Cell surface-expression of the phosphate-binding protein PstS: System development, characterization, and evaluation for phosphorus removal and recovery

Simultaneous overabundance and scarcity of inorganic phosphate(P_i) is a critical issue driving the development of innovative water/wastewater treatment technologies that not only facilitate Pi removal to prevent eutrophication,but also recover P_i for agricultural reuse.Here,a cell-surface expressed high-affinity phosphate binding protein(PstS) system was developed,and its P_i capture and release potential was evaluated.E.coli was genetically modified to express PstS on its outer membrane using the ice nucleation protein(INP)as an anchoring motif.Verification of protein expression and localization were performed utilizing SDS-polyacrylamide gel electrophoresis(SDS-PAGE),western blot,and outer membrane separation analyses.Cell surface characterization was investigated through acid-base titration,X-ray photoelectron spectroscopy(XPS),and Fourier transform infrared spectroscopy(FTIR).These tests provided information on the macromolecular structure and composition of the bacteria surface as well as the proton-exchange properties of the surface functional groups(i.e.,pKa values).Phosphate desorption and adsorption batch experiments were conducted to evaluate the effects of temperature,pH,and ionic strength on phosphate capture and release.The PstS surface-displayed cells demonstrated greater potential to release and capture phosphate compared to non-modified cells.Higher temperatures up to 40℃,basic pH conditions(pH=10.5),and higher ionic strength up to 1.0 mol/L KCl promoted 20%-50% higher phosphate release.     

Influence of plant activity and phosphates on thorium bioavailability in soils from Baotou area, Inner Mongolia

Harm of thorium to living organisms is governed by its bioavailability. Thorium bioavailability in the soil-plant system of Baotou rare earth industrial area was studied using pot experiments of wheat and single extraction methods. The effects of wheat growth stage and phosphate on thorium bioavailability were also investigated. Based on extractabilities of various extraction methods (CaCl₂, NH₄NO₃, EDTA, HOAc) and correlation analysis of thorium uptake by wheat plant and extractable thorium, a mixture of 0.02 M EDTA + 0.5 M NH₄OAc (pH 4.6) was found suitable for evaluation of thorium bioavailability in Baotou soil, which could be predicted quantitatively by multiple regression models. Because of differences of wheat root activities, thorium bioavailability in rhizosphere soil was higher than in bulk soil at tillering stage, but the reverse occurred at jointing stage. Phosphate addition induced the mineralization of soluble thorium by forming stable thorium phosphate compounds, and reduced thorium bioavailability in soil.     

Phosphate rock formation and marine phosphorus geochemistry: the deep time perspective

The role that phosphorite formation, the ultimate source rock for fertilizer phosphate reserves, plays in the marine phosphorus (P) cycle has long been debated. A shift has occurred from early models that evoked strikingly different oceanic P cycling during times of widespread phosphorite deposition to current thinking that phosphorite deposits may be lucky survivors of a series of inter-related tectonic, geochemical, sedimentological, and oceanic conditions. This paradigm shift has been facilitated by an awareness of the widespread nature of phosphogenesis—the formation of authigenic P-bearing minerals in marine sediments that contributes to phosphorite formation. This process occurs not just in continental margin sediments, but in deep sea oozes as well, and helps to clarify the driving forces behind phosphorite formation and links to marine P geochemistry.Two processes come into play to make phosphorite deposits: chemical dynamism and physical dynamism. Chemical dynamism involves the diagenetic release and subsequent concentration of P-bearing minerals particularly in horizons, controlled by a number of sedimentological and biogeochemical factors. Physical dynamism involves the reworking and sedimentary capping of P-rich sediments, which can either concentrate the relatively heavy and insoluble disseminated P-bearing minerals or provide an episodic change in sedimentology to concentrate chemically mobilized P. Both processes can result from along-margin current dynamics and/or sea level variations. Interestingly, net P accumulation rates are highest (i.e., the P removal pump is most efficient) when phosphorites are not forming. Both physical and chemical pathways involve processes not dominant in deep sea environments and in fact not often coincide in space and time even on continental margins, contributing to the rarity of high-quality phosphorite deposits and the limitation of phosphate rock reserves. This limitation is becoming critical, as the human demand for P far outstrips the geologic replacement for P and few prospects exist for new discoveries of phosphate rock.     

Factors affecting the degradation of amoxicillin in composting toilet

The biological and non-biological factors that affect the degradation of amoxicillin in the composting process of feces have been investigated. The effect of living bacteria and the enzyme (beta-lactamase) on amoxicillin decay was examined, and our results indicated that the biological effects are likely to be negligible. Consequently, the effect of phosphate, ammonia and pH level as non-biological factors was investigated by monitoring the reduction rate of amoxicillin in phosphate and ammonia buffer solutions with several pH levels. Each reduction rate constant was integrated by a simulation model, and the each calculated amoxicillin reduction profile was compared to the reduction profiles of amoxicillin in the composting process of feces. The calculated results corresponded almost exactly to the experimental profiles. We therefore concluded that the degradation of amoxicillin in a toilet matrix was dependent on the concentration of ammonia, phosphate and hydroxyl ion.     

Synthesis of porous iron hydroxy phosphate from phosphate residue and its application as a Fenton-like catalyst for dye degradation

Phosphate residue is a kind of hazardous solid waste and if not properly disposed of, could cause serious environmental contaminations. The abundant iron salt available in phosphate residue can be used to prepare photo-Fenton catalytic reagent for wastewater treatment. In this study, the phosphate residue was effectively purified by a hydrothermal recrystallization method, reaching an iron phosphate purity of 94.2%. The particles of iron phosphate were further processed with ball milling with th...     

氢氧化铌对水溶液中磷酸根的吸附特性研究

以氢氟酸法制备的氢氧化铌作为磷酸根的吸附剂,考察了氢氧化铌用量及焙烧温度对吸附效果的影响。在25℃,磷酸根初始浓度为50mg/L、体积200mL的条件下,确定吸附剂的最佳用量为0.1g,此时氢氧化铌原样对磷酸根的最大吸附量为48.2mg/g。上述条件下,经200、300、400、500℃焙烧后的氢氧化铌对磷酸根的最大吸附量依次为25.9、15.6、11.6、7.5mg/g。分析表明,随着焙烧温度的升高,表面羟基逐渐减少,氢氧化铌对磷酸根的吸附能力逐渐降低。在吸附过程中,焙烧前后的氢氧化铌对磷酸根吸附速率均较快(20min达到吸附平衡)。     

含DOPO磷酸酯阻燃改性环氧丙烯酸树脂的制备及热性能研究

将工业上广泛应用的光固化树脂EA作为基体,通过分子设计,利用甲苯二异氰酸酯TDI的双异氰酸酯结构将合成的磷酸酯阻燃剂ODOPM链接到其分子主链上,制备出一组改性的光固化丙烯酸酯预聚物。利用FT-IR,1 H-NMR,31P-NMR对分子结构进行表征;极限氧指数（LOI）和微型量热仪（MCC）的结果表明材料的阻燃性能明显提高,改性后树脂的热释放速率峰值PHRR相对于EA降低了近66%,总热释放量也明显降低;扫描电镜结果显示改性后的树脂固化膜形成的炭层变得更平滑和致密,并且完整无破裂现象;同时对固化膜的热稳定性和热降解过程进行了探讨。分析论证了ODOPM改性修饰后的EA有更高的阻燃性,成炭能力明显增强,形成的致密炭层有效地阻止了热交换,使材料在高温下更稳定。     

城市污水化学除磷的探讨

阐述了城市污水处理除磷的重要性和迫切性，而在普遍采用的生物除磷技术不能满足出水磷的排放标准时可考虑采用化学除磷技术，系统分析了化学除磷的原理，特点及影响因素，结合工程实例介绍了城市污水化学除磷的除磷效果，并指出了我国在现阶段城市的污水化学除磷技术研究与发展的目标。     

Wastewater remediation using coal ash

 Small-scale domestic septic tanks discharge excess nutrients such as phosphorus and nitrogen, as well as pathogens, which can degrade local water supplies. Unfortunately, traditional chemical and physical treatments are not practicable for single-home dwellings. This work reports on a potentially attractive solution to protect local water supplies by using a low-cost industrial waste, coal ash, for contaminant removal. Coal ash is produced as a consequence of electric power generation. The majority of the ash is disposed of in landfills and surface impoundments, or stored on- or off-site, producing large hills or leveling valleys. Only a small portion of the ash is ever utilized, mainly by cement industries and road construction. For example, in Canada less than 25% is used. Therefore, if useful applications can be found, an opportunity exists to make better use of this waste material. Bench-scale laboratory experiments and full-scale field tests show that coal ash has the capacity to remove phosphorus from domestic waste water. The experimental and field data demonstrate that phosphate levels and calcium levels can be correlated, although not in a simple manner. In addition, the ash in packed beds removed total suspended solid (TSS), biological oxygen demand (BOD), ammonia nitrogen (NH₃—N), total Kjeldahl nitrogen (TKN), and E. coli. The removal of E. coli was close 100% in the cases studied. Received: May 20, 2002 / Accepted: October 5, 2002     

反相流动注射法测定海水中磷酸盐

建立了反相流动注射-结晶紫-磷钼杂多酸离子缔合体系测定海水中磷酸盐的方法,确立了最佳试验条件,有效解决了海水的盐度干扰问题.方法线性良好,检出限为0.1 μg/L,精密度和准确度均符合要求,且流路简单,操作方便,可用于现场自动分析.