Magnetic nanoparticles as support for cellulase immobilization strategy for enzymatic hydrolysis using hydrothermally pretreated corn cob biomass

Abstract

Enzymatic hydrolysis is a key process for lignocellulosic biomass conversion; a way to increase its efficiency and lessen the process cost is by targeting alternative strategies to improve the use of cellulolytic enzymes. This work addresses enzyme immobilization as a strategy to enhance lignocellulosic biomass hydrolysis by simplifying enzyme recovery and opening possibility for continuous processes. Magnetic nanoparticles hold the advantage of easy separation compared to other immobilization supports. Hence, a cellulase cocktail was successfully bonded onto chitosan coated magnetic nanoparticles reaching 65 mgprotein per g of support. The biocatalyst was stable at 4 \textdegreeC after 30 days storage maintaining 80\% of the initial activity and could be reused up to 13 cycles retaining 48.8\% of the initial activity. Considering the information available on corn cob processing, it was used as model biomass for evaluating the efficiency of the system proposed. Corn cob was submitted to a hydrothermal pretreatment at 211 \textdegreeC and non-isothermal regime for biomass fractionation. The pretreated corn cob solid rich in cellulose (61.17 g per 100 g of raw material) was used as substrate [5\% (w/v) solid loading] to evaluate the hydrolysis potential of the immobilized cellulase, obtaining 21.84 g/L of glucose which corresponds to 64.45\\% conversion yield. Thus, this work validates the use of immobilized cellulase cocktails to effectively hydrolyze lignocellulosic substrates, a step-forward in lignocellulosic biorefineries and enzyme reusability. Moreover, the magnetic properties of the support make it a promising technique for eventual continuous operation, an important contribution for cost reduction of the process.