Isolation And Identification Of Lactic Acid Producing Bacteria And Culture Conditions

The aim of this project was to screen lactobacillus strains of producing bacteriocin. Fermentation conditions of bacteriocin were studied in order to enhance the titer of bacteriocin and the biological features of coarse bacteriocin were also determined.Eight bacteriocin-producing lactic acid bacteria strains were screened from Chinese sauerkraut juice, which named as HDRS1-HDRS8. According to the morphological features, physiological and biochemical features, API identification kit and 16S rDNA sequence analyse of the strains, strains HDRS1-HDRS7 were identified as Lactobacillus plantarum and HDRS8 was identified as Lactobacillus brevis.The supernatant of HDRS1 and HDRS8 could strongly inhibit indicator strains after excluded inhibitive effect of H₂O₂ and organic acid, but the inhibitive activity decreased sharply after treatment with trypsin and proteinase K. The results confirmed that the anti-bacteria product produced by HDRSl and HDRS8 were both protein, which could be classed as bacteriocin.Different factors were investigated such as the ingredients of medium, temperature, pH, inoculating amount and medium capacity on production of bacteriocin in order to optimize the fermentation condition. The optimum carbon source of HDRS1 and HDRS8 were sucrose and glucose, respectively, and the optimal concentration were both 2%; the optimum nitrogen source and growth factor of them were beef extract and Tween80, respectively, and the optimal concentration was 2.5% and 0.1%, by orthogonal experiment. The optimum initial pH for HDRS1 and HDRS8 was 6.5 and they produced the highest amount of bacteriocin at 30℃ and 37℃, respectively. The optimum amount in one flask of HDRS1 and HDRS8 were 80mL/100mL and...