微生物碳链延长技术转化废弃生物质合成中链脂肪酸

“碳中和”目标下,废弃生物质制备可再生化学品成为落实碳中和、减污降碳等国家重大战略需求的重要技术之一。其中,微生物碳链延长技术生产中链脂肪酸 (MCFAs) 是高值化回收废弃碳源的一个重要方向。MCFAs作为生物基化学品新星,兼具经济、环保与实用性优势,可部分地替代化石原料合成环保型燃料与化学品,降低传统化石资源依赖与碳排放,助力经济社会发展绿色转型。为此,系统梳理了碳链延长技术的反应机理、功能菌群,以及MCFAs生产应用存在的关键瓶颈和研究进展,以期为相关领域研究者开展创新研究、突破技术瓶颈提供参考。     

基于三维荧光光谱特征研究土壤腐殖质氧化还原特性

以国际腐殖质协会腐殖酸和实验室提纯腐殖酸为研究对象,发现被H2还原前后腐殖酸的三维荧光光谱明显不同,但有共同的变化趋势:还原态腐殖酸的三维荧光光谱图的波峰荧光强度均明显低于还原前,说明腐殖酸还原过程有类似π-π*化学键断开的结构变化.对苯醌是腐殖酸氧化还原醌基官能团的代表化合物,将其还原前后与腐殖酸还原前后的荧光光谱对比,发现两组变化趋势一致,这一发现是利用荧光特性量化腐殖质氧化还原官能团的基础.利用铁氰化钾测定腐殖酸的得失电子能力,发现不同土壤提纯的腐殖酸得失电子能力有一定差别:鹰潭土壤腐殖酸和桃源土壤腐殖酸在原态下对三价铁的还原能力都较弱,分别为0.998和0.465 meq.g-1C(原态转移电子数);但还原后得电子数(还原态转移电子数减原态转移电子数)分别为3.384 meq.g-1C(鹰潭土壤腐殖酸)和1.187 meq.g-1C(桃源土壤腐殖酸).鹰潭土壤腐殖酸具有较高的得电子数,与其具有较高荧光峰值这一结果互相支持.结合得失电子能力测定,利用光学分析方法,量化官能团,预测氧化还原反应进程,使三维荧光光谱法测定土壤有机质的氧化还原性在实际应用中具有广阔的前景.     

水稻中硅元素的分布及存在状态

利用UV-Vis分光光度计、X线分析显微镜及扫描电子显微镜(Scanning electron microscope,SEM)对水稻不同器官中硅元素的含量、分布及存在状态进行观察和分析,研究水稻中硅酸的化学性质,为水稻硅元素的综合利用提供科学依据.结果表明:水稻以可溶性原硅酸的形式吸收土壤中的硅酸,同样以可溶性原硅酸的形式输送到各器官中.不同的生长期,水稻导管液内的可溶性原硅酸的含量不同,成熟期最高可达到912 mg/L(以SiO2表示).通过比较导管汁液和土壤溶液的硅酸浓度可知,水稻选择性地吸收和浓缩硅酸,最高浓缩率可达85倍.X线分析显微镜观察发现,硅酸普遍存在于水稻各器官中,越是坚硬的部位硅酸分布得越多.SEM图像表明,沉积在水稻各器官中的硅胶体具有一定的形状且不溶于强酸.对水稻干燥组分中硅酸含量的分析结果表明,稻壳中硅酸含量最高,达到13.3%,是生产硅单质及碳化硅材料的最有效的资源之一.     

碲化镉量子点诱导氧自由基产生的检测

随着量子点(quantum dots,QDs)在生物标记和医学影像等领域的应用日益广泛,其环境暴露量逐渐增加,深入探讨QDs的毒性机制具有重要意义。QDs通过产生活性氧(ROS)诱发毒性效应是目前普遍接受的毒作用模式。为了探讨量子点的毒性与所诱发的ROS的种类和数量的关系,选用碲化镉量子点(CdTe QDs和CdTe/ZnS QDs),利用电子顺磁共振技术(EPR)分别测定了CdTe QDs和CdTe/ZnS QDs在无细胞体系中诱导ROS产生的种类和强度;利用EPR法、紫外可见分光光度法和荧光分光光度法分别测定了4、20和100nmol·mL-1的CdTe QDs和CdTe/ZnS QDs对超氧阴离子(·O2-)和羟基自由基(·OH)产生的促进作用。实验结果显示,CdTe QDs可诱导·O2-的产生;CdTe QDs和CdTe/ZnS QDs对·OH与·O2-的产生有明显的促进作用,且具有剂量-效应关系。研究表明,量子点可诱导和促进ROS产生,不同结构量子点对ROS的诱导和促进作用不同。     

A multi-integrated approach on toxicity effects of engineered TiO2 nanoparticles

The new properties of engineered nanoparticles drive the need for new knowledge on the safety, fate, behavior and biologic effects of these particles on organisms and ecosystems. Titanium dioxide nanoparticles have been used extensively for a wide range of applications, e.g, self-cleaning surface coatings, solar cells, water treatment agents, topical sunscreens. Within this scenario increased environmental exposure can be expected but data on the ecotoxicological evaluation of nanoparticles are still scarce. The main purpose of this work was the evaluation of effects of TiO₂ nanoparticles in several organisms, covering different trophic levels, using a battery of aquatic assays. Using fish as a vertebrate model organism tissue histological and ultrastructural observations and the stress enzyme activity were also studied. TiO₂ nanoparticles (Aeroxide® P25), two phase composition of anatase (65%) and rutile (35%) with an average particle size value of 27.6±11 nm were used. Results on the EC₅₀ for the tested aquatic organisms showed toxicity for the bacteria, the algae and the crustacean, being the algae the most sensitive tested organism. The aquatic plant Lemna minor showed no effect on growth. The fish Carassius auratus showed no effect on a 21 day survival test, though at a biochemical level the cytosolic Glutathione-S-Transferase total activity, in intestines, showed a general significant decrease (p<0.05) after 14 days of exposure for all tested concentrations. The presence of TiO₂ nanoparticles aggregates were observed in the intestine lumen but their internalization by intestine cells could not be confirmed.     

Optimal methods to determine the physical parameters for activated carbon adsorption

The objectives of this research were to examine the physical characteristics of activated carbons made of different materials, thereby suggest a preferable approach to obtaining the optimal estimation of the parameters for the activated carbons by the statistical techniques. After the appropriate pretreatments, the apparent and true densities of activated carbon, adsorption isotherms of argon, nitrogen and mercury, and the adsorptive capacity of benzene were determined by using the recommended approaches. The results showed that the shapes of hysteresis loop indicated that the pores were probably slit‐shaped or formed by plate‐like particles, which could be confirmed by the SEM examination. It was noted that the apparent density used for pore volume calculation presented a higher possibility of underestimation. Through the use of the statistical techniques, such as factor analysis (FA) and correspondence analysis (CA), the principal physical parameters on adsorption phenomena could be characterized. Finally, the optimal methods for obtaining the surface area and pore volume of activated carbons were suggested.     

Toxicity of depleted uranium on isolated liver mitochondria: a revised mechanistic vision for justification of clinical complication of depleted uranium (DU) on liver

Depleted uranium (DU) is widely used in military anti-armor weapons. Recent evidence suggested that oxidative stress and mitochondrial dysfunction may contribute to DU-induced toxicity. However, the underlying mechanisms of DU toxicity in mitochondria are not well understood. In this study, liver mitochondria were obtained from Wistar rats treated with DU in the form of uranyl acetate (UA) (0.5, 1 or 2 mg/kg i.p.) using differential centrifugation. For in vitro experiments, control rat liver mitochondria were incubated with different concentrations of UA (50, 100 or 200 μM) for 1 hr. Mitochondrial reactive oxygen species (ROS) production, collapse of mitochondrial membrane potential, and mitochondrial swelling were examined by flow cytometry. Mitochondrial sources of ROS formation were determined using specific substrates and inhibitors. Extent of lipid peroxidation (LPO) and glutathione (GSH) oxidation, and also complex II and IV activities were detected via spectroscopy. Further, the concentration of ATP and ATP/ADP ratio was measured using luciferase enzyme and release of cytochrome c from mitochondria which was detected by ELISA kit. UA induced succinate-supported mitochondrial ROS production, elevated LPO levels, GSH oxidation, and mitochondrial complex II inhibition. UA also induced mitochondrial permeability transition and increase in cytochrome c release which subsequently disturbed oxidative phosphorylation and reduced the mitochondrial ATP concentration. Data suggest that mitochondrial oxidative stress and uncoupling of oxidative phosphorylation may play key roles in DU-induced hepatic toxicity.     

Adsorption behaviors of activated carbons for the exhaust from spray painting booths in vehicle surface coating

Adsorption performance of activated carbon adsorbers in the downstream duct of vehicle spray painting booths has been studied to understand whether fine paint particles in the off-gas would deteriorate the adsorption capacity of volatile organic compounds (VOCs) on activated carbons. Three forms of activated carbons were selected and their properties were determined using nitrogen adsorption analysis, the measurement of pH value and total ash content, energy dispersion spectrometer, field-emission scanning electron microscopy, and thermogravimetric analysis. Results show that the adsorption capacity of activated carbon strongly depends upon its available specific surface area. When the total uptake on activated carbon approaches saturation, the vapors adsorbed would commence to get displaced by the paint particles gradually as time elapses and finally the uptake of vapors and paint particles reach equilibrium. Microporous carbons, in particular, were much more susceptible to paint particles. A Langmuir-type model for the uptake on activated carbons was suggested, which successfully described the adsorption behaviors of the off-gas released from vehicle spray painting booth.     

亚硫酸盐/紫外体系的还原脱卤效能

水合电子(e-aq)是已知活性最强的还原物种之一.基于SO_3~(2-)受紫外光激发活化会释放e-aq的性质,提出了SO_3~(2-)/UV高级还原体系,用于降解稳定污染物.以7种卤乙酸为目标物,从卤素取代种类、卤代程度、实际水质本底影响等角度,考察了该体系对毒性卤代有机物(HOCs)的降解及脱卤效能,并探讨了相关机理.结果表明:HOCs的降解至少有直接光解和e-aq还原两条途径.卤素取代种类与卤化程度决定了HOCs的直接光解特性,其速率随氯、溴、碘取代顺序及卤化程度的增加而加快.SO_3~(2-)/UV体系显著提高了HOCs的降解及脱卤效率;对于直接光解慢的HOCs,其降解与脱卤主要由e-aq还原引起.SO_3~(2-)/UV体系在两种地表水质本底下仍具有较高的脱卤效能.     

Phase separation and regrowth of aerosol matter collected after size fractionation in an impactor

Aerosol matter in the size range <2 μm was collected in a Berner impactor and subsequently analysed by scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) spectrometry. Owing to the low electron beam energy of 5 keV (occasionally 10 keV), analysis was restricted to elements with atomic numbers 20 (Ca). Sub-micrometer aerosol matter was found to contain mostly S, O, and C as well as some K and Ca. Nitrogen appeared to escape detection, probably due to bombardment-induced sublimation of NO₃ and NH₄. During sampling at low to moderate relative humidity (<60%) the sulphur-rich fraction of the aerosol matter (most likely sulphates) regrew in the form of microcrystals with sizes up to 10 times larger than the mean aerodynamic diameter of the respective impactor stage. By contrast, when sampling during periods in course of which the relative humidity exceeded 70%, the aerosol matter regrew in the form of extended amorphous agglomerates. The aerosol deposits also contained large numbers of carbon nanoparticles, well separated from the regrown sulphate-rich matter. The nanoparticles were similar in size (20–40 nm), much smaller than the equivalent aerodynamic diameter of the impacting particles (63 nm–2 μm). Presumably, the carbon nanoparticles constituted the core of larger air-borne particles covered with sulphates (as well as with nitrates and organic carbon). The regrown microcrystals disappeared rapidly under electron bombardment at high current density, an observation that indicates high volatility at elevated temperatures. Aerosol matter collected in the size range between 1 and 2 μm contained large fractions of particles made of O, Si, P, K, and Ca (oxides). These particles were highly resistant to electron bombardment (hard) and showed little or no evidence for agglomeration or regrowth. After removing the soluble (acidic) material from the collected aerosol matter, only carbon nanoparticles and hard coarse particles were left behind. The observation of agglomerated or crystallized “soft” aerosol matter in combination with phase separation of carbon nanoparticles lends further support to the assertion that it is not possible to collect useful quantities of fine and ultrafine aerosol particles with as-suspended morphology. Some implications for health-related research are discussed.