Immobilization Of Magnetically Responsive GOD And Its Bleaching Of Cotton Fibers

Glucose oxidase can be widely used in textile,food,biosensor and other fields.However,the free glucose oxidase is easy to be inactivated,difficult to recovery and so on,which lead to high cost of glucose oxidase.Therefore,the application of free glucose oxidase in indurstrial field is limited.Enzyme immobilization can improve the stability of the enzyme,achieve recovery and reuse,reduce costs,conducive to the large-scale production and utilization of enzymes.The magnetic immobilized glucose oxidase was prepared by static attraction between the enzyme and the carrier.The magnetic immobilized glucose oxidase was prepared by using PDDA-coated Fe₃O₄ magnetic particles as carrier.And then the immobilized glucose oxidase is expected to rapidly recovery by magnetism.The immobilization parameters were studied to analyze the properties of immobilized enzyme.The immobilized glucose oxidase was used to decompose the glucose,and the produced hydrogen peroxide was used to bleach the cotton fabric.The main contents and results are as followed.1)Fe₃O₄ nanoparticles were prepared by coprecipitation method with NaOH and ammonia as precipitant respectively in air atmosphere.Fe₃O₄ was coated with strong cationic polyelectrolyte PDDA.The morphologies and magnetic properties of Fe₃O₄ were analyzed by scanning electron microscopy,X-ray diffraction and vibrating magnetometer.The results show that under the same conditions,near-superparamagnetism of about 10 nm is prepared by using ammonia as precipitant.Fe₃O₄ nanoparticles have a specific saturation magnetization of 73.114 emu/g and the performance is better than that of NaOH as precipitant.When the concentration of PDDA was 20%,the ultrasonic time was 30min and the coating temperature was 20℃,the particle size of PDDA-Fe₃O₄ composite nanoparticles was less than 20nm,the’saturation magnetization was 58.583emu/g,the coercivity was 9.2558 Oe,close to superparamagnetism.2)Immobilization of glucose oxidase was carried out with PDDA-Fe₃O₄ nanoparticles as carrier.The optimum conditions of immobilized enzyme were immobilization temperature of 5℃,buffer solution of pH 7,carrier weight of 1.5g,The amount of 5 mg.The mass ratio of enzyme to carrier was 1:30.The optimal pH of the immobilized enzyme was 8 and the optimal reaction temperature was 60℃.The activity of immobilized glucose oxidase was maintained at 68%after five times of continuous catalysis.The thermal stability and pH stability of immobilized glucose oxidase has been increased in comparison with that of the free enzyme.3)The influence factors（reaction time,hydrogen peroxide concentration,reaction temperature and pH）of cotton fabric bleaching were optimized by Design-Expert software.The mathematical model was established and validated.The results showed that the correlation between the predicted value and the true value was 96.8%,and the maximum value of the whiteness of the cotton fabric was obtained.The reaction time was 85.23min,the concentration of hydrogen peroxide in the bleaching solution was 4.22g/L,the temperature was 96.95℃,the pH value was 10.86.With such reaction conditions,the predicted whiteness value was 89.3883.Considering the actual experimental conditions,the experimental conditions were modified as followed.The reaction time was 85min,the concentration of hydrogen peroxide in the bleaching solution was 4.3g/L,the temperature was 97℃ and the pH was 10.8.The results show that the optimized bleaching process of cotton fabric by hydrogen peroxide is reasonable.The results show that the whiteness of the bleached cotton fabric is reasonable and the whiteness is 89.22,which is less than 2%from the whiteness prediction.The pH value of the bleaching solution has a significant effect on the mechanical properties of the fabric.The higher the pH value is,the worse the mechanical properties of the fabric is.