Molecular Improvement of Fungal Strains
Genetics plays a significant role in the strain improvement of industrially important microorganisms, whether the species is prokaryotic or eukaryotic. To carry out any of the molecular genetic method for strain improvement, identification of biosynthetic pathway, adequate vectors and appropriate transformation protocols should be developed. Among microorganisms, fungi and actinomycetes have been successfully developed for industrial applications. Several species of filamentous fungi are known to produce pharmaceuticals, antibiotics, metabolites, phytohormones, and other industrially important products. There is a great deal of interest to
utilize the potential of filamentous fungi as biocontrol agents, antagonists of other fungal phytopathogens, bioherbicides and as bioinsecticides (Kapoor, 1995). Genetic engineering methods have also provided tools to know in detail the nature of the modifications occurred (Barrios-González, 2003). Genetic technology can improve the performance of microorganisms by altering spectrum of metabolites as well as altering the species growth characteristics. In addition, microbes can be made to produce novel products by rDNA technology with appropriate screening. Genetic manipulations are employed in industries to improve the production rate and quality by the originally isolated strain. Today, classical method has been replaced by modern strategic technologies developed via advances in molecular biology, recombinant DNA technology, and genetics to improve strain. The implementation of strain improvement methods has increased fermentation productivity and decreased costs tremendously. Additionally, these genetic programs also serve other goals such as the elimination of undesirable products or analogs, discovery of new antibiotics, and deciphering of biosynthetic pathways (Demain and Adrio, 2008). Previously, scientists selected microbial strains from natural ecosystem that fulfilled both microbiological and technical requirements for economical production processes. Later, genetically modified strains with novel properties were developed through classical strain improvement methods relying mostly on random mutagenesis. In recent years, recombinant technologies have contributed extensively to production enhancement. The design and generation of new transformation strategies to manipulate specific gene expression and function in diverse filamentous fungi, including those having a biotechnical significance has been achieved by better understanding of fundamental genetic processes. With developments in genetic engineering and molecular biology, filamentous fungi have also achieved increased attention as hosts for recombinant DNA. Considerable success has been achieved in the increased production of variety of fungal products such as secondary metabolites, enzymes and proteins (Schwab, 1988; Archer and Peberty, 1997; Wang et al., 2005; Kuck and Hoff, 2010).