A new approach for efficient synthesis of phenyllactic acid from L-phenylalanine: Pathway design and cofactor engineering

Phenyllactic acid (PLA), a novel biological antiseptic agent with broad and effective antimicrobial activity, finds wide applications in the food processing field. In this work, a new approach for biocatalytic synthesis of PLA from l-phenylalanine (Phe) was constructed. First, selection of l-lactate dehydrogenase (LDH) was done to achieve the efficient synthesis of PLA from phenylpyruvic acid (PPA); Second, l-amino acid deaminase (l-AAD) and LDH were co-expressed to achieve the synthesis of PLA from Phe; Finally, formate dehydrogenase (FDH) was overexpressed to accelerate the regeneration of cofactor NADH from NAD, which is necessary for the biocatalysis of LDH. By this biocatalytic system, 30 g·L−1 Phe was transformed into PLA with 100% conversion ratio in 12 hr. This work developed a new and efficient biocatalytic approach for PLA production with Phe as a cheap substrate, which provides an alternative for PLA production in a green manner. Practical applications PLA is a novel antimicrobial compound with broad inhibition activity and has less side-effect on the health of human being. It is an ideal antiseptic that has received much attention in the food industry, for the control of microbial contaminants. In addition, PLA can be used as feed additives to replace antibiotics in livestock feeds. The newly established biosynthetic system in this work may be a promising technique for the industrial production of PLA due to high production and high efficiency.