Synthesis of AI-2 in vitro and effect of AI-2 on bacteriocin synthesis of Lactobacillus plantarum KLDS1.0391

The factors including incubation temperature,p H,enzyme concentration and incubation time were optimized by single- factor experiment design. Then AI- 2 was synthesized under the optimum conditions. The biological activity of the synthesized AI- 2 in vitro,was about 1- fold higher than the positive control. In order to research effect of AI-2 on the growth and bacteriocin synthesis,Lactobacillus plantarum KLDS1.0391 was cultured in MRS broth supplemented with AI- 2 synthesized. The expression level of pln EF gene encoding bacteriocin of Lactobacillus plantarum KLDS1.0391 cultivated for 15 h was studied by RT-PCR.The results showed that the optimum conditions for the synthesis of AI-2 in vitro were determined as follows: the SAH concentration of 2 mmol / L,the Lux S protein concentration of 1.0 mg / m L,the Pfs protein concentration of 0.5 mg / m L,the incubation temperature of37 ℃,p H of 7.5,and the incubation time of 5 h.Growth rate of Lactobacillus plantarum had no significant change,and the inhibition zone against Bacillus subtilis ATCC6633 increased significantly after cultivated in the MRS broth supplemented with AI-2 synthesized for 3 h.And the expression level of pln EF gene of the experimental group was1.89- fold higher than the blank control.In this study,the conditions for the synthesis of AI-2 in vitro were optimized.AI- 2 played an obvious positive regulatory role on bacteriocin production,and the regulatory effect may be associated with the increases of transcriptional level of pln EF gene.