PH regulation of recombinant glucoamylase production in Fusarium venenatumJeRS 325, a transformant with a Fusarium oxysporum alkaline (trypsin-like)protease promoter

Fusarium venenatum (formerly Fusarium graminearum) JeRS 325 produces hetero logous glucoamylase (GAM) under the regulation of a Fusarium oxysporum alka line (trypsin-like) protease promoter. The glucoamylase gene was used as a reporter gene to study the effects of ammonium and pH on GAM production und er the control of the alkaline protease promoter. Between pH 4.0 and 5.8, G AM production in glucose-limited chemostat cultures of JeRS 325 grown at a dilution rate of 0.10 h(-1) (doubling time, 6.9 h) on (NH4)(2)SO4 medium in creased in a linear manner with increase in pH. However, at pH 4.0 and belo w GAM production was almost completely repressed in glucose-limited chemost at cultures grown on (NH4)(2)SO4 or NaNO3 medium. Thus GAM production in Je RS 325 is regulated by culture pH, not by the nature of the nitrogen source in the medium. The difficulty of using unbuffered medium when investigatin g putative ammonium repression is also shown. The study demonstrates the po tential for use of the alkaline protease promoter in F. graminearum for the production of recombinant proteins in a pH dependent man ner. (C) 1999 Joh n Wiley & Sons, Inc.