Abstract:

This study examined the species diversity of lactic acid bacteria from Chinese yak milk cheeses and their
fermentation performance. Totally 17 samples were collected from Tibet, Yunnan and Xinjiang province, colony
enumeration with MRS agar plate and pH were tested to obtain basic information of samples. Lactic acid bacteria were
isolated and investigated by phenotypic and genotypic methods. Phenotypic analysis included morphology, physiological
and biochemical characteristics, carbohydrate fermentation pattern. Genotypic analysis included 16S rRNA sequencing
and species specific PCR. The technological characterization included acid-producing capability, citrate utilization,
proteinase and exopolysaccharide. The average colony enumeration of 17 samples was 4.08±0.60 (lg(CFU/g)), average pH was
4.52 ±0.29. A total of 39 strains were isolated and identified, 35 strains were Lactobacilli including L. buchneri
(2), L. casei (16), L. diolivorans (3), L. fermentum (3), L. helveticus (3), L. kefiri (3) and L. plantarum (5), 4 strains were
pediococcus, including P. acidilactici (1) and P. pentosaceus (3). The strains with good acid-producing capability were X24,
X38, X29, X25, X21, X22, X30 and X35. Strain T7 revealed positive result for all tests of citrate utilization, proteinase
and exopolysaccharide-producing capability. The above findings imply the species diversity of lactic acid bacteria and the
potential presence of high-performance strains in Chinese yak milk cheeses.

Key words: yak milk cheese, lactic acid bacteria, species identification, 16S rRNA sequence analysis, characterization