BIOTECHNOLOGY: AN OVERVIEW

Substrates For Biotechnology

Fermenter Technology

1) All materials coming into contact with the solutions entering the fermenter or the actual organism culture must be corrosion resistant to prevent trace metal contamination of the process.
2) The materials must be non-toxic so that slight dissolution of the material or components does not inhibit culture growth.
3) The materials of the fermenter must withstand repeated sterilization with high pressure steam.
4) The fermenter stirrer system, entry ports and end plates must be sufficiently rigid not to be deformed or broken under mechanical stress.
5) Visual inspection of the medium and culture is advantageous, transparent materials should be used where ever possible.

Genetics and Biotechnology

So far, biotechnology has been considered with respect to two characteristics: obtaining the best catalyst and the best environment. The most effective, stable and convenient form for the biocatalyst is a whole organism. In most cases, this could be some type of microbe like bacterium, yeast, or mold. Originally, these microorganisms were extracted from the natural environment, but today, scientists can genetically alter these into superior organisms. This is a practice that is being carried out by most biological-based industries and is direct result of the close cooperation between technologists and geneticists.
Genetic recombination occurs during normal sexual reproduction and consists of the breakage and rejoining of DNA molecules of the chromosomes and is of vital importance to living organisms. Generally, there are strong taxonomic constraints that confine the naturally occurring mechanisms which permit genetic recombination to take place. In contrast, recombinant DNA techniques known as genetic engineering offer unlimited opportunities for bringing about new combinations of genes which at the moment do not exist under natural conditions. Genetic engineering has been defined as 'the formation of new combinations of heritable material by the insertion of nucleic acid molecules, produced by whatever mean outside the cell, into any virus, bacterial plasmid or other vector system so as to allow their incorporation into a host organism in which they do not naturally occur but in which they are capable of continued propagation'. The following are strategies involved in genetic engineering:
1) Formation of DNA fragments: Extracted DNA can be cut into small sequences by way of specific enzymes, restriction endonucleases found in many species of bacteria.
2) Splicing of DNA into vectors: The small sequences of DNA can be joined or spliced into the vector DNA molecules by an enzyme DNA ligase creating an artificial DNA molecule.
3) Introduction of vectors into host cells: The vectors are either viruses or plasmids, and are replicons and can exist in cells in an extrachromosomal state; transfer normally by transduction or transformation.
4) Selection of newly acquired DNA: Selection and ultimate characterization of the recombinant clone.
These methods allow totally new functions to be added to the capabilities of industrial microorganisms. What earlier seemed impractical by microbial manipulation is now possible. Examples will include the synthesis in microorganisms of specific animal proteins such as insulin, enhanced ranges of enzymes, hormones, anti-tumor and anti-viral compounds (interferon), fine chemicals or bulk chemicals such as ethanol, or creating the ability to utilize complex substrates such as cellulose and lignin and to produce worthwhile products from them. Genetic engineering holds the potential to extend the range and power of every aspect of biotechnology.

Single Cell Protein Production

One of the biggest problems facing the world today is population growth, especially in developing nations. At present there are 4 billion mouths to be fed and if the growth rate continues, by the year 2000, this number will exceed 5 billion. Conventional agriculture may not be able to a sufficient supply of food and, in particular, protein. The search for protein is relently pursued. Today, new agricultural practices are widespread, high protein cereals have been developed, the cultivation of soybeans and groundnuts is ever expanding, etc. After all this, the use of microbes as protein producers has gained wide experimental success. This field of study has become known as single cell protein production (SCP) and refers to the fact that most of the microorganisms used as producers grow as single or filamentous individuals rather than as complex multicellular organisms like plants or animals.
There are many reasons why microbes are the prime candidate for SCP production, some of which include: 1) microorganisms can grow at remarkably rapid rates under optimum conditions: some microbes can double their mass every 0.5-1 hour, 2) microorganisms are more easily modified genetically than plants and animals: they are more amenable to large-scale screening programmes to select for higher growth rate, improved amino acid content etc. and can be more easily subjected to gene transfer technology, 3) microorganisms have relatively high protein content and the nutritional value of the protein is good, 4) microorganisms can be grown in vast numbers in relatively small continuous fermentation processes using relatively small land area and are also independent of climate, and 5) microorganisms can grow on a wide range of raw materials, in particular low value wastes, and can also use plant-derived cellulose.
The acceptability of SCP, when presented as human food, depends not only on its safety and nutritional value, but also on other factors. People don't usually fancy the idea of eating food derived from microbes. In many cultures, there are guidelines of what you can and cannot eat. Also, odor, color, taste, and texture need to be taken into consideration when dealing with peoples' desires. Thus, if SCP is to be used as direct food for man, then the skills of the food technologist will be greatly challenged.

Enzyme Technology

Enzymes are complex organic molecules present in living cells where they act as catalysts in bringing about chemical changes in substances. The subject of biochemistry has provided us with a more profound understanding of enzymes. Although enzymes are only formed in living cells, they can also live in vitro. The usage of enzymes in industrial processes to aid in different types of chemical transformations has led to the name enzyme technology. Enzyme technology embraces production, isolation, purification, use in soluble form and finally the immobilization and use of enzymes in a wide range of reactor systems. Enzymes will aid in problem such as food production, energy shortage and preservation, and improvement of the environment.
Although many useful enzymes have been derived from plant and animal sources, it is anticipated that most future developments in enzyme technology will rely on enzymes of microbial origin. The use of microorganisms as a source material for enzyme production has developed for several important reasons: 1) There is normally a high specific activity per unit dry weight of product, 2) Seasonal fluctuations of raw materials and possible shortages due to climatic changes or political upheaval do not apply, 3) In microbes, a wide spectrum of enzyme characteristics, such as pH range and temperature resistance is available for selection, and 4) Industrial genetics has greatly increased the possibilities for optimizing enzyme yield and type through strain selection, mutation, induction and selection of growth conditions and, more recently, by using the innovative powers of gene transfer technology.
Immobilization of enzymes on insoluble polymers, such as membranes and particles, which act as supports or carriers for the enzyme activity, is a new and valuable area of enzyme technology. The enzymes become physically confined during a continuous catalytic process and may be recovered from a reaction mixture and re-used over and over again, thus improving the economy of the process. In this way, it has been found that some enzymes that are rapidly inactivated by heat when in cell-free form can be stabilized by attachment to inert polymeric supports while in other examples such insolubilized enzymes can be used in non-aqueous environment. Whole microbial cells can also be immobilized inside polyacrylamide beads and used for a wide range of catalytic functions. The variety of new enzymes and whole organism systems that are likely to become cheaply available presents exciting possibilities for the future. Present application of immobilized catalysts are mainly confined to industrial processes, for example production of L-amino acids, organic acids and fructose syrup.

Biological Fuel Generation

We are slowly depleting our fossil fuel energy resulting in the need to seek out alternative sources of energy. So far, these have included the harnessing of hydro, tidal, wave and wind power, the capture of solar and geothermal energy supplies, and nuclear power. There is now a growing appreciation of biological solar energy systems and biotechnological advances in this area will soon bring economic reality to selected processes. As fossil fuel resources are depleted and become increasingly more expensive, conversion of organic residues to liquid fuels will become a more economically attractive consideration.
There are three main directions that can be followed to achieve biomass supplies: 1) cultivation of so-called energy crops, 2) harvesting of natural vegetation, and 3) utilization of agricultural and other organic wastes. The conversion of the resulting biomass to usable fuels can be accomplished by either biological or chemical means or by a combination of both. The two main end products that will be formed will be either methane or ethanol although other products may arise depending on initial biomass and the processes utilized, for example solid fuels, hydrogen, low-energy gases, methanol and longer-chain hydrocarbons.
Although biomass may ultimately only supply a relatively small amount of the world's energy requirements, it will nevertheless be of immense overall value. In some parts of the world, such as Brazil and countries of similar climatic conditions, biomass will surely attain wider exploitation and utilization. There may still be some disadvantages when comparing it with coal or oil, but the very fact that it is renewable and they are not must be the spur to further research. In time, biomass will become much more easily and economically used as a source of energy for mankind.

Biotechnology and Medicine

Antibiotics are antimicrobial compounds produced by living organisms and are used therapeutically and sometimes prophylactically in the control of infectious disease. Over 4000 antibiotics have been isolated but only about 50 have achieved wide usage. The other antibiotic compounds failed to achieve commercial importance because of their toxicity to man or animals, lack of producing the desired effect, or high production costs.
Antibiotics may function over a wide range of microorganisms and are termed 'broad spectrum', for example chloramphenicol and the tetracyclines which can control such unrelated organisms as the rickettsiae, chalamydiae, and mycoplasma. In contrast, streptomycin and penicillin are examples of narrow spectrum antibodies being effective against only a few bacterial species. Most antibiotics have been derived from the actinomycetes and the mould fungi.
Thus, in medicine, biotechnology will have an increasing importance in the production of new and improved products that will contribute to the well-being of mankind. Such benefits must not be limited only to the developed nations and it must be hoped that the new medically related biotechnologies can be transferred in some form to the more needy developing countries where disease are still such crippling forces.

Environmental Technologies

Waste can be considered as any material or energy form that cannot be economically used, recovered or recycled at a given time and place. Growth in human populations has generally been matched by a greater formation of a wider range of waste products, many of which cause serious environmental pollution if they are allowed to accumulate in the ecosystem. In rural communities recycling of human, animal and vegetable waste has been practiced by man for centuries, providing in many cases valuable fertilizers or fuel. In urban communities where most of the deleterious wastes accumulate efficient waste collection and specific treatment processes have been developed since it is impractical to discharge high volumes of waste into natural land and waters. The development of these practices in the last century was one of the main reasons for the spectacular improvement in health and well being of the community.
Mainly by empirical means a variety of biological treatment systems have been developed, ranging from cess pits, septic tanks and sewage farms to gravel beds, percolating filters and activated sludge processes coupled with anaerobic digestion. The primary aims of all of these systems or biotreaters is to alleviate health hazards and to reduce the amount of oxidizable organic compounds and thus produce a final effluent or outflow which can be discharged into the natural environment without producing any adverse affects. Biotreaters rely on the metabolic versatility of mixed microbial populations for their efficiency. The fundamental feature of biotreaters is that they should contain a range of microorganisms with the overall metabolic capacity to degrade any compound entering the system. Controlled use of microorganisms has lead to the virtual elimination of such water-borne disease as typhoid, cholera, and dysentery in industrialized communities.

Postscript

This short report has attempted to analyze some of the important areas of biotechnology. The focus was on the organism aspects of biotechnology and not on the more complex areas such as dewatering, drying, and extraction/purification. We shouldn't expect to much to soon from biotechnology. There are some very promising results that have been obtained from on going experiments, but there is still a long way to go. Things like insulin and monoclonal antibodies should become available quite quickly while things like biofuels could still take a few decades.