In this work, Trichoderma reesei Aq-5b and Trichoderma viride NSW-XM, capable of excreting lignin-degrading enzymes and cellulase were used to create a mixed culture system to hydrolyze rice straw in situ. The results showed that Aq-5b and NSW-XM were able to co-grow and produce complementary lignin degrading enzymes, namely laccase and lignin peroxidase. The two microorganisms were able to produce 22.74 g/L of reducing sugar in the optimal condition. For fermentation of the hydrolysates produced, Saccharomyces cerevisiae and Candida tropicalis NSW-NW were co-immobilized in polymer beads composed of sodium alginate, polyvinyl alcohol, and silicon dioxide (SA-PVA-SiO2). The beads remained intact after 4 cycles of use and provided satisfactory protection for the yeasts and a suitable microenvironment for ethanol fermentation, greatly improved the efficiency of ethanol production, shortened the fermentation cycle and achieved yeasts recycling for continuous or batch-fed fermentation. The productivity of ethanol reached up to 2.17 g/(L h).
Bibliographical noteFunding Information:
The authors are grateful for financial support of the Research Program of Sate Key Laboratory of Food Science and Technology, Nanchang University , China (Grant Nos. SKLF-QN-201517 and SKLF-ZZB-201312 ), of the Natural Science Foundation of China ( 21266022 ), of the National High-tech R&D Program of China ( 2012AA101809 ), of the International Science & Technology Cooperation Program of China (Grant No. 2014DFA61040 ), and of the Science and Technology Project of Jiangxi Provincial Department of Science and Technology (Grant Nos. KJLD 12011 & 2013AFC30044 ).
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- Enzymatic hydrolysis in-situ
- Lignin-degrading enzymes
- Mixed culture
- Rice straw