Identification Of Lactobacillus Plantarum ZJQ And Study On Plantaring ZJQ

Because synthetic preservatives and antibiotics are widely used in prenatal and postnatal aspects of agricultural products which caused a series of food safety issues, people start looking for safe natural preservatives and antibacterial agents. The bacteriocin from lactic acid bacteria for its excellent antibacterial and from the food-grade micro-organism, has got more and more attention.In this study, a bacteriocin-producing strain was isolated from infant feces. It revealed that the strain showed homology to Lactobacillus plantarum by basic characteristic. And 16S rDNA analysis showed that its 16S rDNA showed 99.4%homology to Lactobacillus plantarum strain AF1 in its 16S rDNA sequence. So we named this strain as Lactobacillus plantarum ZJQ and the bacteriocin as plantaricin ZJQ. Lactobacillus plantarum ZJQ was produced mainly during exponential phase and ceased at stationary phase. Like most of other bacteriocins produced by LAB, plantaricin ZJQ was stable to heat under low pH and labile under high pH. It can retain 80%Of the activity after 30 min of 100℃heating, when the pH value was above 4.0 plantaricin ZJQ would lost its activity. Plantaricin ZJQ was inactivated by trypsin and proteinase K. Plantaricin ZJQ showed a broad range-of inhibitory spectrum, it can inhibit majority of test Gram-negative bacteria, and some test Gram-positive bacteria, such as Pseudomonas putida, Bacillus subtilis, Micrococcus luteus, Shigella flexneri, Staphylococcus citreus, Escherichia Coli, Salmonella and so on, but did not inhibited the growth of their own. By changing the fermentation medium and fermentation conditions to optimize the growth of Lactobacillus plantanim ZJQ and production of plantaricin ZJQ,we found that the best growing conditions and optimal production conditions were basically the same. Single factor experiments and response surface method revealed that the best composition of medium for glucose 2%, peptone 1%, concentrated yeast extract 1%, sodium dihydrogen phosphate 0.2%, sodium acetate 0.5%,3 rubber ammonium lemon acid 0.2%, sodium chloride 0.2%,0.1%Tween 80 at the optimal fermentation conditions of 30℃,60 mL/250 mL, the initial pH value of 6.5 when the highest activity, was up to the original two-fold. Using ammonium sulfate fractionation method to extract plantaricin ZJQ from the fermentation broth, going through dialysis desalting, concentration, bacteriocin was eventually used Tricine-SDS-PAGE electrophoresis to determine the molecular weight. It was of about 5 KDa weight.