Biotechnological potential and genomic analysis of the Leuconostoc mesenteroides F17 and F18 strains isolated from camel milk

Abstract

Camel milk is known for its distinctive nutritional and antimicrobial properties. Thus, it offers a valuable niche for discovering novel probiotic strains with potential health benefits. In this context, two Leuconostoc mesenteroides strains, F17 and F18 were isolated from this dairy matrix and their properties analysed. Also, to gain deeper insight into their probiotic and technological traits, the sequencing of the whole genomes of both strains was conducted, revealing key genetic features supporting their suitability as starter cultures. The two bacteria displayed desirable technological properties including among them rapid milk acidification capability as well as proteolytic and lipolytic activities. F17 and F18 produced riboflavin (0.11 and 0.15 mg/L) and exopolysaccharides (1.8 g/L and 3.7 g/L) characterized as dextran by physicochemical analysis. The F17 and F18 DsrD dextransucrases of ~ 170 kDa, responsible for the dextran synthesis, were visualized by a zymogram analysis and their dsrD coding genes, with 98.99% identity, were identified in their genomes. After 24 h growth in a sucrose-containing medium, analysis of metabolic fluxes in culture supernatants of both bacteria demonstrated accumulation of the sweetener mannitol and the antimicrobial lactic acid; at the levels of 59 mM and 76.57 mM in the case of the best performer (F18). Furthermore, the results demonstrated that both strains exhibited good survival rates under in vitro simulated stomach duodenum-passage. A high surface adhesion was also observed for F17 and F18 including hydrophobicity of 30.15% and 31.72% and auto-aggregation ability of 44.71% and 53.23%, with a good resistance to phenol exposure and to moderated heat shock. As expected from the genomes inspection, the safety analysis revealed that the two strains were susceptible to most of the tested antibiotics, and none of them showed any hemolytic activity or biogenic amines synthesis capability. Both cultures supernatants exhibited significant growth inhibition of foodborne pathogens, presumably due to the present of lactic acid. Thus, these findings suggest that camel milk may harbor lactic acid bacteria with promising technological and probiotic traits, as exemplified by F17 and F18.

Keywords: Leuconostoc mesenteroides; Dextran; Dextransucrase; Lactic acid bacteria; Mannitol; Probiotic; Riboflavin.