Enhancement of cellulosic ethanol production through aspergillus niger modification

Thesis Overview

<p> INTRODUCTION<br>In view of continuously rising petroleum cost and dependence upon fossil fuel resources,<br>considerable attention has been focused on alternative energy resources. Production of ethanol or<br>ethyl alcohol [CH3CH2CH2OH] from biomass is one way to reduce both the cost of consumption<br>of crude oil and environmental pollution. Ethanol represents an important, renewable liquid fuel<br>for motor vehicles (Lewis, 1996). The use of bioethanol as an alternative motor fuel has been<br>steadily increasing around the world for a number of reasons. Domestic production and use of<br>ethanol for fuel can decrease dependence on foreign oil, reduce trade deficits, create jobs in rural<br>area, reduce air pollution, and reduce global climate change due to carbon dioxide buildup.<br>Ethanol unlike gasoline is an oxygenated fuel that contains 35% oxygen, which reduces<br>particulate and NO2 emission from combustion. When burned, ethanol derived from<br>fermentation produces no net increase in carbon dioxide in the atmosphere. It is an octane<br>enhancing additive and removes free water which can plug fuel lines in cold climates (Lang et al;<br>2001).<br>Ethanol is the most widely used liquid biofuel. It is an alcohol and is produced from sugars,<br>starches or from cellulosic biomass. Most commercial production of ethanol is from sugar cane<br>or sugar beet, as starches and cellulosic biomass usually require expensive pretreatment.<br>Bioethanol is used as a renewable energy fuel source as well as for manufacture of cosmetics,<br>pharmaceuticals and also for the production of alcoholic beverages. Being abundant and outside<br>the human food chain makes cellulosic materials relatively inexpensive inputs for ethanol<br>production. Vast quantities of agricultural and agro- industrial residues that are generated as a<br>result of diverse agricultural practices represent the most important energy rich resources.<br>Accumulation of this biomass in large quantities every year results not only in pollution of the<br>environmental but in a loss of valuable materials which can be processed to yield food, fuel, feed<br>and variety of chemicals. Some examples of these agricultural wastes are, maize stalk, corn bran,<br>rice bran, cotton linten, sugar cane, bagasse, wheat straw, corn cob, saw dust among others. The<br>major components of these residues are cellulose and hemicelluloses (75 – 80%) while lignin<br>comprises only 14% [Bowen and Harper, 1989]. Cellulose is the basic component of plant<br>material and is produced in greater quantity than any other substance. It makes up about 50% of<br>the total organic carbon in the biosphere while lignin is a polymeric substance that is<br>quantitatively the most important component of plant after cellulose and hemicelluloses.<br>These agricultural residues which are dumped indiscriminately in the environment have<br>constituted environmental pollution problem, but various studies and research have shown that<br>these residues can be biologically exploited for the synthesis of chemicals and fuels [Zadrazil,<br>1985; Buswell and Odier, 1987, Raid, 1989]. The presence of lignin polysaccharide bonds in<br>these ligno-cellulosic tissues severally limits the efficient bioconversion of these residues into<br>valuable agro-industrial product [Smith et al., 1986]. However, some form of treatment had been<br>employed to maximize these high fibre plant residues Chemical and physical delignification<br>techniques had been used with limited success [Milestein et al., 1987] while the use of biological<br>treatment methods had proved widely favorable [Reid, 1985; Zadrazil et al., 1990]. Aerobic<br>microorganisms such as fungi, mycobacterial, eubacteria and few anaerobic organisms (fungi,<br>protozoa, and bacteria) had been discovered to be able to degrade cellulose [Barton, 1979]. Fungi<br>play a significant role in the degrading or bioconversion of cellulose under aerobic conditions.<br>1.1 RESEARCH PROBLEM<br>This research was designed to address the following problems:<br>i. Waste cellulose materials are being burnt, buried or otherwise discarded indiscriminately,<br>thus causing environmental pollution.<br>ii. The conversion of cellulose biomass to useful substances such as liquid fuels through the<br>enzymatic hydrolysis of polysaccharide into fermentable sugar is still too low.<br>1.2 AIM<br>To modify Aspergillus niger for enhancing bioethanol production from maize stalk using<br>simultaneous saccharification and fermentation (SSF) by Aspergillus niger and Sacchromyses<br>Cerevisiae<br>1.3 RESEARCH OBJECTIVES<br>a. To isolate and screen strains of Aspergillus niger for cellulose degrading ability.<br>b. To determine the optimum fermentation conditions that favor production of bioethanol<br>from maize stalks using simultaneous saccharification and fermentation.<br>c. To modify Aspergillus niger using ultraviolent (UV) light to enhance hydrolysis.<br>d. To compare the ethanol yield of UV irradiated Apergillus niger and treated Apergillus<br>niger by simultaneous saccharification and fermentation (SSF). (Aspergillus niger and<br>saccharonyces cerevisiae).<br>e. To analyze the produced bioethanol by qualitative infrared spectrum test.<br>1.5 JUSTIFICATION<br>Maize stalks are renewable resources that are inexpensive, readily available and present in large<br>quantities in Nigeria. In addition, converting maize stalks into valuable product (bioethanol)<br>provides a potential alternative fuel to the fossil-based fuels, which has long drained our national<br>resources. Conversion of these waste materials equally helps in converting their environmental<br>pollution to wealth. This will also reduce the sources of Green House Gases which contribute to<br>Global Warming.<br>1.5 SCOPE<br>This work covers the following:<br>ï‚— Screening for degrading ability of Aspergillus niger isolates<br>ï‚— Optimizing the fermentation culture conditions such as temperature, pH, substrate<br>particle size and concentration.<br>ï‚— Analysis of the produce bio-ethanol from maize stalk by quantitative infrared spectrum<br>test.<br>1.6 LIMITATION<br>Certain factors that limit this research are: erratic power supply, inefficient/poor equipment used. <br></p>