The Effect Of Bacillus Subtilis On The Bacteriocin Production And LuxS Gene Expression Of Lactobacillus Paracasei

Lactobacillus paracasei HD1.7 was isolated from the Chinese sauerkraut fermentation broth which contained a kind of bacteriocin Paracinl.7.Due to its broad antibacterial spectrum,Paracin1.7 would become the novel food preservative with a profound research value.The research aimed at investigating the relationship between the Lactobacillus paracasei and Bacillus subtilis by the method of coculture.Whether Bacillus subtilis would promote the production of Paracinl.7 was explored in the research through coculturing strain HD 1.7 with cells and supernatant of Bacillus subtilis culture respectively.Meanwhile,QRT-PCR was utilized to detect the expression of LuxS gene in the condition of coculturing Lactobacillus paracasei strain HD 1.7 with cells and supernatant of Bacillus subtilis culture.Finally,the research revealed the relationship between production of Paracinl.7 and quorum sensing.The studies of Lactobacillus paracasei strain HD 1.7 would inhibit the growth of Bacillus subtilis and the Bacillus subtilis would improve the production of Paracinl.7 of the strain HD1.7 were groped by cocultured the two strains.The results showed that the supernatant of strain HD 1.7 culture could inhibit the growth of Bacillus subtilis.The growth phase of Bacillus subtilis was prolonged and the growth rate of it was slowed after adding the supernatant of strain HD1.7 culture whose cell density was 106 CFU/mL and 107CFU/mL.And then,it could absolute inhibit the growth of Bacillus subtilis when the cell density of strain HD 1.7 reached 108 CFU/mL and 109 CFU/mL.The results revealed that both cells and supernatant of Bacillus subtilis culture could promote the expression of LuxS gene in the Lactobacillus paracasei.While the supernatant of Bacillus subtilis culture exerted more significant effect on the expression of LuxS gene,which implied that the main signals stimulating factor presented in the fermentation supernatant of Bacillus subtilis.Further study indicated that crude proteins of supernatant of Bacillus subtilis culture could promote the production of Paracin1.7 of strain HD 1.7 reached a threshold after precipitated with 60%saturation degree ammonium sulfate and purified by CM Sepharose Fast Flow.The potency of Paracinl.7 was 101.68±1.76 AU/mL.We further confirmed Bacillus subtilis could produce some materials as a kind of signal molecule which could promote the production of Paracinl.7.This reseach not only laid a foundation for the quorum sensing of the strain HD 1.7 and riched the contents of this theory,but also improved the production of Paracinl.7 which would widely used in food and medicine industry.