Enrichment or dilution methods are generally used for isolating lactic acid bacteria (LAB) from natural samples. However, these methods depend on the microbe's predominant characteristics or growth rate. Here, we developed a new method for isolating minor LAB by co-culture with yeast strains. We then used this method to isolate rare and indigenous species in the traditional fermented foods of Myanmar, thus enabling us to determine the taxonomic diversity of LAB there. To analyze the effects of co-culture we tested a combination of 18 species and 2 subspecies of LAB and 6 species of yeast. Interestingly, some specific combinations either accelerated or suppressed LAB growth. Eight fish or prawn products fermented with rice (ngachin and pazun-chin) were then obtained from the Ayeyawady market in Myanmar for testing. By using co-culture and dilution methods we isolated 52 LAB from these products. Co-culture with yeast resulted consistently in LAB isolation from all samples. The LAB were assigned to 3 genera and 15 species; the genus Lactobacillus accounted for 85% (44 strains) of the bacteria in these products. 16S rDNA analysis showed that one new species candidate was isolated by the dilution method, whereas 2 new species candidates were isolated by the co-culture method. Lactobacillus futsaii and Lactobacillus plajomi, isolated recently from Taiwanese fermented mustard products and from Thai fermented food, respectively, were also detected by the dilution method. However, the genus Weissella was isolated only by co-culture with Saccharomyces cerevisiae. Thus, co-culture enabled the isolation of rare LAB that are otherwise difficult to isolate by using the normal dilution method. Our results suggest that the development of new methodologies for isolating LAB is highly important for expanding our understanding of their ecology, taxonomy, and distribution.
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