Bioethanol Production from Cassava Peels Inoculated with Saccharomyces cerevisiae and Zymomonas mobilis

Abstract

Aim: This study was designed to determine the bioethanol production from fermented cassava peel using Saccharomyces cerevisiae and Zymomonas mobilis. Methodology: Cassava peels were collected from cassava processing sites, washed, surface sterilized, dried, milled into flour, pretreated, and fermented. Saccharomyces cerevisiae and Z. mobilis suspensions were aseptically inoculated into the fermenting medium and allowed to stand for seven days. The pH, total reducing sugar, chemical composition, and bioethanol composition of the fermenting substrates were determined. Results: A pH decrease from 5.2 to 4.1 was recorded in the sample fermented with S. cerevisiae while the least pH value of 3.8 was obtained from the sample fermented with Z. mobilis, respectively. The total reducing sugar (glucose) of fermented samples decreased from 3.4% to 1.5% (Z. mobilis) and 3.4% to 1.88% (S. cerevisiae) compared with the control sample. The chemical composition showed high protein and fat contents in the fermented samples. High percentage yield of 30% with ethanol volume of 45 mL was recovered from cassava peel inoculated with S. cerevisiae while flash point, i.e. the lowest temperature at which fuel produces enough vapor to cause ignition leading to flame generation of 24oC, was recorded for both fermented samples inoculated with S. cerevisiae and Z. mobilis. Conclusion: The ability of the bacterium and the yeast isolates exhibiting high potential for bioethanol production could be promising in various industrial processes as an alternative to fossil transportation fuel.