Bioethanol Production from Rice Straw Enzymatically Saccharified by Fungal Isolates, Trichoderma viride F94 and Aspergillus terreus F98

Mervate A Abo-State,Nour Sh El-Gendy,Ahmed M E Ragab,Hekmat R Madian,Laila A Farahat

doi:10.4236/soft.2014.32003

Abstract

Egypt faces a high population growth rate nowadays, which demands for an increase in agricultural production efficiency. Consequently, agricultural field residues will increase. Rice straw is one of the main agriculture residues in Egypt. So this study was performed on rice straw as a resource for production of bioethanol. Eight microbial isolates, five yeasts and three fungi were isolated from rice straw. Yeast isolates were selected for their ability to utilize different sugars and cellulose. Chipped and grinded rice straw was subjected to different pretreatment methods physically through steam treatment by autoclaving and different doses of gamma γ irradiation (50 and 70 Mrad). Autoclaved pretreated rice straw was further enzymatically treated throughout solid state fermentation process by different fungal isolates; F68, F94 and F98 producing maximum total reducing sugars of 12.62, 13.58, 17.00 g/L, respectively. Bioethanol production by separate microbial hydrolysis and fermentation (SHF) process of rice straw hydrolysate was performed by the two selected fungal isolates; Trichoderma viride F94 and Aspergillus terreus F98 and two yeast isolates (Y26 and Y39). The two yeast isolates have been identified by 18S, RNA as Candida tropicalis Y26 and Saccharomyces cerevisiae Y39. SHF processes by F94 and Y26 produced 45 gallon/ton rice straw while that of F98 and Y39 produced 50 gallon/ton rice straw.

Highlights

IntroductionIncreasing gas prices and environmental concerns, in recent years, have become the driving force for developing altersnative energy sources, especially fuel ethanol for automobiles [1]
Increasing gas prices and environmental concerns, in recent years, have become the driving force for developing altersnative energy sources, especially fuel ethanol for automobiles [1].Ethanol is a clean-burning renewable resource that can be produced from fermented cellulosic biomass [2]
The aim of this study is to examine different physical and enzymatical pretreatments of rice straw and the ability of isolated fungal strains to form fermentable sugars by secreting different cellulases through solid state fermentation process

Summary

Introduction

Increasing gas prices and environmental concerns, in recent years, have become the driving force for developing altersnative energy sources, especially fuel ethanol for automobiles [1]. Ethanol is a clean-burning renewable resource that can be produced from fermented cellulosic biomass [2]. Ethanol does not add to a net-CO2 atmospheric increase, there is no contribution to global warming. Combustion of ethanol results in relatively low emissions of volatile organic compounds, carbon monoxide and nitrogen oxides [3]. The importance of the biomass based ethanol production has undergone a huge increase in the last few years. Further cost reduction is still essential for large deployment of this new technology. Since the cost of the traditionally used (sugar and starch-containing) raw materials represent the major part of the total production cost, constitutes about 40% - 70% of the production cost [4], using less valuable materials, like agricultural waste, could reduce the expense significantly [5] [6]

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