Fibrinolytic enzyme production from low-cost substrates by marine Bacillus subtilis: Process optimization and kinetic modeling

Enhanced fibrinolytic enzyme production was achieved by systematic process optimization, using marine Bacillus subtilis D21-8 under submerged batch fermentation. A low-cost medium containing 23.2 g/L soybean meal, 24.1 g/L cassava starch and 1.6 g/L CaCl2 was attained by single factor experiments combined with statistical methods. The environmental conditions, optimized in a 250 mL shake flask, were 34 degrees C, 220 rpm and initial pH 5.0-5.2. Scale-up experiments were performed in fermenters with different oxygen supply. The highest fibrinolytic activity of 3787 U/mL was obtained in 100 L pilot fermenter with aeration rate of 1.0 vvm, which is among the highest reported in literature in terms of fibrinolytic enzyme production from cheap substrates. Kinetic modeling of the batch fermentation processes in fermenters using Logistic and Luedeking-Piret equations enables obtaining an improved insight of process kinetics.