolases and β-glucosidases (EC 3.2.1.21). β-Glucosidase is responsible for the hydrolysis of oligosaccharides and cellobiose into glucose
Because oligosaccharides and cellobiose act as strong inhibitors of both endoglucanases and cellobiohydrolases, β-glucosidase is considered as a key enzyme for efficient cellulose hydrolysis [1]
Summary
The production of biofuels from renewable cellulosic biomass is important for the development of alternative energy. The efficient hydrolysis of cellulose requires the synergistic action of endoglucanases, cellobiohydrolases and β-glucosidases (EC 3.2.1.21). Β-Glucosidase is responsible for the hydrolysis of oligosaccharides and cellobiose into glucose. Because oligosaccharides and cellobiose act as strong inhibitors of both endoglucanases and cellobiohydrolases, β-glucosidase is considered as a key enzyme for efficient cellulose hydrolysis [1]. Hemicelluloses consist of an available bulk source of xylose. In this context, glucose- and xylose-stimulated βglucosidases appear to be well suited to maximize the overall efficiency of hydrolysis of cellulosic biomass, acting in association with endo- and exocellulases and xylanases [2]. Only a few glucoseand xylose-stimulated β-glucosidases have been characterized [7,8,9].
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