Amide Modification of Glycolipid Biosurfactants as Promising Biocompatible Antibacterial Agents

Discovering new antibacterial agents is crucial to addressing the increasing risk of bacterial infections induced by antimicrobial resistance in food and agricultural industries. Here, biocompatible acidic-type sophorolipids (ASLs) and glucolipids (GLs) prepared via chemical modification of natural sophorolipids from fermentation were functionalized via amide modification for use as potential antibacterial agents. It was found that the arginine methyl ester derivative of GLs (GLs-d-Arg-OMe) showed excellent antibacterial activity, killing more than 99.99% of Escherichia coli at 200 mg/L. The sterilization dosage of the GLs against Bacillus subtilis, Bacillus cereus, and Staphylococcus aureus was 16-64 mg/L, in contrast to 32-64 mg/L for the fungus Candida albicans. In particular, GLs-d-Arg-OMe showed the best biocompatibility with a therapeutic index of up to 18. It was shown that amide modification of glycolipids can effectively improve antibacterial activity while maintaining biocompatibility, which can be exploited for the development of novel antibiotics in food and agricultural fields.