Screening and identification of lactic acid bacteria with antagonistic activity against Aeromonas sobria from traditional fermented vegetables

Objective: To screen lactic acid bacteria( LAB) with strong antagonistic activity against Aeromonas sobria from traditional fermented vegetables.Methods: Cell- free supernatants( CFS) from LAB with inhibitory activity against A. sobria was screened using the double agar diffusion methods. The strain was identified by biochemical tests and 16 S rRNA sequence analysis.The antibacterial substance was analyzed using protease sensitivity test,acid test and heat- treated test.The integrity of cell structure was observed by scanning electron microscope. Results: Strain LZH2- 5 with outstanding antagonistic activity against A.sobria( 10~6 CFU / m L) was screened from pickled cucumbers,and it was identified as Lactobacillus plantarum. The antagonistic activity of cell- free supernatants produced by strain LZH2- 5 was lost 29.38%,23.93%,22.30%,19.47% and14.59% by treating with trypsin,papain,neutral protease,alkaline protease and pepsin respectively.The antibacterial activity of CFS was stable after thermal treatment with 40,60,80 ℃ for 30 min,and decreased 16.66% and 25.40% after incubation at100 ℃ and 121 ℃ for 30 min,respectively,and was effective within p H3.0 ~ 4.0. The MIC of inhibitory substance was12.0 mg / m L. The scanning electron microscope images revealed that the integrity of cell of A.sobria treated with LZH2-5 CFS was damaged and dissolving. Conclusion: Lb. plantarum LZH2- 5 with strong inhibitory activity against A. sobria was screened from pickled cucumbers.The antibacterial substance produced by strain LZH2-5 was preliminarily determined as bacteriocins.It can be used as the antagonism original strain for the control A.sobria in aquaculture.