Recherche de nouveaux actifs d'origine microalgale d'intérêt en dermocosmétique : antiacnéens et conservateurs potentiels

摘要

Microalgae are well-known to produce many bioactive molecules which are used more and more in both pharmaceutical and agroalimentary companies. The aim of my PhD project was to discover antimicrobial activitiesof natural origin which may be used in cosmetic in particular as preservatives and antiacne. Culture media in stationary phase of growth of a 113 microalgae collection, cultivated in the laboratory, were harvested. The presence of antibacterial and / or antifungal activities was evaluated on different microorganisms. This screening allowed to isolate 5 microalgae secreting molecules inhibiting the growth of bacteria belonging to Salmonella, Staphylococcus and Propionibacterium genera. Then my work concerned the S555 microalgae which show a total inhibiton activity of the growth on 3 Gram + bacteria : S. aureus, S. epidermis and P. acnes, these 2 last species being involved in the acne disease. This microalgae was then cultivated in industrial condition in order to confirm these inhibitions. A widening of the action spectrum suggests that these activities are specific to Gram + bacteria. Moreover, the S555 active compound(s) present no cytotoxicity or irritability potential on fibroblasts in vitro,making them potentially usable in dermocosmetic. Lastly, a fractionation of the culture medium and biomass of S555 microalgae were performed to separate the active compound(s). Their characterization is currently in progress.