生物膜的形成与控制

生物膜对食品工厂的危害极大,可使微生物残存增加,加工车间设备无法适当清洗、清毒、产品受到污染,甚至危害产品的安全、食品加工厂欲控制生物膜的形成,应从设计、生产环节着手,设计出良好的生产环境,注意清洗频率,使用正确的清洗、消毒方法,严格控制生物膜的形成,才难保障产品的卫生安全。     

肉类食品生物膜的形成机制及预防措施

在肉及肉制品加工及贮藏过程中，如处理不当就会引起细菌污染，并形成细菌生物膜而造成肉制品腐败、致病。生物膜是具有三维结构的微生物群落，是微生物抵抗外界不良环境的一种特殊生长方式，它可以改善恶劣环境及抑菌剂对微生物的影响。腐败菌和致病菌均可形成生物膜，其对肉制品加工业的危害极大。本文主要概述近5年来国内外关于肉类食品细菌生物膜形成的机制、影响及其预防和控制措施，旨在为肉类食品加工中各种细菌生物膜形成及控制提供理论和应用参考。     

群体感应在食源性微生物生物膜形成中的作用

生物膜(Biofilm)是由众多微生物聚集黏附在物体表面形成的多细胞群体结构,多种食源性微生物均能形成相应的生物膜,且该现象的产生对食品加工与安全有着重要影响。群体感应(Quorum sensing,QS)已被证明是调控生物膜形成的重要因素。文章主要介绍了群体感应对几种食源性细菌及真菌生物膜形成的调控作用,旨在为食品加工过程中微生物生物膜的控制与利用提供参考。     

调控生物膜形成机制的研究进展

微生物在生长过程中聚集在一起会形成生物膜。生物膜的形成给医疗、食品、环境等行业带来了很大的问题,因此微生物生物膜的形成机制也成了当今研究的热点。以枯草芽孢杆菌为例描述生物膜的分类、组成和生物膜形成的调控途径,其中重点介绍Spo0A调节机制、SinR-SlrR调节机制、abh调节机制,并且对生物膜的研究前景进行展望。     

食品加工环境胁迫因素对单核细胞增生李斯特菌生物膜形成的影响研究进展

单核细胞增生李斯特菌（以下简称单增李斯特菌）生物膜的生长可导致反复的食物污染。食品加工储藏常用的冷藏、干燥、酸处理以及消毒剂处理等使微生物长期处于胁迫环境下，对生物膜的形成产生影响。本文总结了常见的食品加工胁迫因素对单增李斯特菌生物膜形成的影响，其中重点介绍消毒剂处理对单增李斯特菌生物膜形成的影响，同时从膜流动性相关的适应策略、生物膜形成相关蛋白和基因调控表达的角度阐述胁迫条件下单增李斯特菌生物膜的形成机制。胁迫环境下单增李斯特菌生物膜形成的研究有助于揭示真实环境下其生物膜的形成及变化规律；充分考虑环境因素设定清洁、消毒标准有利于降低食源性致病菌传播的潜在风险。     

冷等离子体对微生物生物膜抑制作用的研究进展

日益严峻的生物膜污染给食品和医疗等行业的生产安全带来了巨大的威胁。与一般存在于食品中的浮游微生物不同,微生物形成的生物膜有其独特的结构和功能性质,因此生物膜对杀菌处理具有更强的抵抗能力,而寻找绿色环保的抗生物膜技术也成为人们日益关注的问题。作为一种新型的杀菌技术,冷等离子体杀菌操作简单、杀菌效果显著、能耗低,还可以很好地保持食品颜色、质地以及营养价值,在食品领域引起了广泛关注。本综述主要对冷等离子体破坏生物膜形成的机理、影响因素以及应用情况3 个方面进行介绍,旨在为冷等离子体抗生物膜技术在食品工业中的应用提供理论支持。     

单核细胞增生李斯特菌对季铵盐类消毒剂的耐受机制及其防控研究进展

单核细胞增生李斯特菌（以下简称“单增李斯特菌”）是一种常见的食源性病原菌，可通过群体感应在不锈钢食品加工设备表面形成单一或多物种生物膜，成为食品潜在的污染源。季铵盐类消毒剂常用于食品企业加工设备表面的清洗消毒，而单增李斯特菌生物膜在主动外排泵系统、应激反应、基因调控等多种机制的介导下可对其产生耐受性。本文综述了单增李斯特菌生物膜的形成及耐受机制，汇总了近年来物理杀菌以及新型组合杀菌技术在食源性单增李斯特菌防控中的应用，为新型高效杀菌技术的开发提供思路，也为企业建立单增李斯特菌及其他微生物防控措施提供重要参考。     

超声技术抑制微生物生物膜污染：机制、影响因素及其在肉及肉制品中的应用

由微生物生物膜污染所造成的疾病爆发会导致重大公共卫生问题发生。为抑制生物膜污染,食品工业目前广泛应用的方法包括热处理、添加化学杀菌剂等传统方法。但是热处理会导致肉及肉制品等食品的营养物质流失,并破坏产品的质构、风味特性,而化学杀菌剂的添加不符合当前安全健康的消费理念。此外,生物膜特有的结构和功能特性赋予其抵抗环境胁迫的能力,因而对大多数化学杀菌剂具有一定的抗性。因此,寻找安全、高效的抑制生物膜手段是目前食品行业亟待解决的问题。超声技术作为一种非热处理方法用于抑制生物膜污染越来越受到关注。与传统的杀菌技术相比,超声技术不仅具有操作简便、节约能源和延长食品货架期等特点,并且在保持食品感官、功能特性及营养价值方面起到了非常重要的作用。本文综述生物膜形成的机制、代谢过程及影响因素,并且对超声技术进行概述,在此基础上介绍了超声技术抑制微生物生物膜污染机制及影响因素,最后讨论了超声技术在肉及肉制品中的应用和对未来的展望。     

美国肉类食品安全控制体系

美国的肉类安全卫生控制策略，概括起来主要包括动物卫生控制、残留监控、食品源性微生物的监测及在加工厂推行HACCP计划几个方面。     

金黄色葡萄球菌生物膜形成相关基因及检测方法的研究进展

金黄色葡萄球菌在食品加工设备表面和储藏过程中极易形成生物膜,形成的生物膜很难被彻底清除,并且可以保护膜内生长的细菌,从而给食品安全乃至整个食品产业带来了安全隐患。该文综述了生物膜形成过程中相关基因和目前常用生物膜定量定性检测方法的最新研究进展,为深入了解生物膜形成机理以及定量定性检测相关方法提供一定的参考。     

肉类保藏技术(十五) 食品工业中生物被膜的形成及其控制

生物被膜对食品工业的危害极大,可使微生物残存增加,加工设备无法严格清洗、消毒,产品受到污染。本章综述了食品加工过程中生物被膜的形成特点及其控制方法,并对近几年生物被膜的检测方法进行了介绍。     

Promising strategies to control persistent enemies: Some new technologies to combat biofilm in the food industry—A review

Biofilm is an advanced form of protection that allows bacterial cells to withstand adverse environmental conditions. The complex structure of biofilm results from genetic-related mechanisms besides other factors such as bacterial morphology or substratum properties. Inhibition of biofilm formation of harmful bacteria (spoilage and pathogenic bacteria) is a critical task in the food industry because of the enhanced resistance of biofilm bacteria to stress, such as cleaning and disinfection methods traditionally used in food processing plants, and the increased food safety risks threatening consumer health caused by recurrent contamination and rapid deterioration of food by biofilm cells. Therefore, it is urgent to find methods and strategies for effectively combating bacterial biofilm formation and eradicating mature biofilms. Innovative and promising approaches to control bacteria and their biofilms are emerging. These new approaches range from methods based on natural ingredients to the use of nanoparticles. This literature review aims to describe the efficacy of these strategies and provide an overview of recent promising biofilm control technologies in the food processing sector.     

Biofilm Formation and Control in Food Processing Facilities

Microorganisms on wet surfaces have the ability to aggregate, grow into microcolonies, and produce biofilm. Growth of biofilms in food processing environments leads to increased opportunity for microbial contamination of the processed product. These biofilms may contain spoilage and pathogenic microorganisms. Microorganisms within biofilms are protected from sanitizers increasing the likelihood of survival and subsequent contamination of food. This increases the risk of reduced shelf life and disease transmission. Extracellular polymeric substances associated with biofilm that are not removed by cleaning provide attachment sites for microorganisms newly arrived to the cleaned system. Biofilm formation can also cause the impairment of heat transfer and corrosion to metal surfaces. Some of the methods used to control biofilm formation include mechanical and manual cleaning, chemical cleaning and sanitation, and application of hot water.     

Biofilm formation by salmonella spp. on food contact surfaces and their sensitivity to sanitizers

Biofilm formation by two poultry isolates of Salmonella on three commonly used food contact surfaces viz plastic, cement and stainless steel were studied. Biofilm formation of both the isolates showed a similar trend with the highest density being on plastic followed by cement and steel. Salmonella weltevreden formed biofilm with a cell density of 3.4 x 10(7), 1.57 x 10(6) and 3 x 10(5) cfu/cm2 on plastic, cement and steel respectively while Salmonella FCM 40 biofilm on plastic, cement and steel were of the order of 1.2 x 10(7), 4.96 x 10(6) and 2.23 x 10(5) cfu/cm2 respectively. The sensitivity of the biofilm cells grown on these surfaces to different levels of two sanitizers namely hypochlorite and iodophor for varying exposure times was studied. Biofilm cells offered greater resistance when compared to their planktonic counterparts. Such biofilm cells in a food processing unit are not usually removed by the normal cleaning procedure and therefore could be a source of contamination of foods coming in contact with such surfaces.     

Biofilm formation by Escherichia coli in hypertonic sucrose media

High osmotic environments produced by NaCl or sucrose have been used as reliable and traditional methods of food preservation. We tested, Escherichia coli as an indicator of food-contaminating bacterium, to determine if it can form biofilm in a hyperosmotic environment. E. coli K-12 IAM1264 did not form biofilm in LB broth that contained 1 M NaCl. However, the bacterium formed biofilm in LB broth that contained 1 M sucrose, although the planktonic growth was greatly suppressed. The biofilm, formed on solid surfaces, such as titer-plate well walls and glass slides, solely around the air–liquid interface. Both biofilm forming cells and planktonic cells in the hypertonic medium adopted a characteristic, fat and filamentous morphology with no FtsZ rings, which are a prerequisite for septum formation. Biofilm forming cells were found to be alive based on propidium iodide staining. The presence of 1 M sucrose in the food environment is not sufficient to prevent biofilm formation by E. coli.     

Removal of Salmonella enterica serovar Typhimurium and Cronobacter sakazakii biofilms from food contact surfaces through enzymatic catalysis

Bacterial biofilms are highly difficult to control, hence significant economic resources have been allocated to develop strategies to eradicate them. This study evaluated the effect of an enzymatic treatment to be used as a cleaning product to control the presence of biofilms. Two different materials used in the food industry, polystyrene and stainless steel, were tested using Salmonella Typhimuirum and Cronobacter sakazakii. Biofilm formation was carried out by inoculating the surfaces with a standardized concentration of 4 log (CFU cm⁻²) and incubated for 48 hr with renewal of nutrients. The biofilm formation and subsequent enzymatic treatment were quantified using fluorescence microscopy and the conventional culture method. The enzymatic treatment showed significant reductions of 2–3 log (CFU cm⁻²) in biofilm cells, which was attributed to the degradation of the extracellular matrix and the further detachment of both microorganisms. The maximum biofilm detachment obtained with the preventive formula was 46.67%; however, this percentage could be increased by applying an aggressive treatment or by adding a subsequent disinfection step that would eliminate adhered microbial cells. Further, the enzymatic cleaning treatment could be exploited as a potent technology to control bacterial adherence and biofilm formation in the food industry.     

从腐败食品中分离的乳酸菌生物被膜形成的影响因素

从腐败的蔬菜和肉质食品中分离筛选乳酸菌(LAB),并以其作为研究对象,对乳酸菌生物成膜不同影响因素进行研究。生化分离鉴定乳酸菌,在不同的营养物质浓度及培养条件下,用96孔板法检测乳酸菌成膜。在无外添加物,37℃和42℃的培养温度,pH4有利于乳酸菌生物膜的形成,低温不利于生物膜的形成。低浓度的NaCl可促进LAB形成生物膜,但高于某浓度,就抑制LAB成膜。不同LAB菌株对不同葡萄糖浓度成膜效果不同,且与温度交互作用。结果表明,腐败食品中乳酸菌具有一定的生物被膜形成能力,控制乳酸菌生物膜的形成对于防治食品的腐败变质具有一定的意义。     

生物膜状态对食源性致病菌耐药与毒力的影响研究进展

生物膜是细菌抵御不利环境维持群体稳定性的一种常见的群落形态。生物膜状态增强了食源性致病菌的抗逆性和持久存活力,促进了细菌间的信息传导和物质交换。特别是生物膜状态显著增强了菌株对抗生素的耐受能力,提升了可移动元件在细菌间的转移效率,并且生物膜状态下的细菌具备更强的入侵和感染能力,成为食品安全和人类健康的重要危害。基于此,本文将从生物膜的结构特征与异质性、生物膜对基因突变和基因水平转移的影响、以及群体感应调控等多个角度,简述生物膜状态影响食源性致病菌耐药和毒力的研究进展,以期为深入研究生物膜的生物功能与危害防控提供新的思路。     

Assessment of a regulatory sanitization process in Egyptian dairy plants in regard to the adherence of some food-borne pathogens and their biofilms

Food-borne pathogens may develop certain strategies that enable them to defy harsh conditions such as chemical sanitization. Biofilm formation represents a prominent one among those adopted strategies, by which food-borne pathogens protect themselves against external threats. Thus, bacterial biofilm is considered as a major hazard for safe food production. This study was designed to investigate the adherence and the biofilm formation ability of some food-borne pathogens on stainless steel and polypropylene surfaces using chip assay, and to validate regular sanitizing process (sodium hypochlorite 250mg/L) for effective elimination of those pathogens. Sixteen pathogenic bacterial strains, previously isolated from raw milk and dairy products at Zagazig city, Egypt (9 Staphylococcus aureus, 4 Cronobacter sakazakii and 3 Salmonella enterica serovar Typhimurium), were chosen for this study. Strains showed different patterns of adherence and biofilm formation on tested surfaces with minor significance between surfaces. The ability of sodium hypochlorite to completely eradicate either adhered or biofilm-embedded pathogens varied significantly depending on the strain and type of surface used. Whilst, sodium hypochlorite reduced tested pathogens counts per cm(2) of produced biofilms, but it was not able to entirely eliminate neither them nor adherent Cronobacter sakazakii to stainless steel surface. This study revealed that biofilm is considered as a sustainable source of contamination of dairy products with these pathogens, and also emphasized the need of paying more attention to the cleaning and sanitizing processes of food contact surfaces.