Corn Straw Residue: a Strategy for Lipase Immobilization.

ABSTRACT

This work aims to study the immobilization of Candida rugosa lipase (CRL) onto corn straw residue. For this purpose, chemical, morphological, and textural characteristics of the corn straw; immobilization process by adsorption; and immobilized enzyme activity and storage stability were evaluated. The corn straw presented isoelectric point of 7.0, surface with hydroxyl bands being favorable to the immobilization process. An irregular surface was also observed with fibers and pores, which are mesoporous and macroporous, characteristics that demonstrate efficiency in mass transfer mechanisms. Upon immobilization, it was observed that adsorption velocity is proportional to the square of the available adsorption sites (pseudo-second-order), and that the immobilization occurs in monolayers (Langmuir isotherm). The adsorption process was favorable and considered as a chemical adsorption mechanism. After immobilization, the optimum temperature increased, the optimum pH reduced, and the affinity of the biocatalyst for the substrate decreased. Corn straw derivative demonstrated good thermal stability. Regarding storage stability, there was approximately 12% loss of activity after 60 days of storage at 4 °C. Considering that no treatment was applied to the corn straw, this result is satisfactory and shows good affinity between this support and CRL.