Growth-rate-independent production of recombinant glucoamylase by Fusariumvenenatum JeRS 325

Most recombinant proteins generated in filamentous fungi are produced in fe d-batch cultures, in which specific growth rate normally decreases progress ively with time. Because of this, such cultures are more suited to the prod uction of products that are produced efficiently at low-growth rates (e.g., penicillin) than to products which are produced more efficiently at high-g rowth rates (e.g., glucoamylase). Fusarium venenatum A3/5 has been transfor med (JeRS 325) to produce Aspergillus niger glucoamylase (GAM) under the co ntrol of the Fusarium oxysporum trypsin-like protease promoter. No glucoamy lase was detected in the culture supernatant during exponential growth of F . venenatum JeRS 325 in batch culture. In glucose-limited chemostat culture s, GAM concentration increased with decrease in dilution rate, but the spec ific production rate of GAM (g GAM [g biomass](-1) h(-1)) remained approxim ately constant over the dilution-rate range 0.05 h to 0.19 h(-1), i.e., the recombinant protein was produced in a growth-rate-independent manner. The specific production rate decreased at dilution rates of 0.04 h(-1) and belo w. Specific production rates of 5.8 mg and 4.0 mg GAM [g biomass](-1) h(-1) were observed in glucose-limited chemostat cultures in the presence and ab sence of 1 g mycological peptone L-1. Compared to production in batch cultu re, and for the same final volume of medium, there was no increase in gluco amylase production when cultures were grown in fed-batch culture. The resul ts suggested that a chemostat operated at a slow dilution rate would be the most productive culture system for enzyme production under this trypsin-li ke promoter. (C) 2000 John Wiley & Sons, Inc.