Isolation, Screening And Identification Of Lactic Acid Bacterium From Traditional Fermented Milks In Ganzi Region Of Gansu

The function of fermented milk is due to lactic acid bacteria. The domestic and overseasresearchers are taking a lot of energy and time on isolation, screening super lactic acid bacteriafrom nature and the traditional fermented milk. The Ganzi region of Gansu province has veryspecial geographical and ecological circumstance: high altitude, low tempreture, changes intemperature from day to night. The resident of this region make fermented milks in immemorialmethods, which is simple but has long histoty. The fermented milks have good flavor, taste,exquisite structure, and keep flavor and structure on long time and natural tempreture.The content of this study is to research this resource of lactic acid bacterium, isolate, sreen,identified lactic acid bacteria from the traditional fermented milks and study the best fermentedcondition.In this study, 55 strains lactic acid bacteria were isolated from 14 samples of fermented milkscollected from the herdsmen's home in Ganzi region of Gansu. There were 30 strains Lactobacillusand 25 strains Lactococcus in these 55 strains lactic acid bacteria.The pure lactic acid bacteria strains are important in the production of fermneted milks.inlactic acid fermentation, which can produce acid and flavor of fermented milks. After selecting byfirst grade: Transferring of culture, coagulate time, Acidity, texture, flavor .8 strains were obtainedfor second selection: Souring rate in fermentation, Souring rate stored at 4℃Capability of produceacetaldehyde, Capability of produce diacetyl, Lively bacterium number stored at 4℃, Capability ofendure acid, Capability of endure cattle gallbladder salt, inhibitory activity. Finally, selecting 2strains Lactobacillus, 2 strains Lactococcus may be used as the starter culture of yogurt. 2 strains ofLactobacillus are C1 and M1 which have high sense organ appraisal, quick souring rate, shortcoagulate time, high production of acetaldehyde, good tastes, high lively bacterium number storedat 4℃, relatively capability of endure acid, capability of endure cattle gallbladder salt andinhibitory activity. 2 strains Lactococcus are I3 and H4 which have high sense organ appraisal, highviscidity, high stand against souring rate stored at 4℃, high lively bacterium number stored at 4℃.I3 is especially good at capability of endure acid, capability of endure cattle bile salt and inhibitoryactivity.The screeing strains of C1, M1, I3, H4 were identified by SHERLOCK(?) MicrobialIdentification System. The identifiable results are: C1 is Lactobacillus casei; M1 is Lactobacillus bifermentans; I3 is Enterococcus durans, H4 is Pediococcus acidilacticii.Finally, with the screen index: coagulate time, Acidity, texture, flavor and sense organ ofproduct, the optimum compound strains breed fermentation of yogurt: M1 and H4.The optimumfermented condition is leaven M1:H4 is 1:1; seed volume 3%, temperature 37℃, adding suger 7%。...