Enhanced phenyllactic acid production from grass carp viscera hydrolysate using engineered Pediococcus acidilactici

This study aims to improve the yield of phenyllactic acid (PLA) in lactic acid bacteria (LAB). An aromatic amino acid transaminase gene araT and a l-lactate dehydrogenase gene ldhL from Pediococcus acidilactici La52 were cloned and employed to construct two plasmid-based expression strains (La52/pMG36e-araT and La52/pMG36e-ldhL) and three chromosomal integration expression strains (La52T, La52L and La52TL). Quantitative analysis revealed that overexpression of araT and ldhL significantly promoted PLA biosynthesis, whereby La52/pMG36e-araT and La52TL produced 839.19 ± 3.63 and 616.62 ± 4.48 mg/L PLA in modified MRS medium, representing 52.27 % and 11.56 % increases over their corresponding parental strains La52/pMG36e (551.11 ± 8.44) and La52 (552.70 ± 8.77), respectively. In grass carp viscera hydrolysate-based G2EH medium, La52TL showed 24.94 % higher PLA production than La52 (202.15 ± 3.85). After further optimization of the medium and fermentation conditions using response surface methodology, the PLA yield of La52TL markedly increased from 252.57 ± 6.65 to 337.86 ± 3.37 mg/L. Overall, this work significantly enhanced PLA production in LAB and proposed a promising route to valorize fish processing by-products.