Role of Genetic Engineering in Fermentation Technology

Role of Genetic Engineering in
Fermentation Technology
Submitted by : Saima Siddique
Submitted to : Sir Tahir Baig
: UG-3
Biotechnology is the application of scientific and engineering principles to the processing of different
materials with biological agents to provide goods and services. Essentially, biotechnology harnesses the
catalytic power of biological systems, whether by direct use of enzymes or through the use of the
intricate biochemistry of whole cells and micro-organisms. Biotechnology involves the use in industry of
living organisms or their components i.e. enzyme. It includes the introduction of genetically engineered
micro-organisms into a variety of industrial processes. Because nearly all the products of biotechnology
are manufactured by micro-organisms, fermentation is an indispensable element of biotechnology’s
support system. Defined in this way, biotechnology encompasses everything from the technology of
bread-making to that implicated in the manufacture of human insulin from a bacterium induced to take
up a non-bacterial gene and produce the protein coded by that gene.
The potential of biotechnology for increasing agricultural productivity is high, in terms of both increasing
the yields of cultivated plants and of obtaining foodstuffs with higher nutritional value. Numerous
foodstuffs are manufactured using fermentation, and enzymes are now widely used as processing aids in
food manufacturing. Acetone, citric acid, ethanol, and other chemicals are, or have been, produced
industrially by fermentation.
For centuries natural fermentation processes have been used to produce products including cheese,
yoghurt and beer. On the other hand, since the birth of genetic engineering (1970s), genes have been
spliced between different types of micro-organims in order to enable the production of products using
transgenic E.coli bacterium and other micro-organisms. At present, transgenic E.coli bacterium are used
in production of almost all manner of things including chymosin (as required in the making of cheese), as
well as human growth hormones, synthetic insulin and first generation bioplastics and biofuels.
Over the years, the scope and efficiency of the fermentation process has been gradually improved and
refined. Two processes now exist, both of which will benefit from genetic engineering.
 In fermentation technology, living organisms provide miniature factories, converting raw
materials into end products.
In enzyme technology, biological catalysts take from living organisms are utilized to make the
The food processing, chemical, and pharmaceutical industries are the three major users of fermentation
The food industry was the first one to exploit micro-organisms to produce alcoholic beverages
and fermented foods.
In the early 20th century, the chemical industry began to use the technology to produce
organic solvents like ethanol, and enzymes like amylase, used at the time to treat textiles.
About thirty years later after the World War II, the pharmaceutical industry followed the
chemical industry’s lead, applying fermentation to the production of vitamins and new
Today, approximately 200 companies in the United States and over 500 worldwide use fermentation
technologies to produce a wide variety of products. Most use them as part of production processes,
usually in food processing. But others manufacture either proteins, which can be considered primary
products, or a host of secondary products, which these proteins help produce. For genes can make
enzymes, which are proteins; and the enzymes can help make alcohol, methane, antibiotics, and many
other substances.
Fermentation technologies are so useful for producing proteins partly because these are the direct
products of genes. But proteins in the form of enzymes can also be used in thousands of additional
conversions to produce practically any organic chemical and many inorganic ones as well.
Originally, fermentation used some of the most primitive forms of plant life as cell factories e.g.
Bacteria were used to make yogurt and antibiotics
Yeasts to ferment wine
The filamentous fungi or molds to produce organic acids
More recently, fermentation technology has begun to use cells derived from higher plants and animals
under growth conditions known as cell or tissue culture. In all cases, large quantities of cells with
uniform characteristics are grown under defined, controlled conditions.
At present, it is still uncertain whether the use of whole cells or isolated enzymes will be more useful in
the long run. There are advantages and disadvantages to each. With isolated enzymes, genetic
manipulation can readily increase the supply of enzymes, while with whole organisms, a wide variety of
manipulations is possible in constructing more productive strains.
Although live yeast had been used for several thousand years in the production of fermented foods and
beverages, it was not until 1878 that the active agents of the fermentation process were given the name
“enzymes” (from the Greek, meaning “in yeast”). The inanimate nature of enzymes was demonstrated
less than two decades later when it was shown that extracts from yeast cells could effect the conversion
of glucose to ethanol. Finally, their actual chemical nature was established in 1926 with the purification
and crystallization of the enzyme urease.
Fermentation carried out by live cells provided the conceptual basis for designing fermentation
processes based on isolated enzymes. A single enzyme situated within a living cell is needed to convert a
raw material into a product. A lactose-fermenting organism, e.g., can be used to convert the sugar
lactose, which is found in milk, to glucose (and galactose). But if the actual enzyme responsible for the
conversion is identified, it can be extracted from the cell and used in place of a living cell. The purified
enzyme carries out the same conversion as the cell, breaking down the raw material in the absence of
any viable micro-organism. An enzyme that acts inside a cell to convert a raw material to a product can
also do this outside of the cell.
Applied genetics is intimately tied to fermentation technology, since finding a suitable species of microorganism is usually the first step in developing a fermentation technique. Until recently, geneticists have
had to search for an organism that already produced the needed product. However, through genetic
manipulation a totally new capability can be engineered; micro-organisms can be made to produce
substances beyond their natural capacities.
The most striking successes have been in the pharmaceutical industry, where human genes have been
transferred to bacteria to produce insulin, growth hormone, interferon, thymosin a-1, and somatostatin,
In general, once a species is found, conventional methods have been used to induce mutations that can
produce even more of the desired compound. The geneticist searches from among hundreds of mutants
for the one micro-organism that produces most efficiently.
The current industrial approach to fermentation technologies therefore considers two problems:
First, whether a biological process car produce a particular product
Second, which micro-organism has the greatest potential for production and how the desired
characteristic can be engineered for it.
Finding the desired micro-organism and improving its capability is so fundamental to the fermentation
industry that geneticists have become important members of fermentation research teams.
Genetic engineering can increase an organism’s productive capability (a change that can make a
process economically competitive) but it can also be used to construct strains with
characteristics other than higher productivity.
Properties such as objectionable color, odor, or slime can be removed.
The formation of spores that could lead to airborne spread of the microorganism can be
The formation of harmful byproducts can be eliminated or reduced.
Other properties, such as resistance to bacterial viruses and increased genetic stability, can be
given to micro-organisms that lack them.
Applying recent genetic engineering techniques to the production of industrially valuable enzymes may
also prove useful in the future.
Genetic engineering is not in itself an industry, but a technology used at the laboratory level. It allows
the researcher to alter the hereditary apparatus of a living cell so that the cell can produce more or
different chemicals, or perform completely new functions. The altered cell, or more appropriately the
population of altered identical cells is, in turn, used in industrial production. It is within this framework
that the impacts of applied genetics in the various industries is examined.
Regardless of the industry, the same three criteria must be met before genetic technologies can become
commercially feasible. They include the need for:
1. a useful biochemical product;
2. a useful biological fermentation approach to commercial production; and
3. a useful genetic approach to increase the efficiency of production.
The three criteria interrelate and can be met in any order; the demonstration of usefulness can begin
with any of the three. Insulin, e.g., was first found to have value in therapy; fermentation was then
shown to be useful in its production; and, now genetic engineering promises to make the fermentation
process economically competitive. In contrast, the value of thymosin a-1, has not yet been proved,
although the usefulness of genetic engineering and fermentation in its production have been
In the past, enzyme engineering required the prior knowledge of the 3-D structure of the enzyme before
any rational design of mutation could be carried out. Twenty years ago, the first complete gene cluster
encoding the actinorhodin biosynthetic pathway was cloned and characterized. Afterwards, the gene
clusters encoding the biosynthetic pathways for many antibiotics were isolated. In the past decade,
breakthroughs in technology brought that generation of rationally designed or new hybrid metabolites
to completion. Now, the development of high-throughput DNA sequencing and DNA microarray
techniques enables researchers to identify the regulatory mechanisms for the overproduction of
secondary metabolites and to monitor gene expression during the fermentation cycle, accelerating the
rational application of metabolic pathway engineering.
The use of whole cells or partially purified enzymes as catalysts has been increased significantly for
chemical synthesis in pharmaceutical and fine-chemical industries. The development of PCR
technologies for protein engineering and DNA shuffling is leading to the generation of new enzymes
 Increased stability to a wide range of pHs, temperatures and solvents
 Increased substrate specificity, reaction rate and enantioselectivity .
Using genetic engineering techniques, the objectives for enzyme engineering have been mostly
Yeasts have been used to produce food and beverages since the Neolithic age. Their use in fermentation
was recognized in 1836–1838; and Louis Pasteur demonstrated their unequivocal role in the conversion
of sugar to ethanol and carbon dioxide in 1861.
Originally, fermentation was spontaneous. The first pure yeast culture was obtained by Emil Christian
Hansen from the Carlsberg Brewery in 1883. A pure culture of wine yeast was subsequently obtained by
Müller-Thurgau from Geisenheim (Germany) in 1890. The genetic improvement of industrial strains
traditionally relied on classical genetic techniques (mutagenesis, hybridization, protoplast fusion,
cytoduction), followed by selection for broad traits such as fermentation capacity, ethanol tolerance,
absence of off-flavors (e.g. H2S for wine strains), fast dough fermentation, osmotolerance, rehydration
tolerance, organic acid resistance (baker’s strains), flocculation and carbohydrate utilization (brewer’s
One major advantage of gene technology over classical genetic techniques is that just one characteristic
can be precisely modified, without affecting other desirable properties. In addition, molecular biology
approaches have introduced a new dimension. The expression of heterologous genes has substantially
increased the possibilities. In the past 20 years, impressive progress has been made in the development
of molecular techniques for Saccharomyces cerevisiae. These advances have been successfully applied
to industrial strains in the past decade, allowing the development of a new generation of specialized
industrial yeast strains. The principal targets for strain development fall into two broad categories:
(1) improvement of fermentation performance and simplification of the process and
(2) improvement of product quality, e.g. organoleptic and hygienic characteristics.
A few yeasts are known to ferment xylose directly to ethanol. However, the rates and yields need to be
improved for commercialization. Xylose utilization is repressed by glucose which is usually present in
lignocellulosic hydrolysates, so glucose regulation should be altered in order to maximize xylose
conversion. Xylose utilization also requires low amounts of oxygen for optimal production. Respiration
can reduce ethanol yields, so the role of oxygen must be better understood and respiration must be
reduced in order to improve ethanol production. This is being made possible by using genetic
Xylose is the second most abundant carbohydrate in the lignocellulosic biomass hydrolysate. The
fermentation of xylose is essential for the bioconversion of lignocelluloses to fuels and chemicals. A few
yeasts are known to ferment xylose directly to ethanol. However, the rates and yields need to be
improved for commercialization. Wild-type strains of Saccharomyces cerevisiae are unable to utilize
xylose. A modified genome shuffling method were developed to improve xylose fermentation by S.
cerevisiae. Recombinant yeast strains were constructed by recursive DNA shuffling with the
recombination of entire genome of P. stipitis with that of S. cerevisiae. After two rounds of genome
shuffling and screening, one potential recombinant yeast strain ScF2 was obtained. It was able to utilize
high concentration of xylose and produced ethanol. The recombinant yeast ScF2 produced ethanol more
rapidly than the naturally occurring xylose-fermenting yeast.
OTA (Office of Technology Assessment). Commercial Biotechnology: An International
Analysis. OTA-BA-218. January. Washington, D.C.: Government Printing Office. 1984
“Strain improvement for fermentation and biocatalysis processes by genetic engineering
technology”: Shu-Jen Chiang , Society for Industrial Microbiology.
“The potential of genetic engineering for improving brewing, wine-making and baking
yeasts”:S.Dequin, : 19 April 2001 / Accepted: 20 April 2001 / Published online: 15 June 2001 ©
Springer-Verlag 2001
“Ethanol fermentation from biomass resources: current state and prospects”: Yan Lin . Shuzo
Tanaka (
“Genetic engineering for improved xylose fermentation by yeasts”: Jeffries TW, Shi NQ. USDA,
Forest Service, Institute for Microbial and Biochemical Technology, Madison, WI 53705, USA.
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