Isolation,Identification And Characterization Of Weissella Viridescens

Weissella viridescens is the most important species of Weissella in meat processing industry.It can cause spoilage of meat products,which has become a great threat to the quality and safety of meat products and led to a huge economic loss the meat industry.So far,little data have been reported on the growth characteristics and antimicrobial activity of W.viridescens.Therefore,the aims of our study were to investigate the isolation and identification of W.viridescens and its growth characteristics under environmental stimulation,estalish a rapid detection method for W.viridescens,and assess the antimicrobial activity and probiotics of W.viridescens.The main results from this study were as follows:?1?A total of 12 isolates were colleted from the spoiled low-temperature cooked beef by vacuum packaging and then subjected to phenotypic analysis,physiological and biochemical identification,and 16S rDNA sequence comparison analysis.Among these isolates,three were identified as W.viridescens.?2?Growth characteristics of W.viridescens under different conditions,including acid,salt,high temperature,and bile salt,as well as the susceptibility to disinfectants of W.viridescens were investigated in this study.Our results showed that W.viridescens was able to grow under pH 4.0 or 8%NaCl or 43?.Growth of W.viridescens was not significant inhibited when bile salt was added to the medium and the final concentration was 0.3%.Among the five commonly used disinfectants,only iodide with the conventional use concentration exhibited good antimicrobial effect against W.viridescens.?3?Conventional PCR and real-time PCR?qPCR?assay of W.viridescens were established using rpoA as target gene in this study.Both conventional PCR and qPCR methods described in our study were specific for W.viridescens.The sensitivity of qPCR was 100 times higher than that of conventional PCR.The limit of detection for qPCR was established in 2.67×10^-3 pg/PCR reaction for genomic DNA from W.viridescens.With regard to the bacterial culture and the artificially inoculated beef,the limit of detection was established in 30 CFU/mL and 0.8 CFU/g,respectively.Results of independent repeated test for samples with different concentrations showed standard deviation of CT less than 1 and coefficient of variation in the range of 0.02%¹.28%.qPCR method developed in this study can be considered to be a fast tool for detection of W.viridescens due to its specificity,sensitivity,reproducibility,and accurate quantification.?4?Supernatant of W.viridescens did not have antimicrobial effect on eight indicator strains,suggesting that W.viridescens in our study could not produce bacteriocin or it just produced bacteriocin with low concentration.Supernatant of W.viridescens inhibited the biofilm formation and motility of L.monocytogenes which is an important foodborne pathogen.Results demonstrated that W.viridescens had the capacity to eliminate the cholesterol in medium.Moreover,better eliminating effect was observed with increasing time of incubate.When the medium contained 15?g/ml of cholesterol,highest eliminating rate of cholesterol with 82.4%was observed after incubating for 72 h.In conclusion,W.viridescens was tolerant to various environmental stimuli,including acid,salt,high temperature,and bile salt.qPCR method developed in this study can be considered to be a fast and accurate tool for detection of W.viridescens.Supernatant of W.viridescens inhibited the biofilm formation and motility of L.monocytogenes.W.viridescens had the ability to eliminate the cholesterol in medium.