Simultaneous saccharification and fermentation of sweet potato powder for the production of ethanol under conditions of very high gravity

Abstract

Due to its merits of drought tolerance and high yield, sweet potatoes are widely considered as a potential alterative feedstock for bioethanol production. Very high gravity (VHG) technology is an effective strategy for improving the efficiency of ethanol fermentation from starch materials. However, this technology has rarely been applied to sweet potatoes because of the high viscosity of their liquid mash. To overcome this problem, cellulase was added to reduce the high viscosity, and the optimal dosage and treatment time were 8 U/g (sweet potato powder) and 1 h, respectively. After pretreatment by cellulase, the viscosity of the VHG sweet potato mash (containing 284.2 g/L of carbohydrates) was reduced by 81%. After liquefaction and simultaneous saccharification and fermentation (SSF), the final ethanol concentration reached 15.5% (v/v), and the total sugar conversion and ethanol yields were 96.5% and 87.8%, respectively.

Key words： bioethanol; sweet potato; very high gravity; viscosity reduction; simultaneous saccharification and fermentation

Acknowledgment

The authors are grateful for the financial support from the National Natural Science Foundation of China (Grant No. 20736006), the National Basic Research Program of China (Grant No. 2007CB714301), the international collaboration project of MOST(2006DFA62400) and Key Projects in the National Science & Technology Pillar Program (No. 2007BAD42B02).

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