Beer-spoilage Strains Research Articles

Monoclonal Antibodies Specific for the Beer-Spoilage Ability of Lactic Acid Bacteria

Lactobacillus brevis, L. lindneri, and Pediococcus damnosus are primary dangerous contaminants for packaged beer; however, all of the strains classified in these species are not able to grow in beer. Our goal was to obtain monoclonal antibodies (MAbs) specific for the beer-spoilage ability of lactic acid bacteria. Mice were immunized with whole cells of lactic acid bacteria cultured in beer, and three MAbs (BLb2F37, BG3A5b4, and PQ3H8a9) were obtained. The BLb2F37 reacted with all beer-spoilage strains of L. brevis and several beer-spoilage strains of P. damnosus, whereas it did not react with the nonbeer-spoilage strains of L. brevis, P. damnosus, and other lactic acid bacteria. The PQ3H8a9 significantly reacted with all the beer-spoilage strains of P. damnosus and also reacted weakly with many of the beer-spoilage strains of L. brevis. The BG3A5b4 specifically reacted with L. lindneri. When the lactic acid bacteria growing in beer were inoculated and successively cultured in modified DeMan-Rogosa-Sharpe broth (pH 5.2), L. brevis began to lose reactivity with the MAbs, whereas L. lindneri and P. damnosus did not. Culturing in medium including isohumulones or treatment of cells with sodium hydroxide improved the reactivity of L. brevis with the MAbs; however, the improved reactivity was not as high as the reactivity of L. brevis growing in beer. It was suggested that the antigens were optimally expressed on the cells growing in beer regardless of the presence of the isohumulones. Using these MAbs, we also developed a simple, rapid, and sensitive kit for prediction of the beer-spoilage ability of lactic acid bacteria.

Classification and identification of strains of Lactobacillus brevis based on electrophoretic characterization of d-lactate dehydrogenase: Relationship between d-lactate dehydrogenase and beer-spoilage ability

The cell-free extracts of 60 strains which were identified phenotypically as being those of Lactobacillus brevis, including 48 isolates from the environment and 12 reference strains, were applied to polyacrylamide gel electrophoresis for extracting their NAD-dependent d- and l-lactate dehydrogenases (LDH). These strains were divided into 5 groups, i.e., Groups A, B, C, D, and E, on the basis of the electrophoretic mobilities of their d-LDH. The strains showed variations in their carbohydrate fermentation patterns. No relationship between the profile of d-LDH and the carbohydrate fermentation pattern was recognized. However, there appeared to be a relationship between the d-LDH profile and the beer-spoilage ability, because 40 out of 44 beer-spoilage strains identified as L. brevis were classified to Group B. We purified d-LDHs from the so-called complete beer-spoilage strain SBC 8002 of LDH Group B and from the non beer-spoilage strains JCM 1059 T of LDH Group A and AHU 1508 of LDH Group C. Although the purified d-LDHs had the same molecular weight (84 kDa), each possessed a different optimum pH, optimum temperature, and isoelectric point. The aforementioned parameter values for the enzyme from the so-called complete beer-spoilage strain SBC 8002 of LDH Group B were 10.0, 50°C, and 4.1, respectively; this strain was discriminated from the d-LDHs of the other two non beer-spoilage strains especially by its optimum temperature (50°C).

Purification and partial characterization of an antigen specific to Lactobacillus brevis strains with beer spoilage activity

Certain Lactobacillus brevis strains are resistant to hop-derived compounds such as isohumulone and are able to grow in beer. In this study, we raised an antiserum against our beer spoilage laboratory strain L. brevis 578 which reacted with 23 of 24 beer spoilers and two of 13 non-spoilers in precipitation reactions using 0.5 M NaOH cell extracts. This specific antigen to the beer spoilage L. brevis strains (SABSL) was demonstrated to be located beneath the S-layer proteins by agglutination reactions using S-layer protein-stripped cells obtained by treatment with 0.1 M NaOH. SABSL was purified using an affinity column coupled with an antibody against SABSL. The purified antigen was hydrolyzed with 2 M HCl and the hydrolyzate was analyzed by thin-layer chromatography and enzymatic analysis. The results showed that SABSL contains glycerol, phosphate, glycerophosphate, d-galactose and d-glucose. d-Galactose and d-glucose accounted for 4.7% and 0.1% of the composition, respectively. Melibiose, but not mannose, inhibited the precipitation reaction. Intense precipitation reactions were obtained with fractions which did not bind to the ConA-column. These results indicate that the immunodominant component of the SABSL is galactose and the SABSL determinant is most probably a galactosylated glycerol teichoic acid. The antiserum raised against the beer spoilage strain L. brevis 578 could distinguish between Pediococcus beer spoilers and non-spoilers in precipitation reactions.