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Control the growth of biofilms.

As you know, biofilms formed on the surfaces of food processing equipment pose a safety threat because they are difficult to remove or inactivate. They can contaminate foods even if the processing equipment is routinely cleaned. Microbial biofilms found on surfaces create billions of dollars yearly in equipment damage, product contamination, energy losses and medical infections. Conventional approaches used to kill bacteria, such as antibiotics and disinfection, are often ineffective when applied to biofilm bacteria.

For example, contamination of food by L. monocytogenes is thought to occur most frequently in food processing environments where cells persist due to their ability to attach to stainless steel and other materials. Once attached, these cells produce multi-cellular biofilms that resist disinfection and from which cells can detach and contaminate products. The large doses of antimicrobials required to rid systems of biofilms are undesirable environmentally, and perhaps not allowed by some environmental regulations. So new strategies based on a better understanding of how bacteria attach, grow and detach are urgently needed.

The bacteria that attach to a biofilm are able to resist sanitizers and other antimicrobial agents, unlike planktonic or free-living bacteria. So it's important to properly detect and control these films. One way to do this is to use bioreactors and fomenters in which the flow rate of nutrients can be kept constant for a specific period of time.

There are several ways to measure and study bacteria in biofilms, using microscopic beads or scraping, swabbing or rinsing processes. You can monitor the formation of biofilms using microscopy, spectroscopy or nuclear magnetic resonance systems. In addition, biosensors enable you to monitor the films on-line. A biosensor may help in quantifying the development of bacterial biofilms, which in turn helps quantify risk assessment and extend operating cycle times of equipment.

In the food processing environment, biofilms are sources of pre- or post-processing contamination. Cleaning them with detergents, scrubbing food contact surfaces and applying sanitizers are effective ways to control biofilms. Moreover, when designing food processing equipment, the appropriate type of materials should be carefully selected to prevent microbial adhesion to the surface of equipment.

Further information. Sadhana Ravishankar, National Center for Food Safety and Technology, 6502 S. Archer Rd., Summit-Argo, IL 60501; phone: 708-563-8186; fax: 708-563-1873; email:; URL:
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Publication:Microbial Update International
Date:Aug 1, 2004
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