Immobilization of the crude enzyme extracted from Stenotrophomonas sp. GYH within modified zeolitic imidazolate framework (ZIF-8-NH2) and its application in trichloromethane removal
Zhuowei Cheng, Zhirong Sun, Wei Fang, Jianming Yu, Jingkai Zhao, Jianmeng Chen, Jiade Wang, Yongcai Zhang
Abstract
Enzyme immobilization, due to its higher effective density in a limited micro space, can effectively improve the removal efficiency for some recalcitrant compounds. Metal–organic frameworks (MOFs) have been identified as having attractive properties for the immobilization of enzymes, such as high surface area, large internal pore volumes and easily adjustable pore size. In the present study, a new immobilization carrier was synthesized through the modification of zeolitic imidazole framework-8 (ZIF-8) by 2-aminobenzimidazole, which was employed for enzymes immobilization for the first time. The immobilized bio-enzyme was extracted from trichloromethane (TCM) degrader Stenotrophomonas sp. GYH, and identified through label-free quantitative proteomics. Based on the metabolites detection and molecular docking, a proper degradation pathway for TCM was proposed, in which some key enzymes were tagged with the specific role. XRD, BET, and FTIR analyses proved that ZIF-8-NH2 was proper as the immobilization carrier. The [email protected]2 prepared under the best immobilized conditions had a similar relative enzyme activity to that of free enzyme (the Michaelis kinetic constant Km was 3.86 and 3.78 min−1), but it had better pH and temperature adaptability (pH 5−9 and temperature 10−50 °C), better storage stability (83% and 40% of the initial enzyme activity at 30 d) and so on. The density functional theory (DFT) results show that the ZIF-8-NH2 carrier has a better TCM and CO2 adsorption energy, which is consistent with the fact that the [email protected]2 had better TCM degradation efficiency and less CO2 emission to the surroundings.