Wealth from waste: Multifaceted yeast bio-synthesised sophorolipids using industrial waste by-products as substrate

Abstract

Sophorolipid biosurfactants are known for their versatile biological and physicochemical activities. This study explores its production, characterization, and biological activities utilising, palm fatty acid distillate (PFAD), a hydrophobic substrate derived from oil refinery waste by Starmerella bombicola, a native sophorolipid producing yeast. The sophorolipid yield is significantly enhanced by using PFAD than that of a vegetable oil used as feedstock. The yields are 36.71 and 18.62 g/L for PFAD and refined sunflower oil, respectively. The minimum surface tension with PFADSL (palm fatty acid distillate derived sophorolipid) is 37.73 mN/m and the CMC value is 76 mg/mL. Emulsifying properties of PFADSL are found to be 54.32%, 59.45%, and 28.38% for waste frying sesame oil, refined sesame oil, and petrol, respectively. The PFADSL is characterized using TLC, FTIR, and HPLC confirming the major component to be diacetylated lactonic sophorolipids (SLs) (C18:1) consisting 15.4% acidic forms ofsophorolipids. PFADSL showed minimum inhibitory concentration values ranging between 25 - 50 μg/mL against Proteus vulgaris, Shigella flexneri, Salmonella typhi, Vibrio cholerae, Staphylococcus aureus, Escherichia coli, Bacillus subtilis, and Klebsiella pneumoniae. Minimum Bactericidal Concentrations range from 300 to 500 μg/mL. SEM images show compromised membrane integrity against both gram-negative and positive bacteria. PFADSL also confirmed its strong biofilm inhibitory and eradication capacity against tested organisms. These findings reveal a noteworthy way of bio-converting oil industrial waste into a valuable product with potent surface lowering, emulsifying, antibacterial, and antibiofilm ability which can be a gem to various fields like biomedical, agricultural, pharmaceutical, cosmetics, nanotechnology, etc.