Simultaneous Saccharification and Fermentation of Corn Cobs to Bio-ethanol by Co-culture of Aspergillus Niger and Saccharomyces Cerevisiae

Abstract

The production of bio-ethanol from corn is a mature technology that is not likely to see significant reduction in the production costs. Substantial cost reductions may be possible if cellulose based agricultural wastes such as corn cobs are used instead of corn. In this study, corn cobs which are in abundance and do not interfere with food security was subjected to simultaneous saccharification and fermentation process by co-culture of Aspergillus niger and Saccharomyces cerevisiae for 7 days. The corn cobs were sundried, milled into powder using hammer milling and stored at room temperature (25OC) before use. The growth media used for culturing Aspergilus niger and Saccharomyces cerevisiae inocula were prepared respectively. Parameters such as biomass yield, cell dry weight, reducing sugar concentration, pH of the fermentation medium and the ethanol yield were determined at 24 hours intervals. The results of the study revealed that the yeast and mould biomass yield obtained from the corn cobs on the 7th day was 0.59 (OD), while the microbial cell dry weight obtained on the same day was 0.88mg/cm3. The substrate was hydrolyzed to produce 0.63mg/cm3 reducing sugar concentrations. The pH values of the fermentation medium varied between 3.05 and 7.58. Optimal ethanol yield of 10.08v/v was obtained after 7 days of fermentation. The results of this study suggest that agricultural wastes that contain fermentable sugars can no longer be discarded into our environment, but should be converted to useful products like bio-ethanol.