| The preparation and application of catalase powder immobilized by chitosan used as a kind of cigarette filter additive was investigated in the present paper. The results showed that:1. Catalase was immobilized on chitosan with glyoxal by cross-linking reaction. The conditions for immobilization were optimized as follows: 3% chitosan 20ml, cross-linking reagent 100ml, enzyme 6ml, the concentration of glyoxal 6%, adsorption time 2.5h, cross-linking reaction time 0.5h. The activity yield of the immobilized catalase was 42.9% of the original.2. The characteristics of the immobilized catalase such as the optimal pH, thermal stability, and storage stability were assessed. The Km, an important kinetic parameter of enzyme, was obtained as 61.7 mmol/L with Lineweaver-bulk method. Immobilized catalase has the same optimum pH (7.0) as the free enzyme, and the pH profile of it was broader with respect to the free enzyme.3. The study showed that the activity catalase can scavenge free radical in Water-UV-TiO2 system, while the catalase denaturalized by heat nearly can't, which means that only activity catalase can scavenge free radicals.4. Moreover, the immobilized catalase was found to be able to remove superoxide anion free radical (SAFR) produced in pyrogallic acid system.5. It was found that immobilized catalse added in cigarette filter cleared away free radicals in mainstream smoke. The free radicals in gas phase were decreased 6.5%, 9.9% and 15.1%, and that in tar decreased 2.3%, 21.9% and 40.8% as the quantity of immobilized catalase appended was 10, 30 and 50mg/cig. The results showed that free radicals in mainstream smoke were reduced significantly with the increase of immobilized catalase added.6. It was observed that immobilized catalse added in cigarette filter can reduce other toxicants in mainstream smoke. TPM, tar, nicotine and TSNA, was reduced 60%, 50%, 28% and 25%, respectively.
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