Abstract
New strains of lactic acid bacteria (LAB) were isolated from different traditional dairy products. Six new strains named Lactobacillus delbrueckii strain A01, Lactobacillus delbrueckii subsp. bulgaricus strain D01, Lactobacillus delbrueckii subsp. bulgaricus strain E01, Lactococcus lactis strain G01, Lactobacillus delbrueckii strain C01, and Lactobacillus delbrueckii subsp. bulgaricus strain F01 were identified using 16S rDNA sequencing, morphological and biochemical traits. All strains have been registered in the National Center for Biotechnology Information (NCBI) with accession numbers MN611241.1, MN611300.1, MN611301.1, MN611303.1, MN611241.1, and MN611299.1, respectively. Having found ε-Poly-L-Lysine (ε-PL) in all strains isolated, Lactobacillus delbrueckii strain A01 was identified as an active producer of ε-Poly-L-Lysine (ε-PL). The one-factor-at-a-time method and central composite design were applied to optimize ε-Poly-L-Lysine (ε-PL). A predicted 200 ppm of ε-PL was obtained in the medium containing the lowest level of glucose, 25 g/l, and yeast extract, 6 g/l.
Highlights
Lactic acid bacteria impart curative properties and antimicrobial activities to dairy products [1]
Colony morphology was initially used to recognize the different types of Lactic acid bacteria (LAB); thereby, bacterial shapes colored by gram staining were microscopically identified
Six strains of LAB isolated from dairy products were identified and published with GenBank accession numbers
Summary
Lactic acid bacteria impart curative properties and antimicrobial activities to dairy products [1]. Various research studies have employed phenotypic characteristics and biochemical properties to identify LAB in dairy products [11], while a PCR-based technique was a more effective way to precisely identify LBA than the conventional methods. Using this reliable method has led to the discovery of various microorganisms all across the world [12]. One of the main reasons why fermented dairy products have had a long shelf life is because of the active components with antimicrobial properties, given that initial experiments conducted in this research revealed that the isolated LAB turned out to be good sources of ε-PL. The strain with the highest potential for producing ε-PL was selected for optimization by using the one-factor-at-a time and RSM methods
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