Abstract:
In the present work, studies were carried out on the ethanol production by free and immobilized Saccharomyces cerevisiae GC-IIB31 under stationary culture. Cane molasses in different concentration was used as sugar source for maximum conversion of reducing sugar into ethanol. The substrate was optimized after maintaining different levels of sugar concentrations (12-21%), medium pH (4.0-5.5), incubation temperatures (25-30°C), volume of fermentation medium (200-350 ml) and reuse of immobilized yeast cells. Immobilized yeast cells gave significant results up to four consecutive batches. Rate of ethanol production was maximal with the free cells. The results indicated that 2 g vegetative cells of yeast on utilizing molasses at 15% sugar level with medium pH 4.5 at 30°C and 300 ml fermentation volume in 500ml Erlenmeyer flasks gave maximum ethanol production with both free and immobilized yeast cells. Maximum ethanol production by immobilized yeast cells was obtained in the 4th batch after which it declined markedly. The optimal results are highly significant (p≤0.05, LSD 3.962).
