Preparation and Evaluation of Coal Fly Ash/Chitosan Composites as Magnetic Supports for Highly Efficient Cellulase Immobilization and Cellulose Bioconversion

Abstract

Two magnetic supports with different morphologies and particle sizes were designed and prepared for cellulase immobilization based on chitosan and industrial by-product magnetic coal fly ash (MCFA). One was prepared by coating chitosan onto spherical MCFA particles to form non-porous MCFA@chitosan gel microcomposites (Support I) with a size of several micrometers, and the other was prepared using the suspension method to form porous MCFA/chitosan gel beads (Support II) with a size of several hundred micrometers. Cellulase was covalent binding to the support by glutaraldehyde activation method. The morphology, structure and magnetic property of immobilized cellulase were characterized by scanning electron microscopy, Fourier transform infrared spectroscopy and a vibrating-sample magnetometer. The cellulase loading on Support I was 85.8 mg/g with a relatlvely high activity recovery of 76.6%, but the immobilized cellulase exhibited low thermal stability. The cellulase loading on Support II was 76.8 mg/g with a relative low activity recovery of 51.9%, but the immobilized cellulase showed high thermal stability. Cellulase immobilized on Support I had a glucose productivity of 219.8 mg glucose/g CMC and remained 69.9% of the original after 10 cycles; whereas the glucose productivity was 246.4 mg glucose/g CMC and kept 75.5% of its initial value after 10 repeated uses for Support II immobilized cellulase. The results indicate that the two supports can be used as cheap and effective supports to immobilize enzymes.

Preparation of Chitosan/Magnetic Porous Biochar as Support for Cellulase Immobilization by Using Glutaraldehyde

“…As shown in Figure 5 , the C–O stretching vibration of the porous biochar was found at 1100 cm −1 [ 44 ]. For the biochar/γ-Fe 2 O 3 @chitosan, the methylene stretching vibrations at 2924 and 2856 cm −1 were attributed to the chitosan layer [ 45 ]. Moreover, amide II stretching vibrations of the cellulase at 1648 and 1560 cm −1 were found in the immobilized enzyme, which suggests that the cellulase was successfully immobilized onto the support.…”

“…In addition, the immobilized cellulase showed higher relative activity than the free cellulase at pH 3. Under acidic conditions, the protonation of chitosan was easy and it was possible to interact with more CMC [ 45 ]. This means that during the hydrolysis process, the CMC concentration around the immobilized enzyme could have been higher than that of the free one at a lower pH, which could have promoted the hydrolysis process.…”

“…The increase in K m and the decrease in V max indicates that the binding tightness between the immobilized enzyme and substrate decreased compared to that of the free enzyme. This is because of the steric hindrance generated by the support [ 45 ].…”

An overview of biomass conversion: exploring new opportunities

“…Several methods have been developed to immobilize cellulase enzymes. The results indicate that cheap supports can be used to effectively immobilize enzymes (Zang et al, 2018).…”

Recent Advances of Cellulase Immobilization onto Magnetic Nanoparticles: An Update Review

“…Thus, the covalent binding using cross-linkers is widely applied to resolve this problem. Among the cross-linkers, glutaraldehyde is commonly employed as the coupling agent for covalent cellulase immobilization to the support since it is soluble in aqueous solvents and provides firm inter-and intra-covalent bonds [45][46][47][48][49].…”