The β-galactosidase LacLM plays the major role in lactose utilization of Lactiplantibacillus plantarum

Abstract Lactiplantibacillus plantarum has often been used for fermentation of lactose-rich substrates. However, its growth in lactose has not been studied at the molecular level and the role of different β-galactosidases is also unknown. In this study, transcriptome sequencing was performed to reveal the difference of gene expression when Lp. plantarum LP01 was cultivated in glucose and lactose medium. Two genetic loci involved in lactose metabolism were highly transcripted by lactose induction, in which β-galactosidase coding gene lacA, lacL and lacM were up-regulated by 9.86, 9.12 and 9.53-fold, respectively. To explore the detail role of different β-galactosidase, mutant strains Lp. plantarum ΔlacA, Lp. plantarum ΔlacLM and Lp. Plantarum ΔlacAΔlacLM was constructed by gene knockout. Results showed that the growth of Lp. plantarum ΔlacA was slightly weakened in lactose medium, while the growth of Lp. plantarum ΔlacLM and Lp. plantarum ΔlacAΔlacLM was completely inhibited. Furthermore, the growth of Lp. plantarum ΔlacLM could be restored after transformed into an complementation vector pNZ8148-PlacLM-lacLM. Therefore, the β-galactosidase LacLM plays the major role in lactose utilization of Lp. plantarum, providing a theoretical foundation for the growth and metabolism of Lp. plantarum in lactose medium.