INDUCTION OF HIGHLY ACTIVE beta-GLUCOSIDASE FROM BIOMASS MATERIALS AND ITS APPLICATION ON LIGNOCELLULOSE HYDROLYSIS AND FERMENTATION

To obtain highly active beta-glucosidase, low value agricultural residues were used to induce enzyme production. The results showed that rice bran was the best substrate to induce beta-glucosidase, likely due to its high magnesium, potassium, and calcium content. The optimum temperature and pH of beta-glucosidase were 65 degrees C and 4.8, respectively. This enzyme was thermo-tolerant and fairly stable, with a long half-life of 15 days at 50 degrees C. In addition, the enzyme activity was best stimulated in a concentration of 10% (v/v) ethanol. The effects of beta-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 beta-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 degrees C, after 72 h of fermentation, the maximum ethanol concentration was approximately 49.07 g/L, indicating that beta-glucosidase was suitable for lignocellulose conversion into ethanol.