Brewery-related Enterobacteriaceae

However, several incidents of the occurrence of enteric pathogens in low alcohol and alcohol-free beers and traditional beer-like products have been reported (Menz et al., 2010, 2009 Pattison, Geomaras, von Holy, 1998 Shayo, Kamala, Gidamis, 

Obesumbacterium proteus biogroup-1 are supposed to be more closely related to Hafnia alvei, a common pathogen, and are postulated to be the metabolicaUy inactive strain that is adapted to brewery enviromnents (Priest et al., 1973 Farmer, 1984). The strains from biogroup-2 are more common dwellers of brewery enviromnents and have not been reported from any other source (Priest Barker, 2010). Priest and Barker (2010), assigned 0. proteus biogroup-2 to a newly proposed genus Shimwellia and the species as Shimwellia pseudoproteus. 

Nitrosation of amines with suitable A/-nitrosation agent 

Mixed and uncontrolled fermentation beers such as lambic beers (Belgium) and coolship ales (United States) are produced by fermentation of wort by a mixture of brewery resident yeast and bacteria (Bokulich Bamforth, 2013). During the early stages of fermentation. Enterobacteria such as Klebsiella, Enterobacter, Citrobacter, Serratia and Pectobacter are predominant and contribute to the aroma of lambic beers by producing organic acids, 2, 3-butanediol, ethyl acetate and some higher alcohols (BokuUch et al., 2012). 

A PCR-based method for specific detection and discrimination of O. proteus biogroup-2 strains from O. proteus biogroup-1 and other related microorganisms has been documented (Maugueret Walker, 2002). Characterisation of O. proteus biogroup-1 strains using automated ribotyping and PCR-based methods have also been reported (Koivula, Juvonen, Haikara, Suihko, 2006). 

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AAB are still a common contaminant in beer dispense. Brewery-related Enterobacteriaceae need to be monitored in breweries due to the high level of hygiene required and also due to their role in production of ATNC in beer. Selective Enterobacteriaceae also play a significant role in flavour development in lambic and American cool-ship ales. Zymomonas seems to be limited to primed beer in the brewing industry, but strains of Zymomonas are still a problem in the cider industry. 

Certain species of Enterobacteriaceae, especially 0. proteus, could utilise nitrates as electron acceptors for anaerobic respiration, resulting in reduction of nitrate into nitrite. Nitrite further could possibly react with secondary amines present in the wort, forming (V-nitrosoamine (Figure 8.2). A -nitrosomines are carcinogenic in nature (Smith, 1994). Hence, a considerable amount of apparent total N-nitroso compounds (ATNCs) represents a possible risk to health, and consequently their concentration is strictly monitored and limited to 20 gg/1 (Maiguerite and Walker, 2002). Because of the risk of W-nitroso compounds, the Enterobacteriaceae species related to brewery environments are monitored. 

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