Production of volatile phenols by kimchi Lactobacillus plantarum isolates and factors influencing their phenolic acid decarboxylase gene expression profiles

• Twelve percent (6/50) of kimchi isolates could decarboxylate hydroxycinnamic acid.
• Positive isolates were identified as Lactobacillus plantarum and possessed padA.
• padA expression was mostly significantly affected by p-coumaric acid concentration.
• The most significant factor affecting bacterial growth was pH of the medium.

Potential of kimchi lactic acid bacteria (LAB) isolates to produce volatile phenols and factors affecting their phenolic acid decarboxylase (padA) gene expression profiles were investigated in this study. Twelve percent (12%) of 50 tested LAB isolates were found to decarboxylate hydroxycinnamic acids. All six isolates were identified as Lactobacillus plantarum and possessed the padA gene. The highest padA expression was achieved on the third day of incubation with ferulic acid, with a relative expression of 3.30 ± 0.32. The effects of glucose, substrate, and product concentrations, and the pH of the medium were investigated using response surface methodology for the first time in this study. The expression profiles of the padA gene were diverse in various stress environments. The concentration of p-coumaric acid was the most significant factor being positively correlated with the expression levels of the padA gene, but other factors did not show any significant effects. High concentrations of substrates could confer antibacterial activity. Therefore, decarboxylation reaction was suggested as a bacterial response to overcome the antibacterial activity. The phenolic acid decarboxylase activities of L. plantarum isolates found in this study can provide insights for their potential application in the development of food-grade flavors and additives.