Simultaneous saccharification and fermentation of rice straw into ethanol.

The physicochemical pretreatment of ball milled rice straw with different oxidizing agents, peracetic acid, alkali-peroxide, manganese-peroxide compounds under steaming pressure were studied. The pretreatment resulted in major changes in chemical composition of rice straw. The peroxide treated substrates were found to be most susceptible to enzymatic saccharification. A maximum saccharification (77.4%) of alkaline-peroxide treated rice straw (5%, w/v) was achieved using cellulase enzyme produced by mixed cultivation of Trichoderma reesei Rut C-30 and Aspergillus ochraceus containing 1.83 FPU, 1.63 cellobiase and xylanase 2.03 IU/ml. The hydrolysate was fermented using coculture of a temperature resistant strain of Saccharomyces cerevisiae and Pachysolen tannophilus resulting in 1.5% (w/v) ethanol. The SSF of 10.0% (w/v) H2O2-MnSO4 treated straw yielded maximum ethanol (2.9%, w/v) after 72 h at 40 degrees C. As a consequence of the well-balanced cellulase production by mixed fungal culture, the supplementation of cellobiase or xylanase was not necessary in the simultaneous saccharification and fermentation process.