Keywords: l-Methioninase, Pseudomonas stutzeri , Media component, Statistical optimization, Kinetic modeling
In this study, Pseudomonas stutzeri has been explored as new bacterial strain for producing intracellular l-methioninase. Kinetic modeling and optimization of fermentation conditions are crucial parameters for improving production of l-methioninase. Response surface methodology has been employed as fast efficient technique for investigating the interactive effect of culture condition parameters for l-methioninase. Plackett–Burman design was first employed for screening significant variables for production media components including glucose, l-methionine, NaCl, malt extract and casein enzymic hydrolysate. The optimal level of these significant media components was further optimized using Central composite design. The high value of determination of coefficient (R2 = 0.95) showed the good fitness of these statistical models for explaining the relationship between variables and response. The optimum values for the investigated variables were obtained as 5% glucose, 0.25% l-methionine, 0.2% malt extract, 1% casein enzymic hydrolysate and 1% NaCl. The maximum production of l-methioninase was obtained as 240.97 U/l after performing the experiments at these optimum data variables, which was increased by 1.61-fold in compare to classical method. The kinetic study was further performed at these optimum media components and the production of l-methioninase was found as non-growth associated behavior. Logistic equation and modified Luedeking–Piret equation were further employed to develop mathematical model for growth kinetic and production kinetic. These results would be significant for large scale production of these enzymes using bioreactors in industry.
The authors would like to thank Department of Bioscience and Biotechnology of Banasthali Vidyapith, Rajasthan, India, to provide lab facility and research support to carry out this research work.