Enhancement Of Cellulosic Ethanol Production Through Aspergillus Niger Modification

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 of Enhancement Of Cellulosic Ethanol Production Through Aspergillus Niger Modification

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.

Being abundant and outside
the human food chain makes cellulosic materials relatively inexpensive inputs for ethanol
production. Vast quantities of agricultural and agro- industrial residues that are generated as a
result of diverse agricultural practices represent the most important energy rich resources.

Accumulation of this biomass in large quantities every year results not only in pollution of the
environmental but in a loss of valuable materials which can be processed to yield food, fuel, feed
and variety of chemicals.

Some examples of these agricultural wastes are, maize stalk, corn bran,
rice bran, cotton linten, sugar cane, bagasse, wheat straw, corn cob, saw dust among others. The
major components of these residues are cellulose and hemicelluloses (75 – 80%) while lignin
comprises only 14% [Bowen and Harper, 1989]. Cellulose is the basic component of plant
material and is produced in greater quantity than any other substance.

It makes up about 50% of
the total organic carbon in the biosphere while lignin is a polymeric substance that is
quantitatively the most important component of plant after cellulose and hemicelluloses.

These agricultural residues which are dumped indiscriminately in the environment have
constituted environmental pollution problem, but various studies and research have shown that
these residues can be biologically exploited for the synthesis of chemicals and fuels [Zadrazil,
1985; Buswell and Odier, 1987, Raid, 1989].

The presence of lignin polysaccharide bonds in
these ligno-cellulosic tissues severally limits the efficient bioconversion of these residues into
valuable agro-industrial product [Smith et al., 1986].

However, some form of treatment had been
employed to maximize these high fibre plant residues Chemical and physical delignification
techniques had been used with limited success [Milestein et al., 1987] while the use of biological
treatment methods had proved widely favorable [Reid, 1985; Zadrazil et al., 1990].

Aerobic microorganisms such as fungi, mycobacterial, eubacteria and few anaerobic organisms (fungi,
protozoa, and bacteria) had been discovered to be able to degrade cellulose [Barton, 1979]. Fungi
play a significant role in the degrading or bioconversion of cellulose under aerobic conditions.
1.1 RESEARCH PROBLEM
This research was designed to address the following problems:
i. Waste cellulose materials are being burnt, buried or otherwise discarded indiscriminately,
thus causing environmental pollution.
ii. The conversion of cellulose biomass to useful substances such as liquid fuels through the
enzymatic hydrolysis of polysaccharide into fermentable sugar is still too low.
1.2 AIM
To modify Aspergillus niger for enhancing bioethanol production from maize stalk using
simultaneous saccharification and fermentation (SSF) by Aspergillus niger and Sacchromyses
Cerevisiae
1.3 RESEARCH OBJECTIVES
a. To isolate and screen strains of Aspergillus niger for cellulose degrading ability.
b. To determine the optimum fermentation conditions that favor production of bioethanol
from maize stalks using simultaneous saccharification and fermentation.
c. To modify Aspergillus niger using ultraviolent (UV) light to enhance hydrolysis.
d. To compare the ethanol yield of UV irradiated Apergillus niger and treated Apergillus
niger by simultaneous saccharification and fermentation (SSF). (Aspergillus niger and
saccharonyces cerevisiae).
e. To analyze the produced bioethanol by qualitative infrared spectrum test.
1.5 JUSTIFICATION
Maize stalks are renewable resources that are inexpensive, readily available and present in large
quantities in Nigeria. In addition, converting maize stalks into valuable product (bioethanol)
provides a potential alternative fuel to the fossil-based fuels, which has long drained our national
resources.

Conversion of these waste materials equally helps in converting their environmental
pollution to wealth. This will also reduce the sources of Green House Gases which contribute to
Global Warming.
1.5 SCOPE
This work covers the following:
 Screening for degrading ability of Aspergillus niger isolates
 Optimizing the fermentation culture conditions such as temperature, pH, substrate
particle size and concentration.
 Analysis of the produce bio-ethanol from maize stalk by quantitative infrared spectrum
test.
1.6 LIMITATION
Certain factors that limit this research are: erratic power supply, inefficient/poor equipment used.

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