Screening And Characteristic Research Of Anti-yeast Lactic Acid Bactera

With the enhancement of food safety awareness of consumers, natural food with nochemical additives has become the trend in food consumption, which makes biopreservationthe hot issue of food safty study. Various researches have reported that lactic acid bacteria(LAB), which were generally recognized as safe (GRAS), showed antifungal activities andbecame the potential candidates of biopreservation.Forty-six Gram positive and catalase negative LAB were isolated from several traditionalfermented food in Sichuan by calcium-dissolving method. Several spoilage yeast indicatorssuch as Canidia albicans and Canidia. glabrata were used for the screening of anti-yeastLAB by the double-plate method and microtitre plate well assay. Cell-free culturesupertanents (CFSs) of the isolated LAB were collected and six of them showed anti-yeastactivities.According to physiological and biochemical tests, as well as16S rDNA sequencinganalysis, isolates AT6and AT22were identified as Weissella cibaria, isolates AT4, AT28andAT36were identified as Lactobacillus plantarum, isolate AT15was identified asEnterococcus faecium.The incubate condition of Weissella cibaria AT6which showed superior anti-yeast effectwas optimized by the response surface method based on the result of single factorexperiments. The result showed that the incubate temperature, time and initial pH of themedia had the greatest significant influence on the inhibition activity. When incubation inMRS at34℃for40h with initial pH5.5, the CFS of AT6got the best inhibition rate at90.51±0.87%with16.36%improvement.Preliminary study on the inhibition properties of CFS AT6suggested that the inhibitoryactivity was supplied by the synergy effect of several antifungal factors. The bioactivity ofCFS AT6was significant influenced by the pH value. But CFS AT6presented higherinhibitory activity than the MRS broth in which the pH value had been adjusted with lacticacid or acetic acid separately. It showed non-significant difference after the treatment withprotelotytic enzymes. The concentration of phenyllactic acid which was detected by HPLCwas31.228±0.24μg/mL in the CFS of AT6. Four different cyclic dipetides, cyclo(Phe–Pro),cyclo(Gly-Pro), cyclo(Leu-Pro) and cyclo(Gly-Leu), were detected by GC-MS. As a result,the inhibition effect of AT6was due to the synthetic effect of the above compounds withantifungal property. Six LAB with inhibition effects on spoilage yeasts were isolated, among which, W.cibaria AT6showed superior inhibition rate with90.51%. This study provided the highlypromising candidates of novel preservatives or starters for food biopreservation.