Effect of Lactiplantibacillus plantarum cell-free supernatant on the physiology, quorum sensing, transcription, and enhanced GABA production of Enterococcus faecium

A co-culture strategy has been proposed for the production of desired products. However, the interaction effect on enhancing γ-aminobutyric acid (GABA) production requires further investigation. In this study, the mechanism by which Lactiplantibacillus plantarum BC112 cell-free supernatant (CFS) enhances GABA production in Enterococcus faecium AB157 was investigated, including physiological characteristics, quorum sensing (QS), and mRNA expression. The results showed CFS can significantly enhance the production of γ-aminobutyric acid (GABA) in E. faecium AB157, with a maximum increase of 4.6 times compared to the strain without CFS. CFS promoted the growth of E. faecium AB157, enhanced the activity of glutamate decarboxylase (GAD) and ATPase, and reduced the pH. The effect of CFS on QS was demonstrated through changes in Autoinducer-2 (AI-2) activity and luxS expression. Moreover, 16 amino acids were detected in CFS, with glutamic acid having the highest content. Additionally, 974 genes of E. faecium AB157 differed significantly in cultures with added CFS, which involved glycolytic, amino acid, and GABA biosynthetic pathways. Therefore, Lb. plantarum BC112 CFS enhances GABA production in E. faecium AB157 by affecting energy metabolism, the QS system, and the GABA biosynthesis system.