De-repression and subsequent induction of protease synthesis by Bacillus mojavensis under fed-batch operations

Bacillus mojavensis produced 440 U ml(-1) of an alkaline protease during batch-fermentation at 50 degreesC in a minimal medium containing casamino acids. Enzyme production was inducible in the presence of organic nitrogen, was maximal in casein and casamino acids and was repressed by glucose and ammonium ions. A fed-batch strategy was adopted to enhance protease synthesis by using intermittent de-repression and induction during the growth of the organism. In the first biomass production phase, the growth of the bacterium was achieved in non-inducible conditions for 6 h in the presence of glucose and ammonium ions. Feeding of casamino acids at this stage resulted in a 2.8-fold (1219 U ml(-1)) increase in protease yield after 36 h compared to the protease yield in batch culture. This protease production was enhanced further to fourfold (1770 U ml(-1)) in the second fed-batch operation on the onset of the second stationary phase by a glucose feed (5 mg ml(-1)) at 33 h followed by a casamino acids feed (5 mg ml(-1)) at 36 h. The overall fermentation process was highly sensitive to agitation and protease production was drastically inhibited at low agitation conditions and only negligible amounts of protease was produced in static culture. (C) 2002 Elsevier Science Ltd. All rights reserved.