Microbial Secondary Metabolites Production and Strain Improvement

Microbial secondary metabolites are compounds produced mainly by actinomycetes and fungi, usually late in the growth cycle (idiophase). Although antibiotics are the best known secondary metabolites (SM), there are others with an enormous range of other biological activities mainly in fields like: pharmaceutical and cosmetics, food, agriculture and farming. These include compounds with anti-inflammatory, hypotensive, antitumour, anticholesterolemic activities, and also insecticides, plant growth regulators and enviromnental friendly herbicides and pesticides. These compounds are usually produced by liquid submerged fermentation, but some of these metabolites could be advantageously produced by solid-state fermentation. Today, strain improvement can be performed by two alternative strategies, each having distinct advantages, and in some cases all these approaches can be used in concert to increase production such as classical genetic methods with mutation and random selection or rational selection (including genetic recombination); and molecular genetic improvement methods. The latter can be applied by: amplification of SM biosynthetic genes, inactivation of competing pathways, disruption or amplification of regulatory genes, manipulation of secretory mechanisms and expression of a convenient heterologous protein. It is visualized that in the near future, genomics will also be applied to industrial strain improvement.