Abstract

In this study, an effort has been made to address the key issue of how molasses quality and composition are key components for higher yields during ethanol fermentation. Moreover, it was also noted that the choice of a yeast strain and yeast preconditioning have a positive effect on alcohol yield during molasses fermentation. A considerably better alcohol yield (9%) was obtained with low residual sugars (< 0.3%), and an increased glycerol concentration from 0.5 to 0.9%. Microbiological analysis revealed a total aerobic count (TAC) of 1.18 × 10⁶ cfu/ml and Lactobacilli count of 8.4 × 10⁵ cfu/ml after 22 h fermentation on de Man, Rogosa and Sharpe (MRS) agar media. The wild yeast count was relatively high reaching 9 × 10² cfu/ml within 40 min of commencement of the fermentation but decreased to 3 × 10⁴ cfu/ml after 22 h of fermentation. This study has shown some of the possible causes of poor fermentation and advantages of cell preconditioning in molasses fermentation by Saccharomyces cerevisiae.

Key words: Ethanol, Saccharomyces cerevisiae, fermentation, molasses,preconditioning.