Acyl Homoserine Lactone Production of Brewery Process Surface Bacteria

The aim of this study was to find out whether the first bacterial colonizers of brewery process surfaces after washing produce acyl homoserine lactone (AHL) quorum sensing signalling molecules. Microbial attachment and biofilm formation was studied by mounting sterile uncoated and coated stainless steel coupons onto critical places of the filling machines in three breweries. In the present study 26 previously deposited bacterial strains, as well as approximately 2,300 colonies from 76 process surface samples, were screened using reporter bacteria Chromobacterium violaceum CV026 and Agrobacterium tumefaciens NTLR4. AHL-producing bacteria were detected both from process samples and among the previous isolates. From the process samples, up to 15% of the screened colonies produced AHL molecules. Production of long chain AHLs was more common than short chain AHLs. The identified AHL-producing isolates belonged to the genera Pseudomonas, Serratia, Hafnia, Rahnella, Enterobacter and Aeromonas, which all belong to commonly found primary colonizers of brewery process surfaces. The same microbial genera producing AHL molecules were found from different breweries. Brewery filling equipment is susceptible to microbial attachment and accumulation on surfaces. In the future, inhibition of quorum sensing could be one additional way of controlling biofilm formation.