Herein an ethanol production process from rice straw was optimized. Simultaneous saccharification and co-fermentation (SSCF) using Saccharomyces cerevisiae and Scheffersomyces stipitis co-culture was carried out to enhance ethanol production. The optimal saccharification solid loading was 5%. Key fermentation parameters for co-culture including cell ratio, agitation rate and temperature was rationally optimized using design of experiment (DoE). Optimized co-culture conditions for maximum ethanol production efficiency were at S. cerevisiae:S. stipitis cell ratio of 0.31, agitation rate of 116 rpm and temperature of 33.1 degrees C. The optimized SSCF process reached ethanol titer of 15.2 g/L and ethanol yield of 99% of theoretical yield, consistent with the DoE model prediction. Moreover, SSCF process under high biomass concentration resulted in high ethanol concentration of 28.6 g/L. This work suggests the efficiency and scalability of the developed SSCF process which could provide an important basis for the economic feasibility of ethanol production from lignocelluloses. (C) 2013 Elsevier Ltd. All rights reserved.