Microbial attachment and biofilm formation in brewery bottling plants

Microbial attachment and biofilm formation in brewery bottling plants was studied by mounting sterile, stainless steel coupons onto critical sites of the fillers in three breweries. Microbiological samples were taken from the coupons to reveal the primary colonizers in biofilm formation. The bacteria were identified using ribotyping, carbohydrate fermentation tests, and partial 16S rDNA sequencing. The effect of sugars and sweeteners on the attachment of primary colonizers to stainless steel was analyzed with epifluorescence microscopy. The biofilm formation rate was studied for eight weeks by successively dislodging the test coupons from each sampling site and examining them with epifluorescence microscopy. The results showed that primary colonizers accumulated on new stainless steel surfaces within hours after the start of production. Regular daily cleaning reduced the number of microorganisms on the surfaces only momentarily. Canning machines were markedly less prone to accumulation of microorganisms than bottling machines. Gram-negative bacteria, yeasts, and molds were the first to colonize the surfaces. Attachment of primary colonizers to stainless steel was increased by sugars and sweeteners. Horizontal surfaces were prone to microbial accumulation and should be avoided in constructions as much as possible. Furthermore, biofilm formation occurred on certain surfaces despite daily cleaning and disinfection.