Abstract
Milk microbiota has a great influence on the safety and quality of dairy products. However, few studies have investigated the variations of bacterial composition in raw milk. In this study, raw milk samples were collected in 12 successive months, and their bacterial compositions were determined by 16 S rRNA gene sequencing. The highest diversity of bacterial composition was detected in June, while the lowest was in December. Firmicutes, Proteobacteria and Actinobacteria were the most abundant phyla and exhibited a counter-balanced relationship. Pseudomonas, Lactococcus and Acinetobacter were the most prevalent genera (>1%), and a tiny core microbiota (Acinetobacter and Pseudomonas) was observed. Temperature and humidity were the determining factors for most variation in bacterial compositions at both the phylum and genus levels. Higher abundances of Pseudomonas, Propionibacterium and Flavobacterium were correlated with low temperature. Furthermore, Pseudomonas/Propionibacterium and Lactobacillus/Bifidobacterium were two pairs of genera that had synergistic effects. Associations between the microbiota and milk quality parameters were analyzed. The abundances of Propionibacterium and Pseudoalteromonas were negatively correlated to total bacterial count, which meant that they helped to maintain milk quality, while a series of environmental microorganisms contributed to the spoilage of raw milk.
Highlights
Bacterial contamination of dairy products is a major concern throughout the world[4], as dairy production and consumption have expanded extensively during the last decade
To get a better understanding of indigenous bacterial compositions and to guarantee the safety and quality of raw milk and dairy products, we investigated the bacterial communities of raw milk from ten dairy farms in Shanghai (China) with high-throughput sequencing technology
The operational taxonomic unit (OTU), or group of 16 S rRNA genes, was set at 97% similarity to estimate the diversity of the bacterial community
Summary
Bacterial contamination of dairy products is a major concern throughout the world[4], as dairy production and consumption have expanded extensively during the last decade. The indigenous microflora in raw milk has a direct impact on the subsequent development of dairy products[7]. Descriptions of microbial composition and distribution would provide necessary information for the risk assessment and quality control of raw milk throughout the year. It ensures the high performance and traceability of the subsequent pasteurization and processing. To get a better understanding of indigenous bacterial compositions and to guarantee the safety and quality of raw milk and dairy products, we investigated the bacterial communities of raw milk from ten dairy farms in Shanghai (China) with high-throughput sequencing technology. The effects of temperature and humidity were considered in a correlation analysis with the bacterial communities
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