Mini-Review: The current role of lactic acid bacteria in beer spoilage

Few bacteria and yeast species are able to tolerate the antibacterial hurdles of beer and change its sensory properties such as smell, appearance, and texture. Tolerance to hop acids in particular is considered to be crucial to the survival of microorganisms in this hostile environment. Thus, the spectrum of beer-spoiling microorganisms is limited, but subject to slight changes in composition. Lactic acid bacteria (LAB) of the Lactobacillus and Pediococcus genera constitute the major part of this restricted group. Depending on their beer-spoilage potential and frequency of occurrence, each beer-spoiling species has its individual hazard potential. This hazard potential characterizes the danger the single species exerts on beer. The most dangerous beer spoiler is still the species L. brevis. It is vital for brewing microbiologists to be up to date with all the species with beer-spoilage ability. In the past decade, two beer-spoiling species, L. cerevisiae and L. curtus, have been newly described and two further species, L. acetotolerans and L. rossiae, were discovered to contain isolates with beer-spoilage potential. The mini-review gives an overview of all currently known LAB species with beer spoilage potential highlighting their species specific traits and their distribution in brewing environment. In addition to the species-specific approach, brewing microbiologists focus on species-independent strategies to reliably detect single isolates with beer-spoilage potential. A promising approach is the examination of genes located on mobile genetic elements such as plasmids that constitute a large portion of the beer-spoilers' genomes and are taken up by horizontal gene transfer.