In this study, we explored the lactic acid production from molasses through a repeated-batch fermentation process using dynamic simulation. Our investigation revealed that sugar concentrations ranging from 50 to 150 g/l significantly impacted the dynamic profiles of sugar consumption concentration, microbial Enterococcus faecalis RKY1 growth, and lactic acid production. Through dynamic simulation, we identified the optimal inlet sugar concentration as 68 g/l (equivalent to 130 g/l molasses), resulting in a lactic acid average productivity of 3.9 g/l h (3-repeated batch). The simulation demonstrated the viability of a sustainable lactic acid production process using Enterococcus faecalis RKY1, enabling the repeated-batch fermentation process for multiple cycles. Comparative analysis with continuous fermentation indicated that repeated-batch fermentation offers a superior alternative, characterized by higher substrate conversion to lactic acid. This study contributes valuable insights into optimizing lactic acid production processes, emphasizing the efficiency and sustainability of the repeated-batch fermentation approach.