Microbes have a number of advantages, including rapid uptake of nutrients supporting high rates of metabolism and biosynthesis; ability to carry out a wide variety of reactions; facility to adapt to a large array of different environments; ease of genetic manipulation, both in vivo and in vitro, to increase production, to modify structures and activities, and to make entirely new products; simple screening procedures; and a wide diversity.
Microbial products are diverse, ranging from large molecules such as proteins, nucleic acids, carbohydrate polymers, or even cells, to small molecules that are usually divided into primary metabolites, i.e., those essential for vegetative growth, and secondary metabolites, which are not essential for growth. The primary metabolites include amino acids, organic acids, alcohols, and vitamins.
Production of a particular primary metabolite by deregulated organisms may inevitably be limited by the inherent capacity of the particular organism to make the appropriate biosynthetic enzymes. Recent approaches utilize modern genetic engineering techniques to correct such deficiencies and develop strains overproducing primary metabolites.
There are two ways to accomplish this: increase the number of copies of structural genes coding for these enzymes and the frequency of transcription.
Novel genetic technologies are important for the development of overproducers. Genome-based strain reconstruction leads to the development of a superior strain which contains mutations crucial to hyperproduction but not other unknown mutations, which accumulate by brute-force mutagenesis and screening.
Also important are genome-sequencing projects involving hundreds of genomes, the availability of sequences corresponding to model organisms, new DNA microarray and proteomic tools, and new techniques for mutagenesis and recombination DNA technology.