Kinetics of lipopeptides production of tilapia processing byproduct fermentation by Bacillus natto NT-6 in solid state

A 60 h solid state fermentation experiment was conducted to investigate the production technology of tilapia sp. byproduct as an antimicrobial product and source of nutritious feed. Crushed tilapia sp. byproduct and water was put in a triangular flask and then inoculated with 5% Bacillus Natto NT-6 with fermentation temperature at 30 °C. Studies on changes in pH, temperature, ratio of water and enzymatic activity during the fermentation process was conducted. In addition to this, modelling of the antimicrobial concentration of the biomass and protein concentration was done. Analysis of the relationship between these parameters and lipopeptide yield was also made. The results showed that during fermentation the biomass increased for 48 h, then stabilized, the maximum growth rate was 0.2355×10⁸ cfu/h. The production trend of lipopeptide is same as the biomass, the maximum yield was 7.3 g/kg and the maximum generation rate was 0.1112 g/h. The bacteria (B. Natto NT-6) secreted a high amount of enzymes, extraordinarily,the protease enzymatic activity was as highly as 30 304.56 U/g. During the process, the temperature, pH and water content of the substrate was fluctuating slightly. On the bases of Logistic and material balance equation, the model of bacteria growth kinetics, comprehensive product generation and substrate consumption were set up and the non-linear fitting was employed to model the kinetics of fermentation by the software Origin 8.5. At the time,the models and the experimental data were well fitted and the relative error non-significant. The model developed in this study could predict the concentration of surfactin in biomass, substrate consumption and also help to determine whether the fermentation process was normal or not. This would enable a sound scientific control of surfactin fermentation process in real-time. This is of great significance to antimicrobial lipopeptides at large-scale production and application.