Pre-Treatment of Industrial Tubing with Aqueous Hop Derived Metabolites Reduces Lactobacillus brevis Biofouling

Abstract Microbial biofilms can establish in numerous areas within the brewery and exposure to these communities of organisms can result in undesirable flavors. Beer transfer lines represent a particular risk for contamination as the lines provide an effective point of nucleation for biofilm colonization if they have been subject to degradation and are not well maintained. Despite the presence of surface imperfections associated with prolonged use, transfer tubing in place for several months within a canning operation was observed to be significantly less capable of hosting microbial growth than comparable tubing that had not been exposed to the product, suggesting that the industrial practice itself had imparted an antibiofilm character to the tubing not originally present in new lines. Using an in vitro assay designed to reconstitute microbial biofouling in this tubing, transfer lines artificially conditioned with beer served to effectively reduce biofouling by the hop acid resistant microorganism Lactobacillus brevis compared to untreated controls. The observed reduction in microbial growth was more pronounced in lines that had been conditioned with highly-hopped beer than moderately-hopped beer. Tubing conditioned with aqueous solutions of hop extracts or hop-associated terpenoid compounds also exhibited a relative resistance to microbial growth. Pre-treatment of tubing with solutions containing major (terpene hydrocarbons) and minor (oxygenated terpenes) hop- associated terpenes reduced L. brevis biofouling relative to untreated controls. Results indicate that conditioning of beer tubing with simple solutions of these compounds may provide a means of protecting against biofouling.