Using Bacillus subtilis 168 for ε-Research on Optimization of Polylysine Fermentation Conditions

Abstract

In this experiment, the optimization of ε-polylysine fermentation conditions using the fermentation method was performed by first determining the content of the relevant components in the culture medium through a one-way experiment to observe the effect on the experiment. In the one-way experiment, the optimal values of the factors affecting the medium were determined under different conditions. Since fermentation optimization through one-way experiments alone is a time-consuming and laborious process, and the variables that produce the best response are often not identified. Based on the experimental data obtained from single-factor experiments, after comprehensive consideration of optimization, it can be investigated by response surface methodology. Response surface methodology (RSM) is a statistical technique used to empirically model and assess the impact of variables by varying one independent variable while fixing all other variables at certain levels. By using statistical methods to optimize all impact parameters, the limitations of the optimization process in single-factor experiments can be eliminated and many factors can be quickly screened to capture the effects of interactions between these factors. In this study, we attempted to isolate a strain of Bacillus that can produce ε-PL and optimize the experimental data for the production of ε-PL using statistical methods to achieve the goal of increasing the yield of ε-PL through reasonable culture conditions. The optimization of M3G medium in this study was primarily conducted through one-way experiments and response surface methodology to identify the key factors influencing the yield of ε-polylysine based on experimental data, aiming to determine optimal ratios for enhancing ε-polylysine production. By investigating the impact of carbon source, nitrogen source, and inorganic salt on ε-polylysine production through Bacillus subtilis 168 fermentations, we have successfully developed an optimized culture formulation for efficient ε-polylysine production: glucose addition at a quantity of 60.3 g/L, yeast powder addition at a quantity of 7.49 g/L, ammonium sulfate addition at a quantity of 12.1 g/L. The predicted yield of ε-polylysine reached 0.3365 g/L. The optimal conditions were carefully selected for the shake flask fermentation experiment of ε-polylysine in order to ensure the accuracy of the experiments conducted in this response surface method. Three replications were 0.306±0.006 g/L. These Findings provide a solid experimental foundation for further fermentation production.