Biochemical transformations of herbicide-derived anilines in culture medium and in soil

Abstract

A correlation was established between peroxidase activity of soil and its capacity to transform 3,4-dichloroaniline, a breakdown product of several herbicides, to 3,3′,4,4′-tetrachloroazobenzene. Supplementation of soil by carbon and nitrogen sources for microbial growth stimulated both activities, and pointed to the microbial origin of soil peroxidases. Several peroxidase-producing bacteria, actinomycetes, and fungi were isolated from soil and were characterized. On the basis of its rapid growth and high peroxidase activity, a Geotrichum candidum strain was selected for further study. The culture filtrate of this organism exhibited both peroxidase and aniline oxidase activity. The highest per milligram dry weight activity of these enzymes was observed after cultivation on a mineral salts medium supplemented with soil extract and yeast extract.