Escherichia coli host engineering for efficient metagenomic enzyme discovery
Reia Hosokawa-Okamoto and Kentaro Miyazaki
from: Metagenomics: Current Innovations and Future Trends (Edited by: Diana Marco). Caister Academic Press, U.K. (2011)
Enzymes are environmentally friendly biocatalysts that are widely used in modern life, e.g., in food processing, laundry detergent, and production of medicinal compounds. An increasing demand to shift focus from petrochemicals to biotechnology-based industries has expanded the use of enzymes. To date, most industrially relevant enzymes are of microbial origin. Therefore, mining for microbial enzymes is key to the development of the biotechnology industry; however, less than 1% of environmental bacteria can be cultured in the laboratory at present. To accelerate the discovery of industrially relevant enzymes, it would therefore be advantageous to employ a metagenomic approach to extend the available microbial sources to presently 'unculturable' taxa. However, such an approach also risks a low hit rate; typically, only a few positives are obtained from the hundreds of thousands of library clones screened. This is largely because of the discrepancy between the host's transcriptional/translational machineries and the genetic signals present in the metagenomes. Escherichia coli has long been used as a generic host for cloning and production purposes and is, in most instances, suitable for this purpose. However, several modifications are necessary to overcome the problems of heterologous gene expression. In this chapter, we discuss several approaches that may be useful for developing the utility of E. coli as a host for efficient functional screening of metagenomic libraries read more ...