Characterization of bioactive Leuconostoc mesenteroides producing bacteriocin strains isolated from camel’s and goat’s Algerian raw milks

The purpose of this study was to evaluate the ability to produce bacteriocin, the safety, the probiotic and the biotechnological functionalities of a collection of Leuconostoc strains, to be used as adjunct starters in dairy industry. Firstly, Leuconostoc strains were isolated from different Algerian raw camel’s and goat’s milks and subjected to preliminary identification and technological identification characterization. Out of 176 isolates, 110 were selected for technological traits and subjected to molecular identification: 83 isolates were identified as Leuconostoc mesenteroides subsp. mesenteroides (75%), 22 as Leuconostoc mesenteroides subsp. dextranicum (20%) and 5 as Leuconostoc mesenteroides subsp. cremoris (5%). Secondly, 33 strains, exhibiting the highest inhibition effect against indicator bacteria, were selected and identified both at species and subspecies levels by16S rRNA and pulsed-field-gel electrophoresis (PFGE) analyses. Results confirmed the subspecies identification and the clonal relationships among the 33 strains showed 17 genotypes. Based on the highest inhibition effect against indicators such as Listeria monocytogenes, Listeria innocua, Listeria ivanovii, Staphylococcus aureus, Brochothrix thermosphacta, Micrococcus luteus, Lactobacillus sakei, Escherichia coli and Pseudomonas aeruginosa, 5 bioactive L. mesenteroides subsp. mesenteroides strains were selected and subjected to safety, probiotic and technological evaluations. Results showed a low prevalence of antibiotic resistance and significant proteolytic and autolytic activities while only two of them (Ln.O6 and Ln.F5 strains) exhibited lipolytic activity. The strains showed the ability to survive at acidic pH values and in presence of pepsin and bile salts and any production of biogenic amines or DNase were observed. Moreover, any gelatinase or haemolytic activity were recorded. All strains exhibited high production of diacetyl and exopolysaccharide and two of them (Ln.F5 and Ln.M14) were selected for exhibiting the best recorded performances and proposed for further investigation as adjunct cultures in dairy industry.