Statistical media optimization and alkaline protease production from Bacillus mojavensis in a bioreactor

Alkaline protease production in Bacillus mojavensis was improved up to 4.2-fold in a 14 1 bioreactor during validation of a predicted statistical model. The final enzyme yield in the bioreactor was 2389 U ml(-1) obtained within 10-12 h compared to 558 U ml(-1) after 24 h in shake flask cultures. Analysis of variance (ANOVA) of face-centered central composite design showed a high coefficient of determination (R-2) value of 0.9473, thus ensuring a satisfactory adjustment of the quadratic model with the experimental data. The coordinates of three factors (casamino acids, inoculum age and agitation) were positive, whereas negative coordinates were obtained for other two factors (glucose and incubation time). Protease production was subjected to catabolite repression by glucose ( > 2 mg ml(-1)). The response surface curves predicted increased levels of casamino acids (12 mg ml(-1)) and midlevel of glucose (2 mg ml(-1)) as best C/N combination for optimal enzyme production (1133 U ml(-1)) within 18 h at high agitation rates ( > 250 rpm) and low inoculum density (A(550) (mm) congruent to 0.250). Protease production was drastically reduced at low agitation rates. The present study provides useful information about the regulation of protease synthesis through manipulation of various physicochemical factors. (C) 2003 Elsevier Ltd. All rights reserved.