Study on molecular identification of lactic acid bacteria from fermented milks and “Smen” (a traditional steppe butter) and their enzyme producing attributes

Abstract

Streptococcus thermophilus and Lactobacillus belong to a widely-knowngroup of bacteria that have been frequently used as starter bacteria in fermented dairy products. The aim of this study was to isolate, characterize andidentify of lactic acid bacteria (LAB) from raw cow’s fermented milk and‘Smen’ (a traditional steppe butter) in steppic area of Algeria to study someof their important enzyme-producing attributes. All selected strains of lacticacid bacteria (LAB) were identified and typed by phenotypic and genotypiccriteria.Six strains were identified as cocci thermophilic LAB and two of themwere selected and identified by using polymerase chain reaction (PCR) amplification for proA gene. Six strains of lactobacilli were identified as Lactobacillus genus using 16S rRNA gene. Species identification was performed by 16SrRNA gene sequencing and sequences were analysed using Basic LengthAlignment Search Tool (BLAST) programs. A phylogenetic tree based on 16SrRNA genes was constructed by the neighbor-joinin method.S. thermophilusstrains screened for their ability to produce lactic acid, titratable acidity, andpH was measured at 2h intervals, proteolytic activity in milk was examined.In another part, the four selected Lactobacillus were able to hydrolyze X-Galby production of β-galactosidase enzyme. All strains of LAB exhibited production of diacetyl. Overall, this study provides bacterial strains having potentialfor dairy industry.