GOAL-ORIENTED SCREENING METHOD FOR CARBOHYDRATE OXIDASES PRODUCED BY FILAMENTOUS FUNGI

A rapid and convenient screening method for the in situ detection of microbial carbohydrate oxidases was developed on the basis of a H2O2-dependent, peroxidase-catalyzed chromogenic reaction with ABTS. Thus, out of more than 100,000 colonies, obtained from 300 different soil samples, 166 colonies were identified by the dye formation from the chromogen. The corresponding colonies were isolated, purified, and identified as filamentous fungi. Following growth in liquid cultures, both mycelial extracts and culture supernatants of all isolates were assayed for the occurrence of carbohydrate and polyol oxidase activities, respectively. Both activities were negligible in supernatants, but present in the mycelial extracts of most of the isolates. The specific activities determined with various sugar substrates ranged from 1 to 100 mU mg-1 protein. The specific activities determined with polyol substrates were two orders lower, and therefore were considered to be marginal activities of preexisting carbohydrate oxidases. With slight modifications, this screening method should be generally applicable to the detection of all kinds of oxidases, laccases, phenol oxidases, and peroxidases.