Phenotypic and Genotypic Identification of the Most Acidifiers LAB Strains Isolated from Fermented Food

Over 18 strains of lactic acid bacteria "LAB" isolated from different traditionally fermented products mainly sourdough and fermented vegetables, have been investigated for their lactic bacterial activity. The phenotypic characterization based on their cell morphology, physiological tests and followed by a confirmation test using the commercial carbohydrate fermentation test "API 50 CHL." The phenotypic tests revealed that the strains KA13, KA14, KA24 and KA25 are the fast acidifiers. However, all strains can grow at temperatures ranging from 10 to 37 degrees C, NaCl concentrations ranging from 2 to 6.5% and in a wide pH range from 4 to 9.6. They can use a wide range of carbohydrates as sole carbon source. However, they do not tolerate temperatures above 44 degrees C. The phenotypic identification using API 50 CHL showed that two strains KA13 and KA14 belong to genus Lactobacillus and more specifically to Lactiplantibacillus plantarum, while KA24 and KA25 belong to the genus Leuconostoc. The similarity between "Leuconostoc" species and heterofermentative lactobacillus especially "Levilactobacillus brevis" is essentially due to their common shape, their optimal temperature growth and their end products issue after the glucose metabolism pathway. The genotypic characterization of LABs was carried out on the sequencing of the 16S rRNA gene and its phylogenetic analysis. Phylogenetic analysis showed that KA24 and K25 belong to the genus Levilactobacillus, and they were grouped together with Levilactobacillus brevis ATCC 14869(T) and they share with it 99.93-99.86% of similarities. The strain KA13 belong to the genus Lactiplantibacillus and share 99.79% of similarity with Lactiplantibacillus plantarum NRRL B-14768(T) and Lactiplantibacillus pentosus JCM 1558(T).