A directed approach to the selection of bacteria with enhanced catabolic activity

Aims: This study was aimed at selecting catabolically-improved bacteria by in vitro evolution using a specially designed fermentor system. Methods and Results: To facilitate this objective, genetic variation was in duced by ultraviolet irradiation, and a selective pressure was subsequently exerted by gradual increases in the concentration of organic toxins. Durin g a pilot experiment, a culture was forced to tolerate and catabolize a mix ture of phenol and formaldehyde. The population developed a high resistance against formaldehyde and the specific degradation rate increased rapidly. Biochemical analysis of the mutants revealed an increase in the expression of enzymes involved in the pathway oxidizing formaldehyde. Conclusions: The fermentor system described is, in general, suitable for th e selection of bacteria with enhanced catabolic activities. Significance and Impact of the Study: The procedure is an alternative to co nventional genetic engineering, providing efficient and genetically stable strains suitable for applications in the field of environmental biotechnolo gy.