Diversity of Bacteria Producing Milk-clotting Enzymes in Qinghai Pastoral Area

To excavate fine milk-clothing enzyme producing strains and develop new type of milk-clothing enzyme from bacterial sources. Microorganisms with high milk-clotting activity from soil samples collecting form Qinhai pastoral area in Tibetan Plateau of China was isolated and screened. Strains isolated were identified by the 16S rRNA sequence similarity and the diversity was analyzed by the phyologentic tree. Results showed that a total of 21 bacterial strains producing milk-clotting enzymes were isolated from 36 soil samples. The ratio of deposition zone to the colony diameter among the isolated strains in the casein plate medium ranged from 1.41 to 5.5.Media affected the milk-clotting activity and proteolysis activitiy of bacteria obviously. Milk-clotting activity among the isolated strains ranged from 11.3 to 1215.6 SU/mL in wheat bran juice medium,and proteolysis activitiy was between 14.6 and 59.5 SU/mL. Out of 21 strains,there were 14 strains found to be in the genus of Bacillus,implying that Bacillus was the most dominant genus of bacteria producing milk-clotting enzymes. The analysis indicated that the diversity of bacteria producing milk-clotting enzymes in Qinhai pastoral area was high.