Hop resistance in beer spoilage lactic acid bacteria (LAB) and other related quality assurance issues - a review

摘要

Lactic acid bacteria (LAB) are predominant beer spoilers and reported to cause 60-90 % of the microbiological incidents. Among numerous LAB species described to date, only a small portion of LAB species are capable of growing in beer and intra-species differences in beer spoilage ability are well known. Hop-resistance ability is a distinguishing character for these beer spoilage LAB strains and constitutes a major quality control (QC) issue in the brewing industry. Hop resistance of beer spoilage LAB has been known as complex phenomena, provided by multidrug transporters and proton-translocating ATPase that counteract the protonophoric actions of hop bitter acids. To supply energy sources for these defense systems, metabolism of organic acids and arginine is involved in beer. Recently these hop-resistance mechanisms have been implicated in larger quality assurance issues concerning beer spoilage LAB, such as the induction of viable but nonculturable (VNC) states and the deteriorated membrane filter performance. These two QC issues, caused by physiological and morphological changes in beer spoilage LAB, pose a serious threat to the brewing industry and appear to be linked to the elevated hop-resistance mechanisms occurring in beer adaptation of LAB. In this review, the issues surrounding microbiological QC problems will be described in one big picture.