Part 1: What are Biofilms?In nature, most bacteria do not exist as suspended (planktonic-free floating) cells. Bacteria live in a group (mass of bacterial cells) attached to each other and to surfaces, in a biofilm form. A biofilm is as a complex community of microorganisms, embedded in self-created extracellular polymeric substances (EPS). Therefore, the biofilm is a microbial population adherent to each other and to surfaces or interfaces enclosed in the matrix. In this complex biofilm network of EPS, the bacterial cells perform less as individual cells and more as a collective living system, frequently creating channels to deliver nutrients and water to the cells located inside the biofilm. Bacteria create biofilm as a protection mechanism, for better survival in the environment. Cells in a biofilm are more resistant to cleaning and disinfection processes in the food industry. The bacteria in the biofilm attaches so firmly to the equipment’s surface that it becomes resistant to conventional sanitation procedures used by the food industry. Various techniques such as molecular methods, chemical methods, and physical methods have been used to better understand the complex mechanism of biofilm formation, and to get an insight into how to create a process that will eliminate the biofilm formation and/or inactivate cells within the biofilm. Moisture and nutrients from food (organic and inorganic material) are commonly found on production lines. These two elements bond together to create a conditioning layer. This layer allows for the initial attachment of the bacterial cells to the surface of the layer and the secretion of EPS. The production of ESP enhances the biofilm attachment to the food contact surfaces and protects the cells within the biofilm from the external stresses such as sanitizing agents.
How is Biofilm Formed?The formation of biofilm can be described as a stepwise process, as shown in Figure 1, consisting of:
- Initial reversible attachment of the planktonic (free-floating) bacteria cell to the surface
- Irreversible attachment by the production of EPS
- Bacteria multiplication and development of biofilm structure
- Development of a microcolony covered by mature biofilm, stabilizing the microcolony from environmental stress
- Dispersion of cells from the biofilm into the surrounding, and the return of cells to their planktonic form.