Biofilms in food factories, especially ones formed by bacteria that cause human disease, are a major concern and the food industry invests heavily in understanding where and how biofilms form, to keep our food safe.
The sticky, glue like part of a biofilm, called the extracellular matrix, is mainly composed of polysaccharides like cellulose, proteins and exogenous DNA. This matrix can be fixed to hard surfaces (e.g. factory equipment, transport, dispensing and storage surfaces) or to the food being processed (vegetables, meat, bones, fruits). The extracellular matrix is responsible for persistence of these biofilms in food factories. Biofilms generate complex gradients of nutrients and oxygen, contain extracellular digestive enzymes, facilitate transfer of cell communication molecules, and protect the embedded cells against toxic compounds.
Biofilm formation confers many advantages to the microbes present in a food factory environment, such as physical resistance (against desiccation), mechanical resistance (against liquid streams in pipelines) and chemical protection (against chemicals, antimicrobials and disinfectants used in the industry).
Biofilms can form quickly in food factories. Biofilm establishment begins with conditioning of the surfaces and the reversible binding of cells to that surface, followed by irreversible binding and the development of micro colonies, ultimately forming a multi-layered structure giving rise to a complex ecosystem ready for dispersion. See the section on biofilm structure for more detail.
Some biofilm-forming species in food factories can be human pathogens and controlling these is critical to the food industry. These pathogens are able to develop biofilm structures on artificial substrates that are common in the food industry: stainless steel, polyethylene, wood, glass, polypropylene, rubber.
Biofilms can also corrode metal surfaces and alter the properties of food they come in contact with (because they produce enzymes that degrade food) all of which is important in the industry. As an example, in dairy factories numerous processes and structures (raw milk tanks, pipelines, butter centrifuges, cheese tanks, pasteurizers and packing tools) provide surfaces for biofilm formation; and these biofilms have the potential to include various damaging species including psychrotrophic Pseudomonas spp. and the thermophilic species Geobacillus stearothermophilus. Fresh fish products may also suffer from biofilm formation by pathogenic species (Aeromonas hydrophila, L. monocytogenes, S. enterica or Vibrio spp.), with significant health and economic implications.
Furthermore, genetic variation in biofilm-forming bacterial species can give rise to completely different types of biofilm depending on the environmental conditions. This complexity, alongside the high diversity of affected environments and the variety in colonising bacterial species, complicates biofilm eradication in the food industry. Mixed biofilms also show higher resistance to disinfectants such as biocides.
Further reading on biofilms in food factories
Biofilms in the Food Industry: Health Aspects and Control Methods. Galié Serena, García-Gutiérrez Coral, Miguélez Elisa M., Villar Claudio J., Lombó Felipe. Frontiers in Microbiology, Vol 9, 2018, pp898. https://doi.org/10.3389/fmicb.2018.00898
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Food-borne diseases associated with bacterial biofilms on food ingredients or factory equipment happen as a result of direct infection (food poisoning) or by intoxication from the compounds that microbes produce (their biproducts). For example, toxins secreted by biofilms within food processing plants can contaminate food products, causing individual or multiple intoxications. In either case, the […]