School of Chemistry and Molecular Engineering, East China University of Science & Technology, Shanghai, 200237, China.
Department of Materials Science and Engineering, University of Delaware, Newark, DE, 19716, USA.
Environ Sci Pollut Res Int. 2019 Sep;26(27):28328-28340. doi: 10.1007/s11356-019-05937-x. Epub 2019 Aug 1.
Chiral mesoporous silica (SiO) with helical structure was synthesized by using anionic surfactants as template. Pre-prepared graphene oxide (GO) was then loaded onto SiO to synthesize composite carrier chial-meso-SiO@GO for the immobilization of laccase. The enzyme activity, thermostability, acid stability, and repeatability of the immobilized enzyme were significantly improved after immobilization. The chial-meso-SiO@GO-immobilized laccase was then used for the degradation of MXC in aqueous phase. The degradation conditions, including temperature, time, pH, MXC concentration, and the dose of immobilized enzyme for cellulosic hydrolysis, were optimized. The optimum conditions for degradation of methoxychlor were selected as pH 4.5, MXC concentration 30 mg/L, immobilized enzyme dose 0.1 g, the maximum MXC removal of over 85% and the maximum degradation rate of 50.75% were achieved after degradation time of six h at temperature of 45 °C. In addition, the immobilized cellulase was added into the immobilized laccase system to form chial-meso-SiO@GO-immobilized compound enzyme with the maximum MXC degradation rate of 59.58%, higher than that of 50.75% by immobilized laccase. An assessment was made for the effect of chial-meso-SiO@GO-immobilized compound enzyme on the degradation of MXC in soil phase. For three contaminated soils with MXC concentration of 25 mg/kg, 50 mg/kg, and 100 mg/kg, the MXC removals were 93.0%, 85.8%, and 65.1%, respectively. According to the GC-MS analyses, it was inferred that chial-meso-SiO@GO-immobilized compound enzyme had a different degradation route with that of chial-meso-SiO@GO-immobilized laccase. The hydrolysis by immobilized cellulase might attack at a weak location of the MXC molecule with its free radical OH and ultimately removed three chlorine atoms from MXC molecule, leading to generating small molecular amount of degradation product.
手性介孔硅（SiO）具有螺旋结构，采用阴离子表面活性剂为模板合成。然后将预先制备的氧化石墨烯（GO）负载到 SiO 上，合成用于固定化漆酶的复合载体手性介孔-SiO@GO。固定化后，固定化酶的酶活性、热稳定性、酸稳定性和重复性均得到显著提高。然后将手性介孔-SiO@GO-固定化漆酶用于水相中甲氧基氯的降解。优化了降解条件，包括温度、时间、pH 值、MXC 浓度和纤维素水解用固定化酶的剂量。选择最适的降解条件为 pH 4.5、MXC 浓度 30 mg/L、固定化酶剂量 0.1 g，在 45°C 下反应 6 h 后，MXC 的最大去除率超过 85%，最大降解率达到 50.75%。此外，将固定化纤维素酶添加到手性介孔-SiO@GO-固定化漆酶体系中，形成最大 MXC 降解率为 59.58%的手性介孔-SiO@GO-固定化复合酶，高于固定化漆酶的 50.75%。评价了手性介孔-SiO@GO-固定化复合酶对土壤相中 MXC 降解的影响。对于 3 种 MXC 浓度分别为 25 mg/kg、50 mg/kg 和 100 mg/kg 的污染土壤，MXC 的去除率分别为 93.0%、85.8%和 65.1%。根据 GC-MS 分析，推断手性介孔-SiO@GO-固定化复合酶的降解途径与手性介孔-SiO@GO-固定化漆酶不同。固定化纤维素酶的水解可能攻击 MXC 分子的薄弱部位，产生游离基 OH，最终从 MXC 分子中去除 3 个氯原子，导致生成少量的降解产物。
