Ethanol production from dilute-acid pretreated rice straw by simultaneous saccharification and fermentation with Mucor indicus, Rhizopus oryzae, and Saccharomyces cerevisiae

Karimi, K.; Emtiazi, G.; Taherzadeh, M.J.

Enzyme and Microbial Technology 40(1): 138-144

2006


ISSN/ISBN: 0141-0229
DOI: 10.1016/j.enzmictec.2005.10.046
Accession: 012053186

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Abstract
Ethanol production from rice straw by simultaneous saccharification and fermentation (SSF) with Mucor indicus, Rhizopus oryzae, and Saccharomyces cerevisiae was investigated and compared with pure cellulose, Avicel, as a reference. The straw was pretreated with dilute-acid hydrolysis. The SSF experiments were carried out aerobically and anaerobically at 38 degrees C, 50 g/l dry matter (DM) solid substrate concentration and 15 or 30 filter paper unit (FPU)/g DM of a commercial cellulase. The experiments were ended after 7 days, while an average of 2-3 days were usually enough to achieve the maximum ethanol yield. All the strains were able to produce ethanol from the pretreated rice straw with an overall yield of 40-74% of the maximum theoretical SSF yield, based on the glucan available in the solid substrate. R. oryzae had the best ethanol yield as 74% from rice straw followed by M. indicus with an overall yield of 68% with 15 FPU/g DM of cellulase. Glycerol was the main byproduct of the SSF by M. indicus and S. cerevisiae with yields 117 and 90 mg/g of equivalent glucose in the pretreated straw, respectively, while R. oryzae produced lactic acid as the major byproduct with yield 60 mg/g glucose equivalent in pretreated rice straw under anaerobic conditions.