Antimicrobial activity of sophorolipids derived from yeast Starmellela riodocensis strain GT-2564R against Escherichia coli

Sophorolipids (SLs), a type of glycolipid biosurfactant, are primarily produced by non-pathogenic yeast species, such as Starmellela riodocensis strain GT-2564R in abundance yield. SLs represent one of the biosurfactants in the industry due to their antimicrobial action against both Gram-positive and Gram-negative bacteria as well as other pathogens. This study is the first report of antimicrobial activity of SLs produced from S. riodocensis against Escherichia coli, from the yeast strain GT-2564R, using the green extraction methods and the welldiffusion assay. The results demonstrated that crude SLs with a concentration of 1,00 µg/mL from the yeast strain GT-2564R can inhibit the growth of E. coli, with an inhibition zone of 2.0 ± 0.08 cm. Especially, SLs extracted with a green solvent including Choline chloride: urea + Ethyl acetate (1:9 v/v), Choline chloride: glycerol + Ethyl acetate (1:9 v/v), and sole Ethyl acetate can kill E. coli with Minimum Bactericidal Concentraction (MBC) values of 500, 62.5, and 31.25 µg/mL, respectively. These findings underscored the potential application of SLs as valuable antimicrobial agents and open up new avenues for their production and future applications in various industries, such as in pharmaceuticals and in food secments as natural food preservation.