Specific enumeration of lactic acid bacteria in ragi tape by colony hybridization with specific oligonucleotide probes

Abstract

Lactic acid bacteria (LAB) are among the integral microflora of ragi tape, a dry starter of Balinese rice wine, brem. The species diversity and population level of LAB present in different types of ragi tape were studied by colony hybridization using 16S and 23S rDNA targeted oligonucleotide probes. These probes were DB6, Lbc, Wgp, and Rpt, which were specific for Enterococcus faecium, Lactobacillus curvatus, Weissella spp., and Pediococcus pentosaceus, respectively. Results revealed that P. pentosaceus and Weissella spp. were the predominant LAB in ragi tape, whereas L. curvatus and E. faecium were associated specific to types of ragi tape. A 21-mer species-specific oligonucleotide probe, Rpt, that targets the 16S rDNA of P. pentosaceus was developed in this study and found to be highly specific to be used as an effective tool to enumerate population of this species in ragi tape and its population changes during rice wine production. It was detected that LAB showed active growth during the early stage of brem fermentation. A succession of growth of LAB population during the fermentation was observed in which the heterofermentative LAB, Weissella spp., grew first, followed by the proliferation of P. pentosaceus.