Kinetic characteristics of long-term repeated fed-batch (LtRFb)l-lactic acid fermentation by aBacillus coagulansstrain

Application of degradable plastics is the most critical solution to plastic pollution. As the precursor of biodegradable plastic PLA (polylactic acid), efficient production ofl-lactic acid is vital for the commercial replacement of traditional plastics.Bacillus coagulansH-2, a robust strain, was investigated for effective production ofl-lactic acid using long-term repeated fed-batch (LtRFb) fermentation. Kinetic characteristics ofl-lactic acid fermentation were analyzed by two models, showing that cell-growth coupled production gradually replaces cell-maintenance coupled production during fermentation. With the LtRFb strategy,l-lactic acid was produced at a high final concentration of 192.7 g/L, on average, and a yield of up to 93.0% during 20 batches of repeated fermentation within 487.5 h. Thus, strain H-2 can be used in the industrial production ofl-lactic acid with optimization based on kinetic modeling.