Immobilization and Performance of Cellulase on Recyclable Magnetic Hydrotalcites

mHT(Zn) and mHT(Mg) hydrotalcites were fabricated by co-precipitation of Zn²⁺/Al³⁺ and Mg²⁺/Al³⁺ salt mixtures in the presence of Fe₃O₄ and used as supports for immobilizing cellulase to form cell@mHT(Zn) and cell@mHT(Mg). The structure and properties of mHT(Zn), mHT(Mg), cell@mHT(Zn), and cell@mHT(Mg) were characterized by Fourier−transform infrared spectroscopy, X-ray diffraction, filtering electron microscopy. The effect of pH, cellulase concentration, and the number of supports on the immobilization of cellulase onto supports were carefully investigated. The enzyme activity of free cellulase, immobilized cellulase, and immobilization efficiency was analyzed by determining reduced glucose using DNS as a color indicator. The highest immobilization efficiency obtained was 94.9 % when carried out on mHT(Zn) at pH 6.5 and 95.3 % on mHT(Mg) and the concentration of cellulase in 0.1mg/mL at the pH of 5.5, using 0.2 g of supports. Cell@mHT(Zn) and cell@mHT(Mg) show high enzyme activity when reacting with 1 % CMC solution at 50 ^oC with relative enzyme activity of 78.0% and 70.4 %, respectively.