Hemp tea waste-immobilized lipase for the synthesis of alkyl oleates in solvent free systems

This study explores the immobilization of lipase from Candida rugosa (CRL) on hemp tea waste to catalyze the esterification of oleic acid with primary aliphatic C2-C12 alcohols in a solvent-free system. The immobilization method employed was adsorption, chosen for its simplicity, low cost, and ability to preserve enzyme activity. The esterification of undecanoic acid, lauric acid, and oleic acid with alcohols of varying chain lengths (ethanol, 1-propanol, 1-butanol, 1-octanol, 1-decanol, and 1-dodecanol) was studied. The esterification efficiency was found to be influenced by the type of alcohol, the molar ratio of oleic acid to alcohol, and the water content in the reaction medium. The highest conversions were achieved with ethanol (23 % conversion with 18.5 % water and a molar ratio of 1:5) and 1-decanol (30 % conversion with no added water and a molar ratio of 1:2). Comparatively, the soluble lipase achieved slightly higher conversion of oleic acid using decanol (38 %), indicating that the performance may be attributed to origin of lipase, rather than the immobilization procedure. The study demonstrated that the immobilization of lipase on hemp tea waste did not hinder enzyme activity. Additionally, the biocatalyst developed can function in a completely solvent-free system, offering a green solution by repurposing waste materials for industrial ester production.