Sourdough is a flour and water mixture fermented by lactic acid-producing bacteria (LAB) and yeasts. Fermenting sourdough positively influences the dough’s properties by improving its volume, texture, and flavor. In Korea, a traditional sourdough has been used to make a sponge-like cake. To prepare the sourdough, nuruk, a wheat flour preparation that is inoculated with environmental microorganisms is mixed with rice (or wheat) flour and incubated. To date, there have been few experimental studies carried out to isolate and characterize LAB from Korean sourdough. Therefore, the aims of this study were the LAB diversity analysis of Korean traditional sourdough and characterization of isolated strains for development of starter cultures for sourdough production. For this, the microbial diversity was analyzed in fermented products as well as raw materials during fermentation of Korean sourdoughs by employing genotypic (RAPD-PCR, RT-qPCR, PCR-DGGE) and phenotypic (VITEK2 Compact system) methods. First, a quantitative assay using a real-time polymerase chain reaction (RT-qPCR) method was developed. Several primers were designed to detect individual species, based on the sequence information obtained from National Center for Biotechnology Information (NCBI). It was demonstrated that each primer set bound to its target microorganisms without cross reactivity. The newly developed method showed a strong correlation with the result obtained by a colony-forming counting method. As results, Lactobacillus sanfrnaciscensis was the most dominant species, representing 56% of the isolates followed by Lb. curvatus (27%) and Lb. brevis (9%). LAB such as Lb. plantarum, Lb. sakei and Pediococcus pentosaceaus were also detected. Next, genotyping and phenotyping analyses at the strain level demonstrated that Korean sourdough possesses various biotypes of L. sanfranciscensis strains. These strains were clustered into 5 subtypes (genotyping) or 7 subtypes (phenotyping). In summary, this strategy to construct novel primers reduced the chance of cross amplification and was able to identify the desired strain. The various strains isolated in this study can be used to develop a sourdough starter after analysis of their fermentation characteristics.

Isolation and characterization of lactic acid bacteria from naturally fermented Korean sourdough

253rd National Meeting (2017)

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