Roles of mannosylerythritol lipid-B components in antimicrobial activity against bovine mastitis-causing Staphylococcus aureus

Abstract

Mannosylerythritol lipid-B (MEL-B), which comprises ester-bonded hydrophilic ME and hydrophobic fatty acids, is a bio-surfactant with various unique properties, including antimicrobial activity against most gram-positive bacteria. The gram-positive Staphylococcus aureus is a causative pathogen of dairy cattle mastitis, which results in considerable economic loss in the dairy industry. Here, we demonstrate the efficacy of MEL-B as a disinfectant against bovine-derived S. aureus and elucidate a mechanism of action of MEL-B in the inhibition of bacterial growth. The growth of bovine mastitis causative S. aureus BM1006 was inhibited when cultured with MEL-B above 10 ppm. The activity of MEL-B required fatty acids (i.e., caprylic and myristoleic acids) as ME, the component of MEL-B lacking fatty acids, did not inhibit the growth of S. aureus even at high concentrations. Importantly, ME-bound fatty acids effectively inhibited the growth of S. aureus when compared with free fatty acids. Specifically, the concentrations of ME-bound fatty acids and free caprylic and myristoleic acids required to inhibit the growth of S. aureus were 10, 1442, and 226 ppm, respectively. The involvement of ME in the antimicrobial activity of MEL-B was confirmed by digestion of MEL-B with alkali, which dissociated ME and fatty acids. These results indicated that a mechanism of action of MEL-B in inhibiting the growth of S. aureus could be explained by the effective transporting of antimicrobial fatty acids to the bacterial surface via hydrophilic ME.

Unlocking the Potential of Mannosylerythritol Lipids: Properties and Industrial Applications

“…The researchers concluded that MELs exhibit a robust inhibitory effect on Gram-positive bacteria, along with some sensitivity towards Pseudomonas strains. Antimicrobial activity was further studied in the food-borne pathogens S. aureus, Bacillus cereus and Listeria monocytogenes [35][36][37][38]78]. It was observed that MELs' antimicrobial effect was linked to their capacity to damage the integrity of cell membranes.…”

Unlocking the Potential of Mannosylerythritol Lipids: Properties and Industrial Applications

“…The researchers concluded that MELs exhibit a robust inhibitory effect on grampositive bacteria, along with some sensitivity from the Pseudomonas strains. The antimicrobial activity was further studied in the food-borne pathogens S. aureus, Bacillus cereus and Listeria monocytogenes [28][29][30][31]68]. It was observed that MELs antimicrobial effect is linked to its capacity to damage the integrity of cell membranes.…”

Molecular Basis of Yeasts Antimicrobial Activity—Developing Innovative Strategies for Biomedicine and Biocontrol

“…A MEL-B biosurfactant obtained from P. tsukubaensis NBRC1940 acted as a disinfectant agent, inducing inhibition of cell growth of dairy cattle mastitis agents S. aureus, with its activity being correlated with the transportation of fatty acids (caprylic acid and myristoleic acid) with antimicrobial activity to the surface of bacterial cells [187]. On the contrary, the biosurfactant had no effect against Gram-negative bacteria E. coli, although it bounds on the surface of the cell.…”