Evaluating the Potential of Wild Cocoyam “Caladium Bicolor” for Ethanol Production Using Indigenous Fungal Isolates☆

Abstract Ethanol is a renewable bio-fuel which impacts the environment minimally. Different plant materials have been assessed as carbon source for bio-ethanol production in previous studies. In the present study, flour from peeled tuber of Caladium bicolor (wild cocoyam) was used as the carbon source and microorganisms isolated from rotten C. bicolor tubers and palm wine were utilized for the fermentation. This research was aimed at using indigenous microbial isolates and wild cocoyam (non-edible) as substrates for bio-ethanol production. Eighteen fungal strains were isolated from rotten tubers of C. bicolor and fresh palm wine and thereafter screened for amylase production and fermentation capability. The best isolate was used to optimize reducing sugar production by varying the fermentation parameters (time, pH, substrate concentration, and nitrogen source and inoculum size). The results obtained revealed nine isolates with high starch degrading ability. Aspergillus spp. were found to be the predominant microorganisms and Aspergillus sp. (Org 2) gave the highest amylolytic activity with a concentration of 6.019 mg/ml reducing sugar during submerged fermentation. Under optimal conditions (pH 5, 5% substrate concentration, 0.5% soya bean and 2% inoculum size (1.0 x 10 8 spores/ml), on day 5) results from hydrolysis showed that the highest amount of reducing sugar produced was 6.989 mg/ml. The hydrolysate was further fermented using Saccharomyces sp. (4.0 x 10 7 cells/ml) at pH 5.2 for144 hours. The fermented liquid was then distilled to yield a maximum ethanol concentration of 0.485%. This study demonstrates that indigenous microbial isolates and substrates when properly propagated and processed can be utilized for amylase and ethanol production.