Strain improvement for fermentation and biocatalysis processes by genetic engineering technology.

Twenty years ago, the first complete gene cluster encoding the actinorhodin biosynthetic pathway was cloned and characterized. Subsequently, the gene clusters encoding the biosynthetic pathways for many antibiotics were isolated. In the past decade, breakthroughs in technology brought that generation of rationally designed or new hybrid metabolites to fruition. Now, the development of high-throughput DNA sequencing and DNA microarray techniques enables researchers to identify the regulatory mechanisms for the overproduction of secondary metabolites and to monitor gene expression during the fermentation cycle, accelerating the rational application of metabolic pathway engineering. How are the new tools of biotechnology currently being applied to improve the production of secondary metabolites? Where will this progress lead us tomorrow? The use of whole cells or partially purified enzymes as catalysts has been increased significantly for chemical synthesis in pharmaceutical and fine-chemical industries. The development of PCR technologies for protein engineering and DNA shuffling is leading to the generation of new enzymes with increased stability to a wide range of pHs, temperatures and solvents and with increased substrate specificity, reaction rate and enantioselectivity. Where will this emerging technology lead us in the twenty-first century?