Chapter 3 : Identifying Novel Microbial Catalysis by Enrichment Culture and Screening

Abstract:

Enrichment culture is an experimental method which has been used extensively by microbiologists to obtain bacteria in monotypic, or pure, culture. Enrichment culture has yielded key information on the metabolic activities and genes of thousands of microorganisms. A pure culture offers a range of techniques for revealing the molecular details of biodegradation. Enrichment culture techniques allow selective cultivation of one or more bacterial strains obtained from a complex mixture such as that found in most soils. The method typically relies on using a particular organic compound as the sole carbon source or, less frequently, as the nitrogen, sulfur, or phosphorus source. In enrichment cultures conducted for obtaining a desired biocatalyst, a given pathway or reaction might be assumed; the goal is to obtain an enzyme of a known type which is highly active with a given substrate or under a specific set of conditions. In this case, the screening method is important, as it might be necessary to look at hundreds or thousands of enzymes yielded in the first round of screening. Another approach is to test existing strains to determine if they have the enzyme of interest and will show high activity with the substrate of interest. In this context, a limited taxonomic range of organisms is typically screened. The fungi screened include Aspergillus, Fusariiim, Trichoderma, Mucor, and Rhizomucor. These genera are known to produce a host of hydrolytic biodegradative enzymes of importance in industry. The enzymes include cellulase, lipase, and rennilase.