Simultaneous saccharification and fermentation of acid-pretreated corncobs with a recombinant Saccharomyces cerevisiae expressing β-glucosidase

Author

• Yu Shen^a, b, 
• Yan Zhang^a, 
• Tao Ma^a, 
• Xiaoming Bao^a, , , , 
• Fengguang Du^b, 
• Guoqiang Zhuang^a, 
• Yinbo Qu^a

• ^a State Key Laboratory of Microbial Technology, Shandong University, Jinan 250100, PR China
• ^b Tianguan Distillery Company, Nanyang 473000, PR China

Received 2 July 2007, Revised 20 September 2007, Accepted 20 September 2007, Available online 31 October 2007

Abstract

To reduce the cellobiose inhibition of exoglucanase and endogulcanase and enhance cellulose hydrolysis during simultaneous saccharification and fermentation (SSF), a β-glucosidase encoding gene named BGL1 was cloned from Saccharomycopsis fibuligera and integrated into the chromosomal rDNA region of the Saccharomyces cerevisiae industrial strain NAN-27 producing NAN-227. Compared with the parental strain, which had no detectable activity, the β-glucosidase specific activity in NAN-227 was 1.02 IU/mg of protein. When cellobiose was used as the sole carbon source in a shake-flask, NAN-227 consumed 6.2 g/L of cellobiose and produced 3.3 g/L of ethanol in 48 h. The yield was 0.532 g/g. The parent strain only consumed 1.92 g/L of cellobiose and no ethanol was detected. During the SSF of acid-pretreated corncobs NAN-227 produced 20 g/L of ethanol at 72 h, which was similar to the parent strain when 20 IU of β-glucosidase/g of substrate was added.

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