Three different polyethylene glycol (PEG) esters of 1:1 fatty acid mixture of ricinoleic, oleic, and linseed oil fatty acids, as eco-friendly nonionic antifoaming biosurfactants were synthesized using a solventless biocatalytic route, to overcome challenges associated with chemical processes. Immobilized lipase Candida antarctica (NS 435) was found to be more effective as a biocatalyst (10 % w/w) than Rhizomucor meihei (RMIM), and Thermomyces lanuginous (TLIM) and led to the highest percentage of fatty acid conversion ∼97.5–98.5 %. The reusability of lipase enzymes was studied, and it has been found that the catalytic activity of NS 435 lipase remained almost intact up to the ninth successive cycle and gradually reduced by 4–5 % thereafter. Whereas RMIM and TLIM were effective till 5 and 4 cycles respectively. The produced esters were characterized, evaluated, and compared for surface activity, emulsification, and antifoaming properties against commercially available nonionic surfactants. The results revealed that the synthesized PEG esters have higher thermal stability, better emulsifying, and excellent antifoaming properties than conventional nonionic surfactants. Thus, the synthesized PEG esters have shown great potential to be used as environment-friendly (>90 % biodegradability) nonionic antifoaming biosurfactants to prepare emulsifiable industrial fluids.
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