Bioethanol Production by Immobilized Saccharomyces cerevisiae using Different Lignocellulosic Materials

Abstract

Ethanol from biomass is an attractive and sustainable energy source for transportation fuel to substitute gasoline. Second generation ethanol production utilizes cheaper and non-food feed stocks like lignocelluloses or municipal solid waste. This, could make ethanol more competitive to fossil fuels. The aim of the present study is the production of low cost ethanol using the agro wastes like tomato waste and wheat straw and make a comparison between the efficiency of free and immobilized yeast cells in calcium alginate beads with microwave-assisted acidic pretreatment of the lignocellulosic materials. We have investigated the efficiency of immobilization technique for bioethanol production using Saccharomyces cerevisiae isolate which isolated from yogurt. This isolate was identified according to morphological and biochemical characterization tests. Microwave-assisted acidic pretreatment was performed for both wheat straw and tomato waste and show high improvement (45%) in glucose sugar amount compared with conventional mode of heating of dilute 7% HCl or 5% H2SO4 hydrolysis. Calcium alginate was used as immobilization matrix for S. cerevisiae. The best calcium alginate concentration was 3% and 4 % for reference and isolated yeast respectively. The immobilization technique gave higher ethanol yield compared with free system for tomato waste but lower yield with wheat straw. The maximum amount of ethanol (641mg/g) produced  by free cells  when used pretreated straw with microwave-assisted 5%H2SO4 hydrolysis and (543.5 mg/g) for tomato waste using immobilized cells with microwave-assisted 7%HCl hydrolysis.