Microbial Biotechnology: fundamentals of applied microbiology

Microbes (or microorganisms) are organisms that are too small to be seen by the unaided eye. They include bacteria, fungi, protozoa, microalgae, and viruses.

Microbes live in familiar settings such as soil, water, food, and animal intestines, as well as in more extreme settings such as rocks, glaciers, hot springs, and deep-sea vents. The wide variety of microbial habitats reflects an enormous diversity of biochemical and metabolic traits that have arisen by genetic variation and natural selection in microbial populations.

Historically, humans have exploited some of this microbial diversity in the production of fermented foods such as bread, yogurt, and cheese. Some soil microbes release nitrogen that plants need for growth and emit gases that maintain the critical composition of the Earth's atmosphere.

Other microbes challenge the food supply by causing yield-reducing diseases in food-producing plants and animals. In our bodies, different microbes help to digest food, ward off invasive organisms, and engage in skirmishes and pitched battles with the human immune system in the give-and-take of the natural disease process.

A genome is the totality of genetic material in the DNA of a particular organism. Genomes differ greatly in size and sequence across different organisms. Obtaining the complete genome sequence of a microbe provides crucial information about its biology, but it is only the first step toward understanding a microbe's biological capabilities and modifying them, if needed, for agricultural purposes.

Microbial biotechnology, enabled by genome studies, will lead to breakthroughs such as improved vaccines and better disease-diagnostic tools, improved microbial agents for biological control of plant and animal pests, modifications of plant and animal pathogens for reduced virulence, development of new industrial catalysts and fermentation organisms, and development of new microbial agents for bioremediation of soil and water contaminated by agricultural runoff.

Microbial genomics and microbial biotechnology research is critical for advances in food safety, food security, biotechnology, value-added products, human nutrition and functional foods, plant and animal protection, and furthering fundamental research in the agricultural sciences.

NIFA has identified four major related research objectives:

• Assure that the complete nucleic acid sequences of high priority beneficial and detrimental agricultural microorganisms are available in public databases.
• Assure that the agricultural research community has adequate resources and facilities available for the functional analysis of agricultural microbes (for example, expression array technologies, proteomics, relational databases, and other bioinformatics tools) so that practical benefits are not delayed.
• Support training and extension for microbial genomics and its evolving technologies.
• Foster U.S. interests through national and international public and private partnerships in microbial genomics, and, through such partnerships, facilitate capacity development in the United States and abroad that ensures public access and appropriate use of intellectual property.

Microbial biotechnology has a variety of useful applications in agriculture.

Assessing and managing environmental risks from transgenic microorganisms is an important issue for which scientists have developed research needs and priorities.

The mapping of microbial genomes is a key technology to understanding microorganisms and devising ways to improve their use in agricultural production, food safety, and bio-based chemicals. For more, see the Microbial Genomics program page.

 

 

23)Fermentation Biotechnology: principles, processes and products
A general definition of fermentation is an energy-yielding anaerobic metabolic process in which organisms convert nutrients (typically carbohydrates) to alcohols and acids (lactic acid and acetic acid).

The most commonly known definition for fermentation is the conversion of sugar to alcohol, using yeast, under anaerobic conditions, as in the production of beer or wine, vinegars and cider.

However, in biotechnology, the term is used more loosely to refer to growth of microorganisms on food, under either aerobic or anaerobic conditions.

Fermentation tanks, also called bioreactors, used for industrial fermentation processes are glass, metal or plastic tanks, equipped with gages and settings to control aeration, stir rate, temperature, pH and other parameters of interest. Units can be small enough for bench-top applications (5-10 L) or up to 10,000 L in capacity for large-scale industrial applications. Fermentation units such as these are used in the pharmaceutical industry for the growth of specialized pure cultures of bacteria, fungi and yeast, and the production ofenzymes and drugs.

Microbial fermentations may be classified into the following major

group^:^

(i) Those that produce microbial cells (biomass) as the product.

(ii) Those that produce microbial metabolites.

(iii) Those that produce microbial enzymes.

(iv) Those that modify a compound which is added to the fermenta-

tion - the transformation processes.

(v) Those that produce recombinant products.

Before the fermentation is started the medium must be formulated and sterilized, the fermenter sterilized, and a starter culture must be available in sufficient quantity and in the correct physiological state to inoculate the production fermenter. Downstream of the fermenter the product has to be purified and further processed and the effluents produced by the process have to be treated.

 

25 Factors influence on androgenesis and ginogenesis processes. Factors affecting androgenesis. Genotype. The choice of starting material for an anther or microspore culture project is of the utmost importance. In particular, genotype plays a major role in determining the success or failure of an experiment. Haploid plant production via androgenesis has been very limited or nonexistent in many plant species.condition of donor plants. The age and physiological condition of donor plants often affect the outcome of androgenesis experiments. As a general rule, anthers should be cultured from buds collected as early as possible during the course of flowering. Various environmental factors that the donor plants are exposed to may also affect haploid plant production. Light intensity, photoperiod, and temperature have been investigated, and at least for some species, these are found to influence the number of plants produced from anther cultures. STAGE OF MICROSPORE DEVELOPMENT. The most critical factor affecting haploid production from anther and microspore culture is the stage of microspore development; for many species, success is achieved only when anthers are collected during the uninucleate stage of pollen development. In many cases, anthers within a bud are sufficiently synchronized to allow this one anther to represent the remaining cultured anthers. PRETREATMENT. For some species, a pretreatment following collection of buds, but before surface disinfestation and excision of anthers, has been found to be beneficial. For any one species, there may be more than one optimum temperature and length of treatment combination. In general, lower temperatures require shorter durations, whereas a longer pretreatment time is indicated for temperatures at the upper end of the cold pretreatment range mentioned above. TEMPERATURE AND LIGHT. Various cultural conditions, such as temperature and light, may also affect androgenic response. Anther cultures are usually incubated at 24 to 25˚ C. In some species, an initial incubation at a higher or lower temperature has been beneficial. Some species respond best when exposed to alternating periods of light and dark, whereas continuous light or dark cultural conditions have proven beneficial in other species. MEDIA. Cytokinin is sometimes used in combination with auxin, especially in species in which a callus phase is intermediate in the production of haploid plants. FACTORS AFFECTING GYNOGENESIS. GENOTYPE. Gynogenesis has not been investigated as thoroughly or with as many species as has androgenesis; therefore, less information is available concerning the various factors that contribute to the successful production of haploids from the female than the male gametophyte. However, several studies have identified genotype as a critical factor in determining the success of an gynogenesis experiment. Not only are there differences between species, but genotypes within individual species have responded differently. As with androgenesis, it is important to include a wide range of genotypes in ovule and ovary culture experiments. MEDIA. Media has also been identified as an important factor in gynogenesis. The most commonly used basal media for recovering gynogenic haploids are MS, B-5 (Gamborg et al., 1968), Miller’s (Miller, 1963), or variations on these media. Sucrose levels have ranged from 58 mM to 348 mM (2–12%). While gynogenic haploids have developed in a few species without the use of growth regulators, most species have required auxins and/or cytokinins in the medium. For those species that undergo indirect gynogenesis, both an induction and a regeneration medium may be required. Most ovule and ovary culture experiments have been conducted using solid medium. A list of specific media components used for gynogenesis in several crop species can be found in Keller and Korzun (1996). STAGE OF GAMETOPHYTIC DEVELOPMENT. Because the female gametophyte is difficult to handle and observe, determining the optimum stage of gametophytic development for gynogenesis is usually based on other, more easily discerned,230 Plant Development and Biotechnology characteristics. Performance of ovule and ovary cultures has often been correlated with stage of microspore development. Depending on species, the best results have been obtained when the female gametophyte was cultured from the late uninucleate to trinucleate stage of megaspore development. In other studies, number of days until anthesis has been used as an indicator of stage of gametophytic development. A few gynogenesis studies that involved direct observations of the female gametophyte have been conducted. For several species, gynogenesis was most successful where cultures were initiated when the embryo sac was mature or almost mature (for review, see Keller and Korzun, 1996). OTHER FACTORS. Cold pretreatment of flower buds at 4˚ C for 4 to 5 days has been effective in increasing yields of haploid embryos or callus in a few species, but has not been widely investigated. Seasonal effects have been observed in several species. Many of the other factors that affect androgenesis probably also affect gynogenesis; however, in most cases, insufficient data is available to detect trends in response. These variables should, however, be considered when initiating gynogenesis experiements