Beer spoilage and low pH tolerance is linked to manganese homeostasis in selected Lactobacillus brevis strains.

Abstract

Beer is a harsh medium for bacteria to survive, however, lactic acid bacteria including Lactobacillus brevis have evolved the ability to grow in beer. Here, the influence of environmental factors such as low pH, ethanol or hop content was assessed. A transcriptomic analysis of two Lact. brevis beer-spoiling strains was performed comparing growth in nutritive media with or without the imposition of a stressor related to the beer environment. This allowed the identification of a manganese transporter encoding gene that contributes to low pH tolerance. We report on the importance of a manganese transporter associated with pH tolerance and beer spoilage in Lact. brevis. The importance of manganese for Lact. brevis growth in a low pH environment was highlighted. Bacterial spoilage of beer may result in product withdrawal with concomitant economic losses for the brewing industry. A limited number of genes involved in beer spoilage have been identified but none of them are universal. It is clear that other molecular players are involved in beer spoilage. The study highlights the complexity of the genetic requirements to facilitate beer spoilage and the role of multiple key players in this process.