青海黄南州传统发酵牦牛乳制品中乳酸菌的微生物多样性和技术特性

Abstract

Traditional fermented yak milk products in Qinghai, China sustain abundant beneficial microorganisms during long-term production and inheritance. This study investigated the microbial diversity, isolation, identification, and physicochemical characteristics of lactic acid bacteria (LAB) present in traditional fermented yak milk products from Huangnan Prefecture, Qinghai Province. A total of 520 OTUs were obtained via high-throughput sequencing. Alpha and beta diversity analyses confirmed significant differences in bacterial community structure across the 12 samples from different sources. At the phylum level, Firmicutes, Proteobacteria, Bacteroidota and Actinobacteriota were dominant, among which Firmicutes occupied the absolute predominance. The predominant genera were Lactobacillus , Lactococcus , Streptococcus and Acetobacter . All 12 samples contained 11 core OTUs, while obvious heterogeneity existed between individual samples; TQL and DNK4 possessed the largest number of unique OTUs. Additionally, the dominant genera varied greatly among samples: some were dominated by Lactobacillus , while others were predominated by Lactococcus . Using culture-dependent methods, 116 presumptive LAB strains were isolated from the 12 samples, and 31 genetically stable strains were finally screened and identified. Ten strains with a fermentation times shorter than 24 h were selected to evaluate five key fermentation properties, including fermentation time, titratable acidity, viscosity, water-holding capacity and postacidification. Strain TSN-6 ( Lactobacillus helveticus ), DSN-10 ( Lactobacillus delbrueckii subsp. bulgaricus ), DNK1-11 ( Streptococcus thermophilus ) and DNK3-9 ( Lactococcus lactis ) exhibited excellent performance in titratable acidity, viscosity and water-holding capacity, and have great potential to be developed as starter cultures.