Comparative Optimization of Ethanol Production Using Immobilized Saccharomyces Cerevisiae and Zymomonas Mobilis

M. Arun Kumar*, S. Sheik Abdullah, K. R. Ramasamy and S. Revathi  

Department of Chemistry and Biosciences, Microbiology Divison, Sastra University Srinivasa Ramanujan Centre Kumbakonam - 612 001 India.

Corresponding Author E-mail: microarun2008@yahoo.in

ABSTRACT: Saccharomyces cerevisiae and Zymomonas mobilis immobilized in calcium alginate beads were used in the continuous production of ethanol. They were grown in medium supplemented with ethanol to screen for a culture, which showed greater than 4% tolerance to ethanol inhibition. Beads were produced from culture slurry containing 2% alginate (w/v), which has added as drops to 2% calcium chloride solution. The immobilized- cell column was operated continuously at steady state for 10 cycles. The yield of ethanol in the immobilized cell system was higher than in free-cell system. To determine their optimum fermentation parameters ethanol production using glucose as a substrate was monitored in continuous systems at varying gel concentrations. Ethanol production rates, as well as residual sugar concentrations were monitored. Rapid fermentation of cane molasses into ethanol has been studied in continuous (free cell and cell- immobilized system). However the removal and discard of used cells remained a problem in the alcoholic fermentations. This obstacle was removed by carefully immobilizing the cells using calcium alginate. Under optimized conditions fermentation was carried out using immobilized cells and good results were obtained. Same immobilized cells after first fermentation were used for next cycle and results were acceptable. The ethanol yield was found to be higher in immobilized Saccharomyces cerevisiae than immobilized Zymomonas mobilis.

KEYWORDS:

Continuous fermentation; sodium alginate; Saccharomyces cerevisiae; Zymomonas mobilis

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