In order to enrich the resource of lactic acid bacteria and to systematically clarify the diversity of lactic acid bacteria in traditional Paraguayan fermented dairy products, lactic acid bacterial strains were isolated, purified and identified from traditional Paraguayan fermented milk by combined use of the traditional pure culture method, 16S rRNA gene sequencing and phylogenetic analysis. A total of 79 strains were isolated from eight samples, which were identified to belong to seven species of four genera. Lactococcus lactis was found to be the dominant strain, accounting for 68.35% of the total isolates.

The aim of this paper is to explore the amino acid composition and nutritional evaluation of mare milk and traditional fermented mare milk in two pasture areas of western China. In this study, 40 samples of mare milk and traditional fermented mare milk were collected in the main pastoral areas of Xinjiang and Inner Mongolia. An amino acid automatic analyzer and high performance liquid chromatography were used to determine the composition and content of free amino acids and hydrolyzed amino acids in the samples. The obtained data were analyzed using analysis of variance (ANOVA) and nutritional evaluation was performed. The results showed that there was no significant difference in the total amino acid of mare milk in both areas (P > 0.05); the free amino acid contents of two fermented mare milk samples were generally significantly increased relative to their unfermented counterparts (P < 0.05), and new amino acids with special physiological activities were produced such as gamma-aminobutyric acid (GABA), beta-aminoisobutyric acid (BAIBA) and gammahydroxylysine; the content of sweet amino acid Xinjiang mare milk was significantly increased after fermentation, and the total amino acid content was higher than in fresh mare milk, indicating that fermentation helped improve the flavor of mare milk; the essential amino acid index values of fresh and fermented mare milk from the two areas were all greater than 95, indicating that both fresh and fermented mare milk were high-quality protein sources. Moreover, the nutritional evaluation of fermented mare milk was higher than fresh mare milk in each area.

Another bacterium, identified as Staphylococcus warneri by matrix-assisted laser desorption ionization-time of flight-mass spectrometry (MALDI-TOF-MS), was obtained during the isolation of Staphylococcus aureus from yak milk by using Baird-Parker (BP) medium. The biochemical properties and antibiotic susceptibility of the Staphylococcus warneri strain were examined, and antibacterial experiments were carried out. Also, this study determined antibiotic residues in yak milk. The results showed that the biochemical properties of the obtained strain were consistent with those of Staphylococcus warneri. The strain was highly susceptible to most antibiotics except neomorphine, which had no inhibitory effect on it. Besides, all the yak milk samples were found to be negative for antibiotic residues. Although the opportunistic pathogen Staphylococcus warneri was detected in yak milk, it was sensitive to most antibiotics due to the pure environment of the milk source.