Identification of Lactic Acid Bacteria Strains Isolated from Sourdoughs Prepared with Different Flour Types

Abstract

Species identification is the first step in the examination of newly isolated microorganism strains, including the cases when they are intended for application in the development of probiotic preparations or starters for different food products. The thorough identification process of newly isolated strains combines the application of different physiological, biochemical, and molecular genetic methods. The aim of the present study was to identify the species-level lactic acid bacteria (LAB) strains isolated from spontaneously fermented sourdoughs prepared from different flour types: Khorosan wheat, wheat, barley, buckwheat, spelled, spelt, and corn. Both classical phenotypic (cellular morphology characterization, and API 50 CHL) and molecular genetic methods (RAPD, ARDRA-analysis, 16S rDNA sequencing, and species-specific PCR) were applied. It was found that cultures with a short-rod morphology predominated among the 30 sourdough isolates. According to the RAPD profiles obtained, the isolates were divided into nine genotypes corresponding to nine genetically distinct strains. It was determined that individual sourdoughs made with different flour types shared cultures with a common genotype. The analysis of the physiological and biochemical profiles of the LAB isolates performed with the API 50 CHL system divided them into two groups according to their identification: Lactiplantibacillus plantarum (Lp. plantarum) 1 and Levilactobacillus brevis (Lv. brevis) 3. According to the 16S rDNA restriction profile, the LAB isolates showed two profiles corresponding to the Lp. plantarum and Lv. brevis groups. 16S rDNA sequencing and a comparison of the partially read 16S rDNA sequences of the studied isolates confirmed that some of them belonged to the Lv. Brevis species, but did not provide sufficient evidence that the rest of the cultures belonged to the Lp. Plantarum species. The species-specific PCR clearly separated the isolates from the Lp. plantarum group into two groups: isolates of the Lp. plantarum species and isolates of the Lp. paraplantarum species. The summary of the results of the conducted polyphasic taxonomic study determined the investigated LAB strains isolated from spontaneously fermented sourdoughs as representatives of the Lv. brevis, Lp. plantarum ssp. paraplantarum, and Lp. paraplantarum species.