Production of Mannosylerythritol Lipids (MELs) to be Used as Antimicrobial Agents Against S. aureus ATCC 6538

Abstract

Antimicrobial resistance (AMR) is a current major health issue, both for the high rates of resistance observed in bacteria that cause common infections and for the complexity of the consequences of AMR. Pathogens like Staphylococcus aureus, Pseudomonas aeruginosa, Klebsiella pneumoniae, Mycobacterium tuberculosis among others are clear examples of antibiotic-resistant threats. Biosurfactants have recently emerged as a potential new generation of anti-adhesive and anti-biofilm agents; mannosylerythritol lipids (MELs) are biosurfactants produced by a range of fungi. A range of structural variants of MELs can be formed and the proportion of each isomer in the fermentation depends on the yeast used, the carbon substrate used for growth and the duration of the fermentation. In order to allow assessment of the possible functions of MELs as antimicrobial molecules, small quantities of MEL were produced by controlled fermentation. Fermentations of the yeast Pseudozyma aphidis using rapeseed oil as a carbon source yielded up to 165 g MELs /kg Substrate. The MELs formed by this strain was a mixture of MEL-A, MEL-B, MEL-C and MEL-D. The MELs produced were tested against S. aureus ATCC 6538 on pre-formed biofilm and on co-incubation biofilm experiments on silicone discs; showing a disruption of biomass, reduction of the biofilm metabolic activity and a bacteriostatic/bactericidal effect confirmed by a release of oxygen uptake p O 2 , the reduction of citrate synthase activity and scanning electron microscopy. The results show that MELs are promising antimicrobial molecules for biomedical technological applications that could be studied in detail in large-scale systems and in conjunction with animal tissue models.

Diverse Effects of Natural and Synthetic Surfactants on the Inhibition of Staphylococcus aureus Biofilm

“…Even if the anti-biofilm activity of glycolipids is well known [ 72 , 76 , 77 , 78 ], in this work, for the first time, the higher anti-biofilm efficiency of rhamnolipids compared to synthetic surfactants was demonstrated. Similar results were reported by Pontes et al [ 79 ] on other glycolipids.…”

Recent Advances in Biomedical, Therapeutic and Pharmaceutical Applications of Microbial Surfactants

“…Mannosylerythritol lipids (MELs), from Pseudozyma aphidis , were also tested against S. aureus biofilm formation and pre-formed biofilms on silicone discs, in co-incubation experiments. The MELs had an interesting ability to inhibit/decrease S. aureus biofilm biomass and metabolic activity by their bacteriostatic/bactericidal effect on sessile cells [ 113 ]. Rhodococcus fascians BD8, isolated from Arctic soil, produced a trehalose lipid with significant antiadhesive properties against Proteus mirabilis , E. coli , Enterococcus hirae , S. epidermidis , E. faecalis , Proteus vulgaris and C. albicans .…”

Surface Active Agents and Their Health-Promoting Properties: Molecules of Multifunctional Significance

“…Their findings show a high potential of MELs as a natural preservative in the food industry. One of the recent studies by Ceresa et al [ 27 ] presented an excellent activity of MELs against a wellknown pathogen Staphylococcus aureus ATCC 6538. The surfactants were efficient at disrupting the S. aureus biomass, reducing the metabolic activity of the biofilm and also showed bacteriostatic and bactericidal properties against the pathogen.…”