Research progress in microbial cytochrome P450 and xenobiotic metabolism北大核心CSCD

Cytochrome P450 (CYP450s) is a type of heme-mercaptide protein superfamily, which is distributed widely in animals, plants, and microorganisms. CYP450s can oxidize and degrade many exogenous compounds such as drugs, herbicides, pesticides, some persistent organic pollutants, and so on. Based on recent researches, this paper reviews the nomenclature, classification, structure, and catalytic mechanism of P450 enzymes, and summarizes the research progresses in the metabolism and biodegradation of xenobiotics using P450 enzymes from microorganisms. The nomenclature and classification of the P450 gene superfamily mainly rely on the similarities of amino acid sequences. Although the structures of P450 are conserved, their recognition sites towards to the substrates are variable. This is also the structural basis for the catalytic diversities of P450 enzymes. Few P450 enzymes from bacteria and fungi can metabolize and degrade xenobiotics such as polycyclic aromatic hydrocarbons, herbicides, and so on. However, these P450 enzymes are less likely be used in practical applications because of their low catalytic activities. In the future, more P450 enzymes with high degradable efficiencies towards xenobiotics are needed to be obtained using multiple omics tools or modifying the existing P450 enzymes, to achieve the bioremediation of the environment. © 2018 Science Press. All rights reserved.     

Carbon dioxide and methane emission from subsurface peatlands and its controlling factors北大核心CSCD

Peatland is an efficient carbon dioxide (CO2) sink on the continent and plays an important role in global carbon cycle. Climate change and human activities, two of the notable global environmental issues, have accelerated the degradation of peatlands during recent years. Global warming will increase the rate of aerobic decomposition in the surface of peatlands. Carbon stored in the subsurface of peatlands will be metabolized if the climatic conditions become favorable for decomposition. This study reviewed the carbon circle of subsurface peatland in natural environment and in environments disturbed by human activity or climate change. Furthermore, the major factors (environmental and human factors) that affect the carbon cycle were also discussed. According to a previous study, subsurface peatland will rapidly participate in the carbon cycle when the peatland is degraded. Water level, vegetation, and temperature were the main natural factors affecting the carbon cycle, whereas drainage, farming, and grazing were the main anthropogenic factors. Further studies should focus on different soil layer carbon dynamics, inorganic carbon content, and conservation and restoration of peatlands. The study methods should be a combination of macro with micro scale and focus on developing deep peat research techniques. Most of the previous studies focused on greenhouse gas emission and their response factors in short-term experiments. Thus, the mechanism and process of subsurface carbon are not clear and needs further study. © 2018 Science Press. All rights reserved.     

黄孢原毛平革菌处理染料废水过程中细胞结构损伤效应研究

利用透射电子显微镜观察分析白腐真菌(黄孢原毛平革菌)在处理染料废水活性艳红X-3B过程中,染料和盐度对黄孢原毛平革菌的细胞结构产生的毒性作用.结果表明:活性艳红X-3B染料对黄孢原毛平革菌产生生物毒性作用,且随着染料浓度的增加,细胞受损伤程度不断加深.加入100 mg/L的染料活性艳红X-3B后,黄孢原毛平革菌菌丝细胞形态发生变化,出现质壁分离现象;染料浓度进一步加大,菌丝细胞超微结构受到损伤逐渐严重.染料废水中的盐度对黄孢原毛平革菌细胞也会造成损伤,且损伤程度随盐度增大而增大.NaCl浓度为3 g/L时,菌丝细胞发生质壁分离;而当NaCl加入量高于8 g/L时,细胞膜受损,线粒体、细胞核呈现空泡化,表现为受到不可逆的损伤.染料和盐双因子对黄孢原毛平革菌细胞的损伤效应表现为其损伤程度与单因子作用一致,且染料的影响作用占主导.     

Simultaneous compartmentalization of lead and arsenic in co-hyperaccumulator Viola principis H. de Boiss.: an application of SRXRF microprobe

The cellular distributions of Pb and As in the leaves of co-hyperaccumulator Viola principis H. de Boiss. were inspected by synchrotron X-ray fluorescence spectroscopy (SRXRF). The results revealed that Pb and As had similar compartmentalization patterns in the leaves. Both elements were enriched in the bundle sheath and the palisade mesophyll. In comparison with the sheath and the mesophyll, the vascular bundle and the epidermis contained lower levels of Pb and As. The palisade enrichment of Pb and As indicated that V. principis H. de Boiss. may have a special mechanism on detoxification of toxic metals within the mesophyll cells. Relative concentrations of both Pb and As in trichome bases were higher than those in trichome rays. The results of hierarchical cluster analysis and correlation analysis confirmed that the distribution of Pb was similar to that of As in the leaves, and their distribution patterns were different from the nutrient elements, such as K, Ca, Mn, Fe, Ni, Cu and Zn. In vivo cellular localization of Pb and As in the leaves provides insight into the physiological mechanisms of metal tolerance and hyperaccumulation in the hyperaccumulators.     

Effects of rare earth elements on the distribution of mineral elements and heavy metals in horseradish

In order to investigate the effects of rare earth elements (REEs) on horseradish, the distribution of the mineral elements and heavy metals in different organs of horseradish have been studied by using inductively coupled plasma-atomic emission spectrometry (ICP-AES). Meanwhile, three variable major parameters, namely the concentration of REEs, the type of REEs, and the growth stage of plant were chosen. The results indicated that the test REEs, Ce(III) and Tb(III), could be accumulated in leaves, stems and roots of horseradish. In addition, we found that the content of mineral elements was increased in horseradish treated with 20mgl(-1) of Ce(III), but not those with the 20mgl(-1) of Tb(III). Moreover, the content of mineral elements in horseradish was decreased with the increasing concentration of REEs (100, 300mgl(-1)). Furthermore, we found that there were the opposite effects on the content of the heavy metals in horseradish treated with REEs. Finally, we found that the effect of REEs on the accumulation of REEs, and the content of mineral elements or heavy metals of horseradish during vigorous growth stage, no matter positive or negative, was more obvious than that of the other growth stages. These results demonstrated that the distribution behaviors of mineral elements and heavy metals in horseradish can be affected by the type and concentration of REEs, and the growth period of plant.     

PAC-chitosan复合絮凝剂中铝形态

以不同碱化度(B)的聚合氯化铝(PAC)和不同粘度的壳聚糖为原料制备出一系列PAC-chitosan复合絮凝剂。采用Al-Ferron逐时络合比色法研究了PAC-chitosan复合絮凝剂中铝的形态分布,探讨了PAC的B值、壳聚糖的含量（C）和粘度（η）对复合絮凝剂中铝的形态分布的影响。结果表明：壳聚糖与PAC之间发生了一定的相互作用,通过试验结果推断出当B=1.5,壳聚糖粘度η=800 Pa·s,C=0.6 mg/mL絮凝效果最佳。并用某造纸废水进行了烧杯絮凝试验。絮凝试验结果与推断结果相一致。     

Health risks of heavy metals in contaminated soils and food crops irrigated with wastewater in Beijing, China

Consumption of food crops contaminated with heavy metals is a major food chain route for human exposure. We studied the health risks of heavy metals in contaminated food crops irrigated with wastewater. Results indicate that there is a substantial buildup of heavy metals in wastewater-irrigated soils, collected from Beijing, China. Heavy metal concentrations in plants grown in wastewater-irrigated soils were significantly higher (P相似文献   

Different reaction mechanisms of diphenylether and 4-bromodiphenylether with nitrous acid in the 355 nm laser flash photolysis of mixed aqueous solution

The microscopic reaction mechanisms of diphenylether (DPE) and 4-bromodiphenylether (4-BrDPE) with nitrous acid (HNO(2)) in the absence of O(2) have been explored by the 355nm laser flash photolysis. It was proposed that OH radical, from the photolysis of HNO(2), added to DPE forms the C(12)H(10)O-OH adduct while added to 4-BrDPE forms the 4-BrDPE-OH and 4-BrOH-DPE adducts. The first-order decay rate constants of the C(12)H(10)O-OH adduct, 4-BrDPE-OH adduct and 4-BrOH-DPE adduct were measured to be (1.86+/-0.14)x10(5)s(-1), (2.19+/-0.04)x10(5)s(-1) and (1.56+/-0.03)x10(5)s(-1), respectively. The final photolysis products of DPE and HNO(2) identified by GC/MS analysis were phenol, o-hydroxydiphenylether, p-hydroxydiphenylether and p-nitrodiphenylether, while the final photolysis product of 4-BrDPE and HNO(2) identified by LC/MS analysis was mainly the dimer.     

Occurrence of phthalates in sediment and biota: relationship to aquatic factors and the biota-sediment accumulation factor

Phthalate compounds in sediments and fishes were investigated in 17 Taiwan's rivers to determine the relationships between phthalate levels in sediment and aquatic factors, and biota-sediment accumulation factor (BSAF) for phthalates. Mean concentrations (range) of di(2-ethylhexyl) phthalate (DEHP), butyl benzyl phthalate (BBzP) and di-n-butyl phthalate (DBP) in sediment at low-flow season were 4.1 (<0.05-46.5), 0.22 (<0.05-3.1) and 0.14 (<0.05-1.3)mgkg(-1)dw; those at high-flow season were 1.2 (<0.05-13.1), 0.13 (<0.05-0.27) and 0.09 (<0.05-0.22)mgkg(-1)dw, respectively. Trace levels of dimethyl phthalate (DMP), diethyl phthalate (DEP) and di-n-octyl phthalate (DOP) in sediment were found in both seasons. Concentrations of DEHP in sediments were significantly affected by temperature, suspended solids, ammonia-nitrogen, and chemical oxygen demand. The highest concentration of DEHP in fish samples were found in Liza subviridis (253.9mgkg(-1)dw) and Oreochromis miloticus niloticus (129.5mgkg(-1)dw). BSAF of DEHP in L. subviridis (13.8-40.9) and O. miloticus niloticus (2.4-28.5) were higher than those in other fish species, indicating that the living habits of fish and physical-chemical properties of phthalates, like logKow, may influence the bioavailability of phthalates in fish. Our data suggested that DEHP level in river sediments were influenced by water quality parameters due to their effects on the biodegradation processes, and that the DEHP level in fish was affected by fish habitat and physiochemical properties of polluted contaminants.     

CO2捕集回收技术研究

主要介绍了常用的胺化合物吸收法、钙基吸收剂法、金属氧化物法等CO2捕集回收技术的最新研究进展及存在的问题,综合对比了各种方法的优缺点:胺化合物吸收法吸收速率快,但再生能耗较高,因此开发"高效低耗"的复合吸收剂成为研究的重点;钙基吸收剂法在高温环境下对CO2的吸收有较好的效果,但吸收剂的碳酸化转化率及热稳定性是有待解决的关键问题;金属氧化物法具有高的CO2吸收效率,但成本较高.在此基础上,探索了CO2捕集回收技术改进工艺,提出改善吸收剂性能、开发高效低耗的CO2选择性吸收剂将成为今后CO2捕集回收技术的研究方向.