Multi-objective based superimposed optimization method for enhancement of l-glutaminase production by Bacillus subtilis RSP-GLU

Abstract

l-Glutaminase (l-glutamine amidohydrolase, EC 3.5.1.2) is a deamiding enzyme that has current focus on a therapeutic potentials and flavor enhancement agent in food industry. It was noticed that the amidase production was depended on the bacterial growth. However, the enhancement of bacterial growth by other substrates suppress the secretion of l-glutaminase. Governing the growth as well as amidase production is challenging task. In this study a multi-objective based superimposed optimization method was employed to control the biomass as well as to enhance the production of l-glutaminase. Various parameters such as volume of medium, pH, incubation temperature, inoculum level, l-glutamine concentration and rpm were optimized. The interactive influence of these parameters with their effect on enzyme and biomass production was analyzed using fractional factorial central composite design (FFCCD). The coefficient of determination (R2) was calculated as 0.9862 and 0.9513 for l-glutaminase and biomass production respectively. Overlay graphs were plotted by superimposing the contours for the various response surfaces of biomass and enzyme production. Based on superimposing method the cultural conditions obtained was volume of media 85 mL, temperature 37 °C, pH 7.24, inoculum concentration 2.47 mL, l-glutaminase concentration 1.01 g/L and agitation speed of 109 rpm. At these conditions 225 U/mL l-glutaminase and 0.79 g/L biomass were obtained. The current study provides a good description for balanced optimization of fermentation process of multi response or objective systems by using FFCCD method.