Glutaraldehyde activation of polymer Nylon-6 for lipase immobilization: Enzyme characteristics and stability

An extracellular alkaline lipase of a thermo tolerant Bacillus coagulans BTS-3 was immobilized onto glutaraldehyde activated Nylon-6 by covalent binding. Under optimum conditions, the immobilization yielded a protein loading of 228 mu g/g of Nylon-6. Immobilized enzyme showed maximum activity at a temperature of 55 degrees C and pH 7.5. The enzyme was stable between pH 7.5-9.5. It retained 88% of its original activity at 55 degrees C for 2 h and also retained 85% of its original activity after eight cycles of hydrolysis of p-NPP. Kinetic parameters Km and V a were found to be 4 mM and 10 mu mol/min/ml, respectively. The influence of organic solvents on the catalytic activity of immobilized enzyme was also evaluated. The bound lipase showed enhanced activity when exposed to n-heptane. The substrate specificity of immobilized enzyme revealed more efficient hydrolysis of higher carbon length (C-16) ester than other ones. (C) 2007 Elsevier Ltd. All rights reserved.