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. 2022 Sep 14:13:940611.
doi: 10.3389/fmicb.2022.940611. eCollection 2022.

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

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

Lu Meng et al. Front Microbiol. .

Abstract

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 hblACD and nheABC operons, respectively. In addition, the detection rate of emetic cesB 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 bovine milk and revealed that B. cereus sl contamination should also be monitored in raw milk for ultra-high temperature (UHT) products. This knowledge illustrates that strict cleaning management should be implemented to control B. cereus sl and assure high-quality milk products.

Keywords: B. cereus sl; MLST; dairy farm; proteolytic activity; toxin genes.

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Conflict of interest statement

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Figures

Figure 1
Figure 1
Phylogenetic tree of the 47 B. cereus sl isolates studied and reference strains. Numbers in parentheses indicate how many study isolates are associated with the sequence type (ST).
Figure 2
Figure 2
Proteolytic activity of 42 B. cereus sl strains at 7°C, 25°C, and 37°C. Data represent the mean of proteolytic activity ± SEM (****p < 0.0001).
Figure 3
Figure 3
Percentage of residual proteolytic activity of the protease produced by 42 B. cereus sl isolates at 7°C, 25°C, and 37°C after treat at different temperatures and time. Data represent the mean of residual proteolytic activity percentage ± SEM. Significance compared with each other was represented as a–h (p < 0.01).

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References

    1. Alonso V.P. P., De Oliveira Morais J., Kabuki D. Y. (2021). Incidence of Bacillus cereus, Bacillus sporothermodurans and Geobacillus stearothermophilus in ultra-high temperature milk and biofilm formation capacity of isolates. Int. J. Food Microbiol. 354, 109318. 10.1016/j.ijfoodmicro.2021.109318 - DOI - PubMed
    1. Benahmed M., Leguerinel I., Moussa-Boudjemaa B. (2020). Biodiversity, spoilage capacity and heat resistance ofmesophilic aerobic spores isolated from milk powdersmarketed in Algeria. Int. J. Dairy Technol. 73, 771–780. 10.1111/1471-0307.12715 - DOI
    1. Brillard J., Dupont C. M., Berge O., Dargaignaratz C., Oriol-Gagnier S., Doussan C., et al. . (2015). The water cycle, a potential source of the bacterial pathogen Bacillus cereus. Biomed. Res. Int. 2015, 356928. 10.1155/2015/356928 - DOI - PMC - PubMed
    1. Candelon B., Guilloux K., Ehrlich S. D., Sorokin A. (2004). Two distinct types of rRNA operons in the Bacillus cereus group. Microbiology (Reading) 150, 601–611. 10.1099/mic.0.26870-0 - DOI - PubMed
    1. Chang Y., Xie Q., Yang J., Ma L., Feng H. (2021). The prevalence and characterization of Bacillus cereus isolated from raw and pasteurized buffalo milk in southwestern China. J. Dairy Sci. 104, 3980–3989. 10.3168/jds.2020-19432 - DOI - PubMed

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