Dairy products are a sector heavily impacted by food loss, often due to bacterial contaminations. A major source of contamination is associated with the formation of biofilms by bacterial species adopted to proliferate in milk production environment and onto the surfaces of milk processing equipment. Bacterial cells within the biofilm are characterized by increased resistance to unfavorable environmental conditions and antimicrobial agents. Members of the Bacillus genus are the most commonly found spoilage microorganisms in the dairy environment. It appears that physiological behavior of these species is somehow depended on the availability of bivalent cations in the environment. One of the important cations that may affect the bacterial physiology as well as survivability are Zn²⁺ ions. Thus, the aim of this study was to examine the antimicrobial effect of Zn²⁺ ions, intending to elucidate the potential of a zinc-based antibacterial treatment suitable for the dairy industry. The antimicrobial effect of different doses of ZnCl₂ was assessed microscopically. In addition, expression of biofilm related genes was evaluated using RT-PCR. Analysis of survival rates following heat treatment was conducted in order to exemplify a possible applicative use of Zn²⁺ ions. Addition of zinc efficiently inhibited biofilm formation by B. subtilis and further disrupted the biofilm bundles. Expression of matrix related genes was found to be notably downregulated. Microscopic evaluation showed that cell elongation was withheld when cells were grown in the presence of zinc. Finally, B. cereus and B. subtilis cells were more susceptible to heat treatment after being exposed to Zn²⁺ ions. It is believed that an anti-biofilm activity, expressed in downregulation of genes involved in construction of the extracellular matrix, would account for the higher sensitivity of bacteria during heat pasteurization. Consequently, we suggest that Zn²⁺ ions can be of used as an effective antimicrobial treatment in various applications in the dairy industry, targeting both biofilms and vegetative bacterial cells.

中文翻译：

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通过诱导锌离子抗生物膜活性减轻与牛奶有关的细菌。

乳制品是受食品损失严重影响的行业，通常是细菌污染造成的。污染的主要来源与在奶类生产环境中以及在奶类加工设备表面上繁殖的细菌所形成的生物膜有关。生物膜内的细菌细胞的特征在于对不利的环境条件和抗菌剂的抵抗力增强。芽孢杆菌属的成员是乳品环境中最常见的腐败微生物。看来这些物种的生理行为某种程度上取决于环境中二价阳离子的可用性。可能会影响细菌生理和生存能力的重要阳离子之一是Zn ²⁺离子。因此，本研究的目的是研究Zn ²⁺离子的抗菌作用，以阐明适用于乳制品行业的锌基抗菌处理的潜力。用显微镜评估了不同剂量的ZnCl ₂的抗菌作用。另外，使用RT-PCR评估生物膜相关基因的表达。为了说明Zn ²⁺离子可能的应用用途，进行了热处理后的存活率分析。锌的添加有效抑制了枯草芽孢杆菌的生物膜形成并进一步破坏了生物膜束。发现基质相关基因的表达明显下调。显微镜评估显示，当细胞在锌的存在下生长时，细胞伸长被抑制。最后，蜡状芽孢杆菌和枯草芽孢杆菌细胞在暴露于Zn ²⁺离子后更容易受到热处理。据信，通过下调参与细胞外基质构建的基因表达的抗生物膜活性将说明热巴氏灭菌过程中细菌的更高敏感性。因此，我们建议Z​​n ²⁺ 离子可在乳品行业的各种应用中用作有效的抗微生物治疗剂，同时针对生物膜和营养细菌细胞。