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ENHANCEMENT OF CELLULOSIC ETHANOL PRODUCTION THROUGH ASPERGILLUS NIGER MODIFICATION

ABSTRACT

Simultaneous Saccharification and Fermentation (SSF) were carried out to produce ethanol from maize stalk in 500ml conical flask. Aspergillus niger strains were isolated from four difference sources, maize stalk, soil, bambaranut, rotten wood. Cellulose degrading ability was screened by zone of clearance carried out by simple agar method.. Apergillus strain from rotten wood (ANRW) produced the largest zone of clearance of 6.5mm; hence it was selected for further studies. The effect of pH, temperature, substrate particle size, and substrate concentration were studies and optimized to be 5.0, 3oC, 300um, 3% respectively.Aspergillus niger was modified using UV irradiation technique by varying the exposure timings. The strain expose at 30 minutes gave largest zone of clearance and hence was selected. The ethanol yield by simultaneous saccharification and fermentation of modified and unmodified strain of A. niger and saccharomyces cerevisae isolate from burkutu by Debo in Micro biology department ABU Zaria was compared at optimum condition pH 5.0,temperature 30oC, 3%, substrate concentration and 300um substrate particle respectively. The mutant strain from the UV irradiation gave the maximum ethanol yield of 9.3g/100ml which is higher than that of parent strain 3.4g/100ml.

CHAPTER ONE

1.0 INTRODUCTION

In view of continuously rising petroleum cost and dependence upon fossil fuel resources, considerable attention has been focused on alternative energy resources. Production of ethanol or ethyl alcohol [CH3CH2CH2OH] from biomass is one way to reduce both the cost of consumption of crude oil and environmental pollution. Ethanol represents an important, renewable liquid fuel for motor vehicles (Lewis, 1996). The use of bioethanol as an alternative motor fuel has been steadily increasing around the world for a number of reasons. Domestic production and use of ethanol for fuel can decrease dependence on foreign oil, reduce trade deficits, create jobs in rural area, reduce air pollution, and reduce global climate change due to carbon dioxide buildup.

Ethanol unlike gasoline is an oxygenated fuel that contains 35% oxygen, which reduces particulate and NO2 emission from combustion. When burned, ethanol derived from fermentation produces no net increase in carbon dioxide in the atmosphere. It is an octane enhancing additive and removes free water which can plug fuel lines in cold climates (Lang et al; 2001). Ethanol is the most widely used liquid biofuel. It is an alcohol and is produced from sugars, starches or from cellulosic biomass. Most commercial production of ethanol is from sugar cane or sugar beet, as starches and cellulosic biomass usually require expensive pretreatment. Bioethanol is used as a renewable energy fuel source as well as for manufacture of cosmetics, pharmaceuticals and also for the production of alcoholic beverages.