Bioconversion of starch to ethanol in a single-step process by coculture of amylolytic yeasts and Saccharomyces cerevisiae 21

Ethanol production by a coculture of Saccharomyces diastaticus and Saccharo myces cerevisiae 21 was 24.8 g/l using raw unhydrolysed starch in a single- step fermentation. This was 48% higher than the yield obtained with the mon oculture of S. diastaticus (16.8 g/l). The maximum ethanol fermentation eff iciency was achieved (93% of the theoretical value) using 60 g/l starch con centration. In another coculture fermentation with E. capsularis and S. cer evisiae 21, maximum ethanol yield was 16.0 g/l, higher than the yield with the monoculture of Endomycopsis capsularis. In batch fermentations using co cultures maximum ethanol production occurred in 48 h of fermentation at 30 degrees C using 60 g/l starch. Fermentation efficiency was found lower in a two-step process using sr-amylase and glucoamylase-treated starch. (C) 199 9 Elsevier Science Ltd. All rights reserved.