| Naringinase has important application value in debittering of citrus fruit juice.Citrus pomace waste is rich in bioactive ingredients,dietary fiber,vitamins and trace elements,which can be used in the fermentation process of naringinase.In this paper,citrus pomace extract was used as the medium component,and the consist of culture medium for naringinase production via Aspergillus niger was optimized.Magnetic silica material was used for in-situ separation/immobilization of naringinase,and the immobilization process and enzyme properties was studied.The main results are as follows:When the ratio of fruit residue to water was 1:8,5.5 g/L of bran powder was used as carbon source,and the ratio of ammonium sulfate to yeast extract powder was 7:3 as nitrogen source,the naringinase activity reached 1180.15 U/m L,which was 15.3 times of that under the condition of no optimization.Magnetic nanoparticles Fe3O4@SiO2-NH2 were prepared and modified with glutaraldehyde at 5%for 4 h at 45?.The results showed that at pH 4.0,the initial amount of naringinase was 134.44 U/m L,the immobilization temperature was 35?,and the immobilization time was 4 h,the specific activity of the immobilized naringinase reached330.53 U/g.The optimum reaction conditions of immobilized naringinase was pH 5.0 and reaction temperature of 60?.The naringin enzyme immobilization of fixed rate,enzyme activity and the recovery of energy were 68.74%,63.89%and 376.59 U/g,respectively.Meanwhile,comparing with free enzyme,in-situ immobilized naringinase exhibited better pH stability and temperature stability.After 10 cycles of continuous use,there was still51.5%of naringinase activity remained,indicating that the immobilized naringinase had good reusability.Furthermore,the kinetic and thermodynamic processes of free naringinase and in situ immobilized naringinase were caculated and analyzed.The results showed that the catalytic efficiency and thermal stability of immobilized naringinase were obviously improved. |
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