Faujasite Na-X zeolite as a novel carrier for cellulase immobilization and application in biomass saccharification

As a sustainable and eco-friendly alternative to conventional chemical catalysis, the immobilization of enzymes has been advocated as an attractive strategy to offset the limitations of single-use and rapid loss of activity. The present study aimed to investigate an inert inorganic material, i.e. Na-X zeolite derived from fly ash as a solid carrier for the immobilization of cellulase, a pivotal enzyme for biomass valorization. The cellulase enzyme (Cellic CTec2) was covalently immobilized over Na-X zeolite using glutaraldehyde as a cross-linking agent with immobilization efficiency and yield of 73% and 77%, respectively. The immobilized cellulase exhibited better pH stability (5.0-9.0), temperature optima of 60 degrees C, and a three-fold half-life (t1/2) enhancement at 60 degrees C than its free counterpart. The immobilized preparation retained > 80% residual activity after 5 repeated cycles of usage and had enhanced shelf life, as reflected by good storage stability at both 4 degrees C and 22 degrees C after 4 weeks of in-cubation. The immobilized formulation was utilized to saccharify alkaline pretreated wheat straw to demonstrate its potential for biorefinery applications, and structural deconstruction was validated by SEM, XRD, and FTIR analysis. The high reducing sugar yield for two consecutive cycles confirms its suitability for continuous oper-ation in hydrolyzing lignocellulosic substrates.

Automated summary

This study investigated the immobilization of cellulase using Na-X zeolite derived from fly ash as a solid carrier. The immobilized cellulase showed improved pH stability, temperature optima, and half-life compared to the free enzyme. The immobilized preparation also exhibited good storage stability and was successfully applied in the saccharification of wheat straw.