The Isolation,Identification And Probiotic Properties Of Lactic Acid Bacteria From Sauerkraut

The experiment selected the traditional craft natural fermented pickled cabbages of Northeast China as the research objects.Lactic acid bacteria(LAB)was isolated from the pickled cabbage and identificated preliminarily.Then screened out of strains of good probiotic properties for researched and studied the function and fermentation characteristics of them.The main conclusions are as follows:The 72 LAB strains were isolated from the 10 samples of pickle cabbages collected in the surrounding area of Qiqihaer.Comparing of colony phenotype and gram reaction,34 LAB strains were selected for RAPD analysis.The 21 LAB strains were selected by gel imaging of four primers electrophoresis for 16 rRNA gene sequencing analysis.The results showed that 16 strains were Lactobacillus and 5 strains were Enterococcus.Screening from the 21 LAB strains and 5 LAB strains were obtained which had a good performance of acids and bile salt resistance.Screening out of 5 LAB strains in pH 3.0 condition effected of 2h and MRS medium with 0.3% bile salt environment 2h,got higher survival rates.Among them,strain 53 was non-hydrophobic and the hydrophobicity rate was 16.0%;Strain 8,32,56,59 were highly hydrophobic and strain 56 was the most hydrophobic with a hydrophobicity rate as high as 82.0%.The antibiotic sensitivity of 5 strains to 7 kinds of antibiotics was tested by the Kirby-Bauer disc diffusion method.The result showed that all the strains tested were resistant to gentamicin,streptomycin and sensitive to tetracycline,doxycycline;The strain 8 was resistant to vancomycin,however the other 4 strains were sensitive to it;Among 5 tested strains,strain 32 was intermediate to cephalexin and the other 4 strains were resistant to it.The antioxidant activity of 5 LAB strains intact cell suspension and cell-free extract was researched through determinations of reducing power and scavenging hydroxyl free radical and scavenging DPPH free radical.The results showed that 5 LAB strains had different antioxidant activity,the reducing power,hydroxyl free radical scavenging and DPPH free radical scavenging ability of intact cell suspension were higher than those of cell-free extract.The reducing power of strain 56 was relatively high,the hydroxyl free radical scavenging and the DPPH free radical scavenging ability of strain 59 were relatively high,reaching 39.3% and 39.3% respectively.5 LAB strains with anti-bacterial activity to Staphylococcus aureus and Escherichia coli were tested by the method of Oxford cup.The results showed that only strain 56 had inhibitory effect on the growth of Staphylococcus aureus,and the other 4 strains had no inhibitory effect.Strain 32,53 and 56 had inhibitory effects on the growth of Escherichia coli,and strain 53 was the strongest with an inhibition zone as high as 19.17 mm.Through the similarity comparison analysis of 5 Lactobacillus strains' housekeeping gene – RNA polymerase ? subunit(rpoA)and the phenylalanyl-tRNA synthase gene(pheS),I found that the strain 8 was Enterococcus lactis,the strain 32 and 53 were Lactobacillus paracasei subsp.paracasei,the strain 56 was Lactobacillus paraplantarum and the strain 59 was Lactobacillus plantarum subsp.plantarum.By testing the 5 strains of lactic acid bacteria's growth curve and the ability to produce acid,I found that the 5 strains of bacteria grew slowly in 1-4h,then entered logarithmic growth stage after 4h and the growth rate was accelerated,and then entered the stable period after 12-14 h.Among the 5 strains of bacteria,the vitality of strain 8 was the weakest,the vitality of strain 32 was the strongest,and the other three strains had little difference in the vitality.The pH value of 5 strains of lactic acid bacteria changed little during the period of 0-4h,the pH changed rapidly during the period of 4-14 h,the pH value changed gradually after 14 h and the strains entered into the stable period.