Study on TCS fermentation kinetic models and high-density culture strategy.

This study enhanced the production efficiency of Lacticaseibacillus casei TCS by optimizing medium composition and fermentation conditions for high-density culture. Initially, single-factor and orthogonal experimental designs and the response surface methodology were used to determine the optimal concentrations of medium. Subsequently, we applied the artificial neural network-genetic algorithm optimization method, which significantly increased the viable bacterial count. Fermentation kinetics were modeled using logistic growth and Luedeking-Piret models, which accurately predicted cell growth. Amberlite IRA 67, an anion exchange resin, effectively adsorbed lactic acid and maintained pH levels. Furthermore, the combined use of fed-batch fermentation and ion exchange alleviated the effects of acid inhibition, salt stress, and substrate limitation, resulting in a maximum cell density of 10.01 lg CFU/mL, a 9.3-fold increase over the basal medium. This study develops a robust and cost-effective strategy for the industrial production of TCS, significantly optimizing probiotic production processes.IMPORTANCE TCS possesses outstanding aromatic characteristics, making it suitable for producing fermented dairy products. The goal of cultivating TCS at high density is to increase production yields, overcome challenges related to acid inhibition, and optimize fermentation processes. This study employed an artificial neural network (ANN) and genetic algorithms (GA) to determine the ideal composition of the proliferation medium for TCS. It constructed a dynamic model to track bacterial growth, product formation, and substrate consumption during fermentation, analyzing the process's dynamic patterns. Furthermore, by utilizing resin adsorption and fed-batch cultivation techniques, the production of lactic acid as a by-product was effectively minimized. This approach enabled to multiply rapidly to high concentrations, laying a foundation for the industrial production of high-yield aroma starters. This advancement supports the bacterium's application in various sectors, including dairy processing and functional food production.