Adsorption and activities of lipases on synthetic beidellite clays with variable composition

Synthetic beidellite clays with variable Si/Al ratio in the tetrahedral layers were prepared by hydrothermal crystallization in an acid fluoride medium. The clay materials were characterized by powder-XRD, MAS NMR, BET specific area surfaces and chemical analysis. These samples were used as support for the immobilization of lipase B from Candida antarctica and lipase from Burkholderia cepacia by adsorption. The amount of lipase immobilized on the clay surface increased with decreasing level of aluminium substitution in the tetrahedral layer. The immobilization percentage was significantly higher for CALB (even for three times in the case of high siliceous clays) than those of BCL, when a sample of clay with the same composition is used as support. The catalytic properties of supported enzymes were investigated using the transesterification of vinyl acetate with I-octanol as test reaction. The specific activity of the immobilized lipases depends on both the clay composition - the samples with low content of aluminum exhibited the highest specific activity-, and the amount of adsorbed enzyme - it increases as the amount of enzyme decreases. Also, the catalytic activity of lipase deposited on H+-beidellite is higher than those of enzyme deposited on the Na+ form.