Chemical And Microbiological Compositions And Isolation,Screening And Indentification Of Lactic Acid Bacterium From Fermented Milk In Tibet

In the present study, The chemical and microbiological compositions of fermented milk samples in Tibet were analyzed .fifty-three strains of Lactobacillus were isolated from these samples.Moreover,traditional Physiological methods were used to identify and screen the species of these Lactobacillus.The average content values of various indexes tested in ten samples were described as follows. Protein,soluble sugar,Fat,dry-matter and ash were (4.79±0.03)%,(1.58±0.04) %,(6.65±0.05)% and(17.01±0.35)%,(5.54±0.27)%.Calcium and phosphorus were(144.85±2.14)mg/100g and (118.52±0.82) mg/100g. The average contents of K,Na,Mg,Fe,Cu,Mn and Zn of the 10 samples were (84.59±2.16)mg/100g,(78.30±1.73)mg/100g,(14.96±0.70)mg/100g,(25.68±0.59)mg/100g,(2.07±0.06)mg/100g,(2.68±0.05)mg/100g,(6.83±0.06)mg/100g。For most of the twenty-nine samples,the counts of lactic acid bacteria and yeasts are ranged from 1.10×106 CFU/g to 6.78×107 CFU/g and 1.52×105 CFU/g to 4.65×106 CFU/g,respectively,Generally,in these samples,the counts of the lactic acid bacteria were higher than those of the yeasts by one or two logarithm.A total of 61 strains of LAB were isolated from 31 samples.Among of 61 strains,53 strains were Lactobacillus(86.9%of the total isolates),8 strains were cocci(13.1%of the total isolates). Among of 53 strains Lactobacillus, L.delbrueckii subsp.lactis(13 strains), L.buchneri(7 strains), L.acidophilus and L.casei(5 strains of each), L.curvatus(4 strains) ,L.kefirgranum,L.sake,L.hilgardii and L.fermentum(2 strains of each), L.delbrueckii subsp. bulgaricus,L.amylophilus,L.helvericus,L.coryniformis subsp.torquens,L.fructosus and L.parakefir(1 strains of each).5 strains of the isolates can not be identified according to present methods. L.delbrueckii subsp.lactis(21.3 % of the total isolates) and L.buchneri(11.7%of the total isolates) were the predominant strains.LS7-2(L.acidophilus),SN2-1(L.curvatus)and NQ2-1(L.curvatus) could grow at the media of pH 3.0,accelerate to produce acid and strong ability of acid production.