Study On Silica-based Biocatalysts

Enzyme is a special catalyst with high efficiency, specificity and adjustableactivity. However, it is susceptive to its environment surrounded. Acidic or alkalineconditions, high temperature and ionic strength change may cause catalytic activitydecrease or completely lose. In order to overcome these problems, immobilizedenzyme technology was invented. Choosing a suitable immobilized method for eachenzyme is the important for immobilized enzyme technology.Blood is a waste product of the slaughter industry, while its main componenthemoglobin （Hb） is a pseudo-peroxidase which is able to oxidize polycyclicaromatic hydrocarbons （PAHs） in the presence of H2O2. In order to use Hb forwastewater treatment, we encapsulated it in silica-based matrix by modified“fish-in-net” approach. The as-synthesized catalysts were named MSF-Hb andcharacterized by SEM, TEM, BET and solid-state UV–vis spectroscopy. It wasfound that Hb was partially homogeneously dispersed in microspheres and showedmore stable peroxidase-like activity than free Hb. Moreover, it had substantiallyincreased storage stability as well as pH stability. It was used as biocatalyst toremove PAHs in aqueous solution and gave a satisfactory reduction of removal. Nosignificant activity loss was observed after ten runs. These experimental resultssuggest that the resultant product was a promising biocatalyst for aromaticwastewater treatment.In recent years, magnetic functional composites have attracted a lot ofattentions for the rapid magnetic separation. They have many applications inbiological and some other fields. In order to use the magnetic properties andfacilitate the separated process, Fe₃O₄microspheres have been encapsulated withmesoporous silica as well as hemoglobin. The results revealed that the material holda core/shell structure and showed typical ordered mesoporous characteristics,magnetic feature and peroxidase activity. Interestingly, the structure and synthesisprocess of Fe₃O₄@mSiO₂（Hb） was similar with a traditional Chinese food---yuanxiao. The product Fe₃O₄@mSiO₂（Hb） was used to remove PAHs fromwastewater, which showed satisfactory reusability and removal efficiency.Both myoglobin and another Fe3O4nanoparticles （diameter:15²0nm） wereencapsulated with mesoporous silica materials. The as-obtained products werecharacterized by XRD, SEM, TEM, solid-state UV and N2adsorption/desorption.The results showed that the structure of the product was like a “pitaya”. It revealedsatisfactory activity, magnetic properties and reusability. Different kinds ofstabilities （including pH, temperature and storage stability） were investigated andthey were all improved. It`s deduced that the silica carrier acts as a protective layerfor the enzyme and enhanced its tolerance towards environmental changes.