Immobilization of lipase on spent coffee grounds by physical and covalent methods: A comparison study

Spent coffee grounds were treated to obtain suitable carriers for both physical and covalent immobilization of Candida rugosa lipase. In the first case, physical adsorption was directly performed after water/organic solvent extraction of the interferents from the support, while in the second case the delignification and the activation of the support with glutaraldehyde or KIO4 were necessary. The support materials obtained were characterized by Fourier transform attenuated total reflection IR, elemental analysis, and scanning electron microscope. Each immobilization method was investigated to obtain the best insoluble biocatalyst immobilized activity, efficiency, and recovery. Emphasis was given to the study of the water/organic solvent ratio in the immobilization mixture as it has proven to be a decisive parameter. The optimized immobilized biocatalyst obtained by adsorption mechanism showed up to 33 U g-1 of immobilized enzyme activity, and a higher pH, thermal, and storage stability than the free lipase. This solid biocatalyst also preserved 100% of its activity after four recycles in p-nitrophenyl palmitate hydrolysis in hexane medium and permitted an almost 60% conversion of milk fats in fatty acids after 18 h of reaction, maintaining this value for three reuses.