Biofilm in food processing Petra Sedláčková

Biofilm – biologically active matrix of cells and extracellular substances in association with a solid surface. Food-borne pathogens and spoilage microorganisms accumulate as biofilm on stainless steel, aluminium, glass, Buna-N, teflon steel and nylon materials typically found in food-processing. Biofilm causes serious problem – cross contamination and post-processing contamination.

Mechanism of biofilm formation Conditioning of a surface – the accumulation of macromolecules at the solid-liquid interface on food- contact surface. Adhesion of cells – attachment of microorganisms to the conditioned surface. Formation of microcolony – layer of cells covering the surface. Biofilm formation – continuous attachment of the bacterial cells with associated EPS production.

Reversible adherence. Planktonic cells (a) in the bulk fluid come in contact with the solid surface (b). The cells then desorb from the surface and become planktonic cells again (c). Solid surface Bulk fluid (a) (b) (c)

Irreversible adherence. Planktonic cells (a) in the bulk fluid come in contact with the solid surface. If the forces that hold the cell on the surface are strong enough, the cell is not easily removed and may produce exopolymers that help anchor the cell to the surface (b). Solid surface (a) (b) polysaccharide Bulk fluid

Quantification of attachment  Direct methods removal of the cells and counting by traditional plating methods direct counting of the cells using microscopic techniques  Indirect methods measuring cellular components that have accumulated on the surface - protein, ATP or exopolysaccharides.

Control and removal of biofilm Physical methods – super-high magnetic fields, high pulsed electrical fields, low electrical fields in combination with organic acid Chemical methods – application of a disinfectant, sanitizers (hypochlorites, iodophores, quarternary ammonium compounds) for successful biofilm control with mechanical treatment Biological methods – bacteriocins, enzymes

Biofilm may be the problem of following areas: dental caries colonization of medical implants fouling of drinking water systems food processing environments Biofilm is positive for: treatment of waste streams the production of food grade ingredients such as acetic acid