The Metabolism Of The Beer-spoilage Lactic Acid Bacteria And Its Impact On The Quality Of Beer Under Different Environmental Conditions

Beer-spoilage strains are a small number of anaerobic or facultative microorganisms that is harmful to beer quality flavor and microbiological stability of beer. The lactic acid bacteria represent the majority of beer-spoilage bacteria. Hop compounds added to confer bitter flavor on beer are reported to exert an antibacterial effect, which prevents most strains from growing in beer. Beer-spoilage lactic acid bacteria can resist hop compound’s antibacterial effect, with strong ATP-yielding ability in beer.1.A total of 7 strains of beer bacteria were isolated from draft beer. For these 7 bacteria, the homology of 16 S r RNA was analyzed and the phylogenetic tree was structured. These 7 beer bacteria were Lactobacillus genus, including Lactobacillus plantarum, Lactobacillus parabuchneri and Lactobacillus brevis. Variation of beer bacteria membrane lipid composition was consistent with the result of 16 S r RNA. The straight chain unsaturated fatty acids and C18 fatty acids of BN03 were increased with increase of beer content.2.This paper studied the relations between the metabolisms of ATP on beer and hop-resistance ability. By measuring H+-ATPase activities of ten beer-spoilage strains,the impacts of culture time, temperature, substrate content and p H were determined, as well as the lowest line of cell concentration. The spoilage ability of ten beer-spoilage strains was defined. Through beer inoculated beer-spoilage bacteria shows the spoilage ability of beer-spoilage strains by using culture with gradually increasing doses o f hop compounds, the hop-resistance ability of the beer-spoilage lactic acid bacteria was displayed.The results showed that the optimal conditions of H+-ATPase in the cell membrane were as follows: culture time 30 min, temperature 45 ℃,the ATP content 100μ L(1mg/m L),p H5.0. The lowest line of cell concentration is diluting 105 times(The initial OD600 nm is 0.70). The bacteria BN03 shows high ATP-yielding ability. There are close links between the ATP metabolism of bacteria and hop-resistance ability in the 7strains.3.In this study, 7 kinds of beer-spoilage bacteria were inoculated in beer for 18 days, detect the beer sample indicators, including: ATP, ADP, NADH, organic acids,total acids and other indicators, The results showed that different LAB had a significant impact on the quality of beer, and the paper analysed the typical products and the metabolites generated in the fermentation process.