The Study of the Characteristics and Hydrolysis Properties of Naringinase Immobilized by Porous Silica Material

Silica material has high specific surface area and excellent chemical stability, which make it useful for enzyme immobilization. In this work, naringinase was immobilized from fermentation broth of Aspergillus niger FFCC uv-11 by silica materials with different pore diameters of 2 nm (MCM-41), 7.7 nm (SBA-15) and 80 nm (silica gel). It was shown that SBA-15 had the highest naringinase activity, and this was chosen as a suitable carrier material for naringinase immobilization. First, SBA-15 was modified by glutaraldehyde at a concentration of 7% at 25 degrees C for 2 h, and it was then used for the immobilization of naringinase. At pH 3.5, the immobilized naringinase activity reached 467.62 U g(-1) at 40 degrees C for 4 h when the initial naringinase activity was 89.04 U mL(-1). Furthermore, at the optimal reaction temperature of 45 degrees C and pH of 4.5, the binding efficiency, activity recovery rate and specific activity of the immobilized naringinase were 63.66%, 87.64% and 517.43 U g(-1), respectively. Compared with free naringinase, in naringin hydrolysis, the immobilized naringinase performed over a wide pH application range and had good thermal stability. Even more important, the immobilized naringinase retained 61.81% of the residual naringinase activity after eight consecutive cycles, and kept 80.95% of the residual naringinase activity after one month of storage. This study provides an ideal carrier material and some basic data for naringinase immobilization technology, which will greatly promote the application of naringinase in industrial fruit juice processing.