Chemical Composition And Biodiversity Of Lactic Acid Bacteria Of Koumiss-A Traditional Fermented Mare Milk Product In Xinjiang Of China

In the present study, the chemical composition and microorganism flora of the Koumiss, a traditional fermented mare milk product in Xinjiang of China, were analyzed. The biodiversity and DNA polymorphism of lactic acid bacteria (LAB) involved in Kourniss were also investigated. The results provides the basic data for systematically understanding the characteristics of Koumiss in Xinjiang, and gives useful information for further exploitation and utilization of lactic acid bacteria in traditional fermented milk products. At the same time, the premiliminary experimental procedure of AFLP has been established to classify Lactobacillus strains at the gene level.The chemical composition and microorganism flora of the 28 Koumiss samples obtained from different areas of Xinjiang were analyzed. The results indicated that the mean contents of fat, protein, lactose, ash, calcium and phosphorus of 28 samples were (1.87±0.33)g/100mL, (2.07±0.29)g/100mL, (2.69±0.63)g/100mL, (0.28±0.05)g/100mL, (72.25±13.46) rag/100mL, (52.23±11.35)mg/100mL, respectively. The pH values averaged at 3.89±0.27, acidity aligned at (106.57±43.21)°T, lactic acid leveled at(9.10±3.56)g/L, acetic acid (1.18±0.50)g/L, citric acid (0.06±0.06)g/L and ethanol (14.52±3.79)g/L. For most of the samples, the counts of lactic acid bacteria and yeasts are ranged from 1.07×10~7 cfu/mL to 9.70×10~7cfu/mL and 10~5 cfu/mL to 10~6 cfu/mL, respectively. Generally, in these Koumiss samples, the counts of the lactic bacteria were higher than those of the yeasts by one or two logarithm.A total of 152 strains of LAB were isolated from 28 home-made Koumiss samples. They were identified using standard conventional identification methods. The predominant strains proved to be mainly Lactobacillus(L. ) helveticus (51.3% of the total isolates), L. acidophilus (18.4%) and L. easel subsp, pseudoplantarum(8.6%), while strains of L. gasseri, L. casei subsp, casei, L. sanfrancisco, L. coryniformis subsp. coryniformis, L. curvatus; L. brevis, L. ruminis, L. plantrum, L. homohiochii, L. fermentum, L. dellbrueckii subsp, buIgaricus, L. crispatus, L. farciminis and L. hilgardii were also present at lower numbers(1～4strains). 8 strains of the isolates can't be identified according to present methods. The species and amount of LAB in Koumiss from different areas of Xinjiang were different, but L helveticus and L. acidophilus exist in all Koumiss samples and L. helveticus was the predominant strain. Most of the strains ( 69.1% ) could grow at the media of pH 3.5.8 strains of LactobaciIlus that could not be identified using standard conventional identification methods were further identified by 16S～23S rDNA short intergenie spacer region sequence comparisons. Results indicated that XF5-2 belonged to L. casei subsp. casei. B10-2 and XB2-3 were identified as L. helveticus. E91 and E112 were L. kefir. C56, D73 and E96 were classified temporarily as L. ferintoshensis. The method of 16S～23S rDNA short intergenic spacer region sequence comparison had the advantage to distinguish L. rhamnosus and L. easel strains. This method could not differentiate L. ferintoshensis, L. kefir, L. buchneri and L. hilgardii clearly, but it was helpful to group those unidentified isolateds to this group.The DNA polymorphism of 67 strains of Lactobacillus, which were isolated from Koumiss in Xinjiang, were analyzed using AFLP marking technology. The interspecific grouping results indicated that all of the 67 strains of Lactobacillus were grouped to 18 AFLP groups at the similarity of 73%. L. casei,L. acidophilus and L. helveticus could be discriminated on the basis of AFLP patterns. As for L. helveticus, the results by AFLP was consistent with that of the results by standard conventional identification methods. The DNA polymorphism of lactocabiUi also indicated that there was a high similarity among L. curvatus, L. sanfrancisco, L. coryniformis subsp, coryniformi, L. hilgardii, L. fermentum, L. ruminis, L. crispatus and L. brevis. All of them were grouped in the same AFLP group with 8 strains of L. casei. The gene types of L. easel,L. acidophilus and L. helveticus were also analyzed. They were elassfied to 8, 12 and 9 AFLP gene types respectively at the similarity of 73%. Results from this study showed that there was no positive relationship between the AFLP gene types and the origin of the strains.