Suspended and immobilized cocultures of the thermotolerant yeast, Klauyveromyces marxianus DMKU 3-1042 and the mesophilic flocculent yeast, Saccharomyces cerevisiae M30 were studied for their abilities to improve production and stability of ethanol fermentation. Sugarcane juice and blackstrap molasses, at initial sugar concentrations of 220 g/L, were used as carbon sources. The results indicated that the coculture system could improve ethanol production from both sugarcane juice and blackstrap molasses when the operating temperature ranged between 33 degrees C and 45 degrees C. High temperature tolerances were achieved when the coculture was immobilized. The immobilized coculture was more effective in high-temperature ethanol fermentation than the suspended cultures. The coculture immobilized on thin-shell silk cocoon and fermented at 37 degrees C and 40 degrees C generated maximal ethanol concentrations of 81.4 and 77.3 g/L, respectively, which were 5.9-8.7% and 16.8-39.0% higher than those of the suspended cultures, respectively. (C) 2012, The Society for Biotechnology, Japan. All rights reserved.