Hutchings Carmel, Rajasekharan Satish Kumar, Reifen Ram, Shemesh Moshe
Department of Food Science, Institute for Postharvest Technology and Food Sciences, Agricultural Research Organization (ARO), Volcani Center, Rishon LeZion 7505101, Israel.
The Robert H. Smith Faculty of Agriculture, Food and Environment, Institute of Biochemistry, Food Science and Nutrition, The Hebrew University of Jerusalem, Rehovot 7610001, Israel.
Foods. 2020 Aug 11;9(8):1094. doi: 10.3390/foods9081094.
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 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 Zn ions. Thus, the aim of this study was to examine the antimicrobial effect of Zn ions, intending to elucidate the potential of a zinc-based antibacterial treatment suitable for the dairy industry. The antimicrobial effect of different doses of ZnCl 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 Zn ions. Addition of zinc efficiently inhibited biofilm formation by 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, and cells were more susceptible to heat treatment after being exposed to Zn 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 Zn ions can be of used as an effective antimicrobial treatment in various applications in the dairy industry, targeting both biofilms and vegetative bacterial cells.
乳制品是一个受食物损失严重影响的行业，这通常是由于细菌污染所致。一个主要的污染源与细菌在牛奶生产环境以及牛奶加工设备表面形成生物膜有关，这些细菌适应在这样的环境中增殖。生物膜内的细菌细胞具有对不利环境条件和抗菌剂抵抗力增强的特点。该属的成员是乳制品环境中最常见的腐败微生物。这些物种的生理行为似乎在某种程度上取决于环境中两价阳离子的可用性。锌离子是可能影响细菌生理以及生存能力的重要阳离子之一。因此，本研究的目的是检验锌离子的抗菌效果，旨在阐明适合乳制品行业的锌基抗菌处理的潜力。通过显微镜评估不同剂量氯化锌的抗菌效果。此外，使用逆转录聚合酶链反应（RT-PCR）评估生物膜相关基因的表达。进行热处理后存活率的分析，以举例说明锌离子可能的实际应用。添加锌有效地抑制了生物膜的形成，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。显微镜评估表明，当细胞在锌存在的情况下生长时，细胞伸长受到抑制。最后，在暴露于锌离子后，[具体细菌名称1]和[具体细菌名称2]细胞对热处理更敏感。据信，在参与细胞外基质构建的基因下调中表现出的抗生物膜活性，将解释细菌在热巴氏杀菌过程中更高的敏感性。因此，我们建议锌离子可作为一种有效的抗菌处理方法，用于乳制品行业的各种应用，针对生物膜和营养细菌细胞。
