Optimization of culture conditions for keratinase production of Bacillus tropicus KRKJVR 5 by using RSM (Response Surface Methodology)

This study aimed to optimize the production of keratinase by Bacillus tropicus KRKJVR 5 using response surface methodology (RSM). The factors considered were temperature (20 to 40°C), pH (5 to 9), inoculum size (0.5 to 2.5%), incubation period (24 to 120 hours) and agitation speed (RPM) (50 to 350). A total of 32 experimental runs were conducted based on the central composite design (CCD) model, with observed keratinase activity ranging from 2.00 to 13.33 U/mL. The highest keratinase activity (13.33 U/mL) was observed under the conditions of 30°C temperature, pH 7.0, 1.5% inoculum size, 72 hours incubation period and 150 RPM. The lowest activity (2.00 U/mL) was recorded at extreme conditions of low pH (3.0) and high temperature (50°C), highlighting the sensitivity of keratinase production to these factors. The regression analysis revealed a significant model with an R-squared value of 93.78%, indicating a strong fit to the data. The ANOVA results further supported the significance of these factors, with the overall model being highly significant (F-Value = 8.30, P-Value = 0.000). The contour plots demonstrated the optimal conditions for maximizing keratinase activity. The study effectively identified the optimal conditions for keratinase production by Bacillus tropicus KRKJVR 5 using response surface methodology. The results indicate that a temperature of 30°C, pH of 7.0, inoculum size of 1.5%, incubation period of 72 hours, and agitation speed of 150 RPM are ideal for producing high levels of keratinase. These findings provide valuable insights for scaling up the process for industrial applications, emphasizing the importance of precise control over culture conditions to achieve high enzyme yields.