Characterization and spoilage potential of Bacillus cereus isolated from farm environment and raw milk

作者：Lu Meng, Ruirui Zhang, Lei Dong, Haiyan Hu, Huimin Liu, Nan Zheng, Jiaqi Wang, Jianbo Cheng · 发表于：Frontiers in Microbiology · 年份：2022 · DOI：10.3389/fmicb.2022.940611 · 被引用次数：27 · 研究领域：Bacillus and Francisella bacterial research、Identification and Quantification in Food、Microbial Inactivation Methods

Bacillus cereus sensu lato ( B. cereus sl ) is important spoilage bacteria causing milk structure and flavor changes and is ubiquitous in the environment. This study addresses the biodiversity, toxicity, and proteolytic activity of B. cereus sl from 82 environmental samples and 18 raw bovine milk samples from a dairy farm in the region of Tianjin. In sum, 47 B. cereus sl isolates were characterized through biochemical tests, 16S rRNA gene sequencing, and panC gene analysis. Fourteen sequence types (STs) of B. cereus sl were found in raw bovine milk samples, and five new STs (ST2749, ST2750, ST2751, ST2752, and ST2753) were identified in this study. ST1150 was the dominant ST, associated with fecal, air, drinking water, teat skin, teat cup, and teat dip cup. The results of toxin gene analyses showed that 12.77% and 8.51% of isolates carried hbl ACD and nhe ABC operons, respectively. In addition, the detection rate of emetic ces B gene was 21.28%. B. cereus sl demonstrated high spoilage potentials even at 7°C, which has the proteolytic activity of 14.32 ± 1.96 μmol of glycine equivalents per ml. Proteolytic activities were significantly ( p < 0.05) decreased after the heat treatment. The residual activity of protease produced at 7°C was significantly higher than that produced at 25°C and 37°C after treatment at 121°C for 10 s and 135°C for 5 s ( p < 0.01). Together, the results provide insights into the characteristics of B. cereus sl from farm environment and raw...