Bioethanol Production by Enzymatic Hydrolysis and Fermentation of Cocoyam

Abstract

Bioethanol, produced by anaerobic fermentation of carbohydrates with microorganism is a liquid fuel used either as energy source or as an additive/enhancer for fossil petrol. This research was carried out to explore the potential of cocoyam starch as an alternative feedstock for bioethanol production. Cocoyam corms and cormels were peeled, dried and milled to flour, the slurries were then mashed with different enzyme cocktails comprising of amylase, glucoamylase and protease enzymes. The saccharified wort obtained was fermented with yeast; Saccharomyces cerevisiae without exogenous nutrient supplementation. Two fermentation processes were employed. Simultaneous Saccharification and Fermentation (SSF) and Separate Hydrolysis and Fermentation (SHF). Glucose liberated during mashing was determined by glucose oxidase method and it was found that enzymatic hydrolysis of cocoyam flour was effective in yielding favourable levels of fermentable glucose up to 86g glucose/100g substrate with batch 1 of enzymes. Ethanol production was measured from the cocoyam mash and it was found that S. cerevisiae produced ethanol levels equating to 398 L/ton which compares favourably with yields from cassava 280 L/ton and corn 420 L/ton. These observations indicated that cocoyam can serve as a very cheap alternative biomass for bioconversion to bioethanol with minimal inputs.