Immobilized lipases in sericin–dimethylolurea films as biocatalysts in esterification

Abstract

This study reports on the synthesis and characterization of sericin–dimethylolurea films (SS–DMU) and the immobilization of Burkholderia cepacia LTEB11 lipases through the so-called “sandwich” adsorption method, wherein the enzyme is deposited on the film, forming an enzyme–film–enzyme surface. Measured film thicknesses were between 230 and 309 μm. Resistance to traction was approximately double in comparison to the film with no enzyme applied. Scanning electron microscopy images attest the formation, after the enzyme immobilization, of aggregate deposits, possibly proteins, over the film surface. Catalytic efficiency was ascertained in ethyl oleate esterification reactions. Ester yield was practically equal (96%, 24 h) for the free and immobilized enzymes. Film samples with different quantities of lyophilized enzyme deposits (56, 122 and 156 mg) were analyzed; during the first 5 h of observation the sample with the largest quantity showed faster reaction speeds. The immobilized lipase (56 mg) was reused, and catalytic efficiency decreased to 58% after seven reaction cycles. The results point to SS–DMU film as a promising biocatalysis material.