Abstract
Biofilms on the surfaces of milk-processing equipment are often a major source of contamination of dairy products. Members of the genus Bacillus appear to be among the most commonly found bacteria in dairy farms and processing plants. Bacillus species may thrive in dairy farm equipment and in dairy products since they can form robust biofilms during growth within milk. We found that fortification of milk with magnesium mitigated biofilm formation by Bacillus species, and thus could notably reduce dairy product spoilage. We also show that the mode of action of Mg2+ ions is specific to inhibition of transcription of genes involved in biofilm formation. Our further findings indicate that in the presence of Mg2+ bacterial cells are hypersensitive to the heat pasteurization applied during milk processing. Additionally, we demonstrated that enrichment of milk with magnesium improved technological properties of milk products such as soft cheeses. Finally, we report that there is a notable increase in the intestinal bioavailability potential of magnesium from supplemented milk compared with that from non-supplemented milk.
Highlights
Bacterial contamination can adversely affect the quality, functionality, and safety of milk and its derivatives. It appears that the major source of the contamination of dairy products is often associated with biofilms on the surfaces of milk processing equipment.[1]
We recently reported that magnesium ions (Mg2+) affected biofilm formation via down-regulation of the expression of extracellular matrix genes,[18] which suggests that the molecular mechanism behind the inhibitory effect of Mg2+ ions is primarily related to expression of matrix genes
We investigated the potent inhibitory activity of Mg2+ ions on biofilm formation by Bacillus species within milk, and found that bacteria became more sensitive to processing procedures of dairy food, e.g., heattreatment pasteurization, in the presence of Mg2+ ions
Summary
Bacterial contamination can adversely affect the quality, functionality, and safety of milk and its derivatives. Bacterial spores can survive treatment with reagents commonly used in a cleaning-in-place procedures, which include regular cleaning of processing equipment, usually with alkaline and acidic liquids at high temperatures.[13,14] In addition, according to our recent study, Bacillus species form biofilm-related structures termed bundles during their growth in milk.[4] This biofilmassociated phenomenon, which appears to be highly conserved in Bacillus species,[4] may have tremendous undesirable implications in the dairy industry Some of these bacteria produce enzymes—proteases and lipases—that cause off-flavors and curdling in the final product.[10,15]. Milk products, e.g., by promoting clotting in milk and enhancing protein contents in cheeses
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