Title
Induction of highly active β- glucosidase from biomass materials and its application on lignocellulose hydrolysis and fermentation
Authors
LIANG CUIYI XU HUIJUAN ZHANG YU GUO YING CHEN XIAOYAN YUAN ZHENHONG HE MINCHAO and XU JINGLIANG

Received August 13, 2015
Published Volume 51 Issue 7-8 July-August
Keywords β-glucosidase induction, biomass materials, enzyme biocatalysis, bioconversion, ethanol, fermentation

Abstract
To obtain highly active β-glucosidase, low value agricultural residues were used to induce enzyme production. The results showed that rice bran was the best substrate to induce β-glucosidase, likely due to its high magnesium, potassium, and calcium content. The optimum temperature and pH of β-glucosidase were 65 °C and 4.8, respectively. This enzyme was thermo-tolerant and fairly stable, with a long half-life of 15 days at 50 °C. In addition, the enzyme activity was best stimulated in a concentration of 10% (v/v) ethanol. The effects of β-glucosidase on fed-batch hydrolysis of cellulose and high-temperature simultaneous saccharification and fermentation (SSF) were examined. With a cellulase loading of 10 FPU/g of substrate and a β-glucosidase loading of 15 IU/g of substrate, the final substrate loading of 35% dry mass, sugar concentration could attain 225.84 g/L after 120 h of hydrolysis. When the fed-batch SSF process was performed with Kluyveromyces marxianus NCYC 587 operated at 42 °C, after 72 h of fermentation, the maximum ethanol concentration was approximately 49.07 g/L, indicating that β-glucosidase was suitable for lignocellulose conversion into ethanol.