Turkish Journal of Biology




Production of alkaline protease from B. licheniformis N-2 was studied in shake flask experiments in growth medium comprised of (g/l): glucose, 10; soybean meal, 10; K_2HPO_4, 5; MgSO_4.7H_2O, 0.5; NaCl, 0.5; CaCl_2.2H_2O, 0.5. Different process parameters, such as fermentation period, initial pH, incubation temperature, agitation speed, and size and age of inoculum, were optimized for the maximum yield of the alkaline protease. Maximum enzyme production (991.04 PU/ml) was obtained after 24 h of incubation at 37 °C in growth medium of pH 10. The optimum inoculum size and age were determined as 2.0% (v/v) and 24 h, respectively. Kinetics of growth and protease production by this microorganism were also analyzed at all optimum conditions. Biomass (Y_{x/s}) and product yield (Y_{p/s}) coefficients were determined as 0.375 g of cells/g of glucose and 99.3 PU/g of glucose, with a growth rate of (0.215 h^{-1}) after 24 h of incubation. Thereafter, a continuous decrease in biomass and product yield was observed. The results indicate that enzyme production by B. licheniformis N-2 was entirely growth-associated and that a major portion of the enzyme was secreted in the post exponential phase.


Process parameters, growth kinetics, alkaline protease, Bacillus licheniformis N-2

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