Comparative Studies on Production of Bioethanol from Rice Straw Using Bacillus subtilis and Trichoderma viride as Hydrolyzing Agents

Abstract

Ethanol production by S. cerevisiae was carried out using rice straw as substrate and B. subtilis and T. viride as hydrolyzing agents. The aim of this research is to compare the potential of rice straw (non-edible waste material) for bioethanol production using Bacillus subtilis and Trichoderma viride as cellulose hydrolyzing agents. The sample was dried and ground; and was subjected to chemical pretreatment and microbial hydrolysis to maximize sugar production. Standard methods were used to carry out isolation, identification and analysis of sample which includes proximate, mineral and physicochemical analysis. The sample was fermented for seven days during which ethanol yield was determined. Cellulose hydrolysis screening carried out on each of the two organisms revealed T. viride having the higher clearance zone of 1.8 cm, while B. subtilis had 1.5 cm. Proximate analysis obtained from the samples showed that the pretreatment method was relatively effective giving an increase in the cellulose and decrease in the hemicellulose and lignin contents of the samples. This showed rice straw having a cellulose content of 51.33 ± 0.17% after pretreatment. Potassium content was relatively high (17.96 mg/g), Hydrolysis using T. viride gave higher reducing sugar yield than that obtained using B. subtilis with 26.6 g and 12.21 g respectively. The pH was observed to decrease during fermentation while total titratable acidity observed showed an increase. Highest ethanol yield of 16.21 g/100 g was obtained using T. viride as hydrolyzing agent.