Detection of beer-spoilage Lactobacillus brevis strains by reduction of resazurin

Lactobacillus brevis is the most common beer-spoilage bacteria found in breweries. Due to its high prevalence and biodiversity, it is necessary to differentiate between the strains based on their hop tolerance. Forcing tests are often conducted for different types of beer, which can vary in cereal base, fermentation type, ethanol- and hop content. These conventional tests are considered to be the safest way to determine the ability of a given strain to cause beer-spoilage, but they are very time consuming and costly. Since NADH₂ is used as cofactor by many cellular dehydrogenases, this study used the reduced form of intracellular nicotinamide adenine dinucleotide (NADH₂) as an indicator for microbial metabolic activity and thus ability to spoil beer, in order to reduce the time required to conduct the forcing tests for beer production. Beer-spoiling L. brevis strains were detected among other strains in beer samples within two days (of sampling).