Identification And Application Of Yeasts Isolated From Koumiss And Yak Milk Dreg Collected In The Western China

Microbial resources have the unique ecological and economic significance, and its exploitation and utilization has become one of the hot spots in the field of modern applied biology. The Western pastoral area is one of the major dairy livestock areas in China, which contains an extremely rich microbial resources, and considered as an important treasure of biological resources. In this study, the typical products such as koumiss and yak milk dreg in Western Pastoral Areas were conducted. The advantage microbial resources and its application characteristics were studied, and provided technical support for the effective development and utilization of microbial resources. The main conclusions were as follows:(1) The population of yeast in koumiss was from 105 CFU/mL to 107 CFU/mL, the lactobacillus number was between 104 CFU/mL and 107 CFU/mL. The number of yeast strains in seven sampling points was 105 CFU/mL, and the remaining three were slightly higher, and the number of yeast strains was fluctuated between 106 CFU/mL to 107 CFU/mL. From the view of sampling points, the live bacteria number in Inner Mongolia was 105 CFU/ml, and the samples had no significant difference(P > 0.05). The number of lactic acid bacteria in Xinjiang samples was 105 CFU / ml, while the yeast number was mainly between 106 CFU/ml to 107 CFU/ml, and the difference was significant(P < 0.05).(2) The yeast strains isolated from Xinjiang and Inner Mongolia koumiss samples were identified as 7 genera and 13 species. Kluyveromyces marxianus,Pichia cactophila,Pichia fermentans,Saccharomyces cerevisiae,Candida zeylanoides,Cryptococcus albidus were the most common culturable species. The type and quantity of yeast strains in different regions presented diversity. The dominant yeast strains in Inner Mongolia were Kluyveromyces marxianus, Pichia cactophila and Pichia fermentans. The dominant yeast strains in Xinjiang were Candida zeylanoides and Kluyveromyces marxianus.(3) The biological and fermentation characteristics of yeast strains isolated from koumiss(60 isolates) and yak milk dreg(91 isolates) were studied. Results were as follows:(1) Eight yeast strains had the strong ability to produce protease and the enzyme activity was between 1264.4 U/mL to 1367 U/ml. There were sixteen strains could produce lipase and the enzyme activity was between 32.48 U/mL to 138.01 U/mL.(2) R. dairenensis and S. crataegensis had lower sensitivity to the natamycin, and the sensitivity of P. fermentans and P. cactophila was higher.(3) Acid production characteristics of yeasts were different. One of the best was B1-2, up to 103 oT.(4) The ethanol yield of strains was between 1.62 g/L to 2.13 g/L. Different species showed different ethanol production capacity. And the same yeast species isolated from the different regions also showed different fermentation characteristics.(4) According to the biological characteristics and fermentation characteristics of the yeasts, four strains of good fermentation were screened to the dairy products, two of them were Pichia cactophila, and the remaining two strains were Kluyveromyces marxianus and Candida zeylanoides respectively. Five strains with good characteristics were selected to the production of pawpaw wine, all of them were Saccharomyces cerevisiae.