Zirconium phosphate and modified zirconium phosphates as supports of lipase. Preparation of the composites and activity of the supported enzyme

Biocomposites with enzymatic activity were obtained by adsorption of lipase from Candida rugosa on the surface of different layered zirconium phosphates and phosphonates such as cc-zirconium hydrogen-phosphate, solid dispersions of zirconium phosphate in silica, zirconium carboxyethanephosphonate, zirconium phosphate-carboxyethanephosphonate, zirconium benzenephosphonate, and zirconium phosphate-benzenephosphonate. All the supports were characterized for chemical composition, BET specific surface, area, surface ion exchange capacity, and X-ray diffraction patterns. The adsorption process at 4 degreesC was studied as A function of time of equilibration of the support with the lipase solutions (0.5 mg/mL) and as a function of the amount of protein present in the equilibrating solution. The activities of biocomposites with the different supports, at different protein loadings, were obtained by determining the amount of acetic acid produced by catalyzed hydrolysis of p-nitrophenylacetate. The best results in terms of protein surface adsorption (29 mg of protein/g of support) and of catalytic efficiency (95%) were achieved with hydrophobic supports based on zirconium benzenephosphonate. The biocomposites can be stored for more than one month at 4 degreesC without loss of enzymatic activity, have been used in several cycles, and undergo limited thermal degradation when used at 40 degreesC.