3‐phenyllactic acid production by free‐whole‐cells of Lactobacillus crustorum in batch and continuous fermentation systems

3-Phenyllactic acid (3-PLA) has been widely used in food and material industries. Three Lactobacillus crustorum strains have shown greater 3-PLA production ability in our previous study. The objectives of this study were to further improve 3-PLA yields in batch and continuous fermentation systems using of free-whole-cells of the three L. crustorum strains.The fermentation conditions of free-whole-cells of the three L. crustorum strains for 3-PLA production were optimized. Among these strains, L. crustorum NWAFU 1078 showed excellent reusability and significantly (P < 0·05) greater 3-PLA production ability than the other strains after 10th recycle. The strain possesses three l-lactate dehydrogenase and three d-lactate dehydrogenase catalysing 3-PLA production from phenylpyruvic acid (PPA). Under the optimal conditions, the strain produced 15·2 mmol l-1 3-PLA (76% PPA conversion rate) in a batch fermentation system and 6·5 mmol l-1 h-1 3-PLA (55% PPA conversion rate) in a continuous fermentation system using a 0·6 dilution rate.Free-whole-cells of L. crustorum NWAFU 1078 showed excellent reusability and higher 3-PLA yields under optimal biotransformation conditions in both batch and continuous fermentation systems.This study provides the possibility to use the free-whole-cells of L. crustorum NWAFU 1078 as a biocatalyst for effective production of 3-PLA.