Phenyllactic acid: A green compound for food biopreservation

Consumer demand for minimally processed foods continues to increase every day, primarily due to a hike in consumer awareness on food and nutritional security. Chemical preservatives are increasingly becoming ineffective in exterminating microorganisms in food. On the other hand, the potential health risks associated with the chemical preservatives coupled with their regulatory restrictions call for novel and effective antimicrobials originated from safe sources. Therefore, food biopreservation using controlled microbes such as lactic acid bacteria (LAB) or their metabolites has been reviewed as a safer alternative for conventional food processing. Lactic bacterial antagonism against spoilage microbes and pathogens has been correlated with the production of various antimicrobial substances. Among them, phenyllactic acid (PLA) is an important broad-spectrum antimicrobial compound that inhibits the growth of undesirable microbes through multifaceted actions. PLA is a phenolic acid synthesized during phenylalanine and central carbon metabolism of LAB. Although chemical methods of PLA production have been well studied, few limitations such as complex technology routes and high impurities have hampered the PLA synthesis through chemical methods. Alternatively, PLA production using LAB as a whole-cell catalyst remains a feasible and eco-friendly method. In this context, the present review comprehensively recapitulates PLA biosynthetic pathways in the LAB and the methods to enhance the PLA yield through biotechnological and non-biotechnological strategies. Insights into the mechanism of PLA-associated microbial inhibition and anti-virulence actions have been deepened. Various possible food and feed applications of PLA or PLA producing LAB have been summarized. Finally, the regulatory and toxicological status of PLA has been highlighted. Overall, the present review offers factual information on LAB-derived PLA and provides future directions to the researchers to fulfill the existing research gaps.