ビール混濁性を示すLactobacillus paracollinoidesおよびL. lindneriからの難培養株の取得

Abstract

Beer spoilage Lactobacillus paracollinoides and L. lindneri strains were repeatedly subcultured in degassed beer and the culturability of these Lactobacillus strains was periodically examined on MRS agar. As a consequence, L. paracollinoides JCM 11969T and LA 4 progressively exhibited diminished culturability on MRS agar, and after the 70 th and 60 th subcultures, respectively, most of the viable cells were no longer detectable on the agar. Similarly, L. lindneri DSM 20692 and HC 92 gradually lost culturability, and after the 70 th and 40 th subcultures, respectively, these strains exhibited viable but nonculturable (VNC) characteristics on the agar. These results suggested that the prolonged adaptation to beer and related environments reduces the culturability of beer spoilage Lactobacillus strains on detection media, posing a threat to the brewing industry. Strikingly, the majority of nonculturable cells, as counted by esterase staining, showed beer spoilage ability, suggesting that microbiological incidents can occur without the detection of beer spoilage lactic acid bacteria on culture media. Taken collectively, these findings indicate that the risk presented by these microorganisms should be nullified by the use of sufficiently robust quality assurance approaches to ensure product stability.