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

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.This study was supported by the Portuguese Foundation for Science and Technology (FCT) under the scope of the strategic funding of UIDB/04469/2020 unit. Elisa Zanuso is recipient of a PhD fellow ship supported by the Mexican Science and Technology Council — Energy Sustainability Fund of Secretary of Energy Mexico (CONACY SENER) (CONACYT ID 639021/495314)