Leuconostoc mesenteroides in the brewing process: A controversial role

The aim of this study was to characterize 29 Leuconostoc mesenteroides isolates obtained from a brewing process in order to determine their potential contributions to this process and the product. In order to achieve this aim different enzymatic activities, the exopolysaccharide (EPS) production, the antagonistic activity, the beer spoilage ability and the production of lactic acid and diacetyl in beer, were assessed. Ln. mesenteroides isolates showed weak acidifying activity, and only 28% of them produced decreases in pH higher than 0.5 units after a 24 h period of incubation. The isolates were also scarcely proteolytic and did not produce EPS. Results from enzymatic activity assay showed that some of the isolates produced beta-galactosidase and alpha- and beta-glucosidases while none produced beta-glucuronidase. All the isolates inhibited the growth of both Escherichia coli and Staphylococcus aureus, although none of them inhibited Pediococcus acidilactici. When Lactobacillus brevis was used as an indicator, 44.8% of the isolates showed antagonistic activity. The beer-spoilage ability assay showed that only 5 of the 29 isolates were able to grow in beer but none of them harboured horA or horC genes. However, the growth of these isolates in beer did not produce an excess of D-lactic acid or diacetyl. These findings show that the presence of any of the characterized isolates during the brewing process or in the bottled beer would not have a negative impact. On the contrary, the findings reveal interesting and potentially beneficial effects. (C) 2018 Elsevier Ltd. All rights reserved.