Isolation, Identification Of Antifungal Lactic Acid Bacteria And Analysis Of Their Antimircrobial Substances

Along with people pay more attention to the food safety and their own status ofhealth. It has been one of the main trends to search a better antimircrobial substancewith broad-spectrum, highly effective and security as natural food antiseptic andbiopreservative in the food industry. Lactic acid bacteria produce a variety ofantimicrobial compounds, which have been reported the application and researchdevelopment of food preservation and food industry for decades.In this paper, six strains of lactic acid bacteria which have showed stronginhibitory activity against Aspergillus flavus were screened from a lot of experimentalmaterials. We used ammonium sulphate precipitation, HPLC and GC-MS analyticalmethod to identify the antimircrobial substances. Also studied the inhibition of moldsoccurred on the moldy corn kernels using the antimicrobial substances. These resultswere described as followes:1. Six strains with strong inhibitory activity against A. flavus were isolated by theoverlay method. These strains were identified by both phenotypical and physiologicaltest and the16S rRNA gene sequence analysis. The results indicated that these strainswere Lactobacillus pentosus strains.2. Six strains have broad-spectrum inhibitory activity against Gram-positivebacteria, Gram-negative bacteria and molds.3. After ammonium sulfate precipitation from the cell-free supernatant of strainM-1-1culture, antimircrobial tests showed that crude protein can inhibit againstMicrococcus tetragenus and Pseudomonas aeruginosa, but not against A. flavus.In the cell-free supernatant of culture, some antimircrobial substances includinglactic acid, acetic acid, succinic acid, citric acid, palmitic acid, oleic acid, stearic acidand linoleic acid were found by GC-MS and HPLC analysis. Designing mixed acid ascontrol materials have preliminarily determined that organic acid is the majorantimicrobial sustance produced by LAB.4.9strains of molds were isolated on the moldy corn kernels. Throughidentification of colony and morphology characteristics of the pure culture bacteria,there are one rhizopus strain, three mucor strains, one aspergillus strain, twopenicillium strains, one actinomucor strain and one Ustilago strain. 5. The inhibition of nine molds occurred on the moldy corn kernels was alsostudied use the antimicrobial substances produced by lactic acid bacteria. The resultsshowed strong inhibitory activity against six molds.