Characterization and application of a recombinant dopa decarboxylase from Harmonia axyridis for the efficient biosynthesis of dopamine

Here,a dopa decarboxylase (DDC) from Harmonia axyridis was heterogeneously expressed in Escherichia coli for the efficient biosynthesis of dopamine.For the production of recombinant DDC,the cultivation conditions including IPTG concentration,temperature and induction time were optimized and obtained an optimal specific enzyme activity of 51.72 U·mg-1 crude extracts.After the purification of DDC with a recovery yield of 68.79％,its activity was further characterized.The Vmax,Km,Kcat,and Kcat/Km of DDC for dihydroxyphenylalanine (dopa) were 0.02 mmol·ml-1·s-1,2.328 mmol·ml-1,10435.90 s-1 and 4482.77 ml·mmol-1·s-1,respectively.The highest DDC activity was observed at the condition of pH 7.5 and 45 ℃.With the purified DDC,the feasibility to produce dopamine from L-dopa was evaluated.The optimal yield was determined at the following bioconversion conditions:pH of 7.0,the reaction temper-ature of 40 ℃,0.4 mmol·L-1 of PLP and 4 g·L-1 of L-dopa.Subsequently,a fed-batch process for the pro-duction of dopamine was developed and the effect of oxygen was evaluated.The titer,yield and productivity of dopamine reached up to 21.99 g·L-1,80.88％ and 14.66 g·L-1h-1 at 90 min under anaer-obic condition.     

Degradation and mineralization of aniline by O3/Fenton process enhanced using high-gravity technology

The degradation and mineralization of aniline(AN) using ozone combined with Fenton reagent(O_3/Fenton) in a rotating packed bed(RPB) was proposed in this study, and the process(RPB-O_3/Fenton) was compared with conventional O_3/Fenton in a stirred tank reactor(STR-O_3/Fenton) or single ozonation in an RPB(RPB-O_3). Effects of high gravity factor, H_2O_2 dosage, H_2O_2 dosing method and initial p H on the AN mineralization efficiency were investigated in the RPB-O_3/Fenton process. In addition, the behavior of Fe(II) was monitored at different H2 O2 dosing methods and p H values. Finally, the optimal operation conditions were determined with high gravity factor of100, initial pH of 5, Fe(II) concentration of 0.8 mmol·L~(-1) and H_2O_2 dosage of 2.5 ml. Under these conditions, for aniline wastewater at the volume of 1 L and concentration of 200 mg·L~(-1), a fast and thorough decay of AN was conducted in 10 min, and the TOC removal efficiency reached 89% in 60 min. The main intermediates of p-benzoquinone, nitrobenzene, maleic acid and oxalic acid were identified by liquid chromatography/mass spectroscopy(LC/MS), and the degradation pathways of AN in RPB-O_3/Fenton system were proposed based on experimental evidence. It could be envisioned that high-gravity technology combined with O_3/Fenton processes would be promising in the rapid and efficient mineralization of wastewater.     

TiO2光催化降解2,4-二氯酚动力学及机理的研究

以TiO2作为催化剂,500 W汞灯作为光源,对水体中2,4-二氯酚（2,4-DCP）的光催化降解特性进行了研究。实验结果表明,TiO2光催化降解2,4-DCP效果较好,降解的最佳pH为7,催化剂的最佳投加量为200 mg·L-1。2,4-DCP的初始浓度越小,光催化的效率越高。在初始浓度为5 mg·L-1时,光催化1 h的降解率达90%。在实验的四种不同初始浓度（5 mg·L-1、10 mg·L-1、20 mg·L-1、40 mg·L-1）下,2,4-DCP的光降解速率常数近似与其初始质量浓度成一级反应动力学关系。结合高效液相色谱、气相色谱-质谱的测定结果以及Cl-、COD的变化,认为2,4-DCP的主要降解过程为：脱氯-开环-矿化、中间产物相互作用-进一步矿化。     

正磷酸活化木质素吸附Cr(Ⅵ)的固定床实验和模型(英文)

The advantage of using an available and abundant residual biomass,such as lignin,as a raw material for activated carbons is that it provides additional economical interest to the technical studies.In the current investigation,a more complete understanding of adsorption of Cr(VI) from aqueous systems onto H3PO4-acid activated lignin has been achieved via microcolumns,which were operated under various process conditions.The practice of using microcolumn is appropriate for defining the adsorption parameters and for screening a large number of potential adsorbents.The effects of solution pH(2-8),initial metal ion concentration(0.483-1.981 mmol·L-1),flow rate(1.0-3.1 cm3·min-1),ionic strength(0.01-0.30 mmol·L-1) and adsorbent mass(0.11-0.465 g) on Cr(VI) adsorption were studied by assessing the microcolumn breakthrough curve.The microcolumn data were fitted by the Thomas model,the modified Dose model and the BDST model.As expected,the adsorption capacity increased with initial Cr(VI) concentration.High linear flow rates,pH values and ionic strength led to early breakthrough of Cr(VI).The model constants obtained in this study can be used for the design of pilot scale adsorption process.     

Synthesis of activated carbon from spent tea leaves for aspirin removal

Adsorption capacity of activated carbon prepared from spent tea leaves(STL-AC) for the removal of aspirin from aqueous solution was investigated in this study. Preliminary studies have shown that treatment with phosphoric acid(H_3PO_4) increased removal efficiency of STL-AC. Characterizations on STL-AC revealed excellent textural properties(1200 m~2·g~(-1), 51% mesoporosity), as well as distinctive surface chemistry(1.08 mmol·g~(-1) and 0.54 mmol·g~(-1) for acidic and basic oxygenated groups, pH_(pzc)= 2.02). Maximum removal efficiency of aspirin observed was 94.28% after 60 min when the initial concentration was 100 mg·L~(-1), 0.5 g of adsorbent used,pH 3 and at a temperature of 30 ℃. The adsorption data were well fitted to the Freundlich isotherm model and obeyed the pseudo-second order kinetics model. The adsorption of aspirin onto STL-AC was exothermic in nature(ΔH~Θ=~(-1)3.808 k J·mol~(-1)) and had a negative entropy change, ΔS~Θ(-41.444 J·mol~(-1)). A negative Gibbs free energy, ΔG~Θ was obtained indicating feasibility and spontaneity of the adsorption process. The adsorption capacity of AC-STL(178.57 mg·g~(-1)) is considerably high compared to most adsorbents synthesized from various sources, due to the well-defined textural properties coupled with surface chemistry of STL-AC which favors aspirin adsorption. The results demonstrate the potential of STL-AC as aspirin adsorbent.     

Complete mineralization of the antibiotic amoxicillin by electro-Fenton with a BDD anode

On April 30, 2014, the World Health Organization’s first global report on the presence of antibiotics in waters focused on their negative consequences, which may include the growth of microorganisms with antimicrobial resistance. The β-lactam antibiotic amoxicillin (AMX) is widely used in human and veterinary medicine, and it has been recently detected in sewage treatment plants and effluents. In this paper, the degradation of acidic aqueous solutions of AMX by electro-Fenton process has been studied at constant current. Experiments have been performed in an undivided cell equipped with a carbon-felt cathode and a Pt or boron-doped diamond (BDD) anode. In such systems, the organic molecules are mainly oxidized by hydroxyl radical (^?OH) simultaneously formed on the anode surface from water oxidation as well as in the bulk from Fenton’s reaction between Fe²⁺ catalyst and electrogenerated H₂O₂. The decay and mineralization of AMX was monitored by means of high performance liquid chromatography (HPLC) and TOC measurements. The evolution of the concentration of the final aliphatic carboxylic acids and inorganic ions like ammonium, nitrate and sulfate was assessed by HPLC and ion chromatography, respectively. The effect of the anode material, initial AMX concentration and current density was thoroughly studied. The AMX decay always followed a pseudo-first-order kinetics using either Pt or BDD, and the apparent rate constant increased with applied current. A quicker mineralization was reached with BDD because of the larger production of active ^?OH. The absolute rate constant between hydroxyl radical and AMX determined by the competition kinetics method using p-hydroxybenzoic acid as the reference compound was found to be (2.02 ± 0.01) × 10⁹ M^?1 s^?1.     

Novel kinetic model for the simulation analysis of the butanol productivity of Clostridium acetobutylicum ATCC 824 under different reactor configurations

Acetone–butanol–ethanol(ABE)fermentation process can be exploited for the generation of butanol as biofuel,however it does need to overcome its low volumetric solvent productivity before it can commercially compete with fossil fuel technologies.In this regard,mathematical modelling and simulation analysis are tools that can serve as the base for process engineering development of biological systems.In this work,a novel phenomenological kinetic model of Clostridium acetobutylicum ATCC 824 was considered as a benchmark system to evaluate the behaviour of an ABE fermentation under different process configurations using both free and immobilized cells:single stage batch operation,fed-batch,single stage Continuous Stirred Tank Reactor(CSTR)and multistage CSTRs with and without biomass recirculation.The proposed model achieved a linear correlation index r~2=0.9952 and r~2=0.9710 over experimental data for free and immobilized cells respectively.The predicted maximum butanol concentration and productivity obtained were 13.08 g·L~(-1)and 1.9620 g·L~(-1)·h~(-1)respectively,which represents an increase of 1.01%and 990%versus the currently developed industrial scale process reported currently into the literature.These results provide a reliable platform for the design and optimization of the ABE fermentation system and showcase the adequate predictive nature of the proposed model.     

Experimental design methodology applied to electro-Fenton treatment for degradation of herbicide chlortoluron

The degradation of herbicide chlortoluron in aqueous medium by electro-Fenton process using a carbon felt cathode and a platinum anode was studied. The great oxidation ability of this process is due to the large production of hydroxyl radical (OH) by electrochemically induced Fenton's reagent. Hydroxyl radicals are very powerful oxidizing agents which react on organics up to complete mineralization. The influence of some experimental parameters such as initial concentration, current intensity and processing time on the degradation and mineralization rate of chlortoluron by hydroxyl radicals has been investigated. The evolution of chlortoluron concentration with processing time shows a pseudo first order kinetics (k_abs = (4.8 ± 0.2) × 10⁹ mol⁻¹ L s⁻¹). A Doehlert matrix was applied for determination of the optimal working conditions. Optimal parameters for maximum mineralization efficiency (TOC removal ratio of 98%) was achieved after 8 h of treatment using a chlortoluron initial concentration of 0.125 mM and an applied current of 300 mA. The mineralization of aqueous chlortoluron solutions was confirmed by identification of the end-products such as carboxylic acids and inorganic ions. Their evolution during electro-Fenton treatment was studied.     

Study on extraction kinetics of α-cyclopentylmandelic acid enantiomers with hydroxyethyl-β-cyclodextrin as chiral selector

In this work,the kinetic study on reactive extraction ofα-cyclopentylmandelic acid(α-CPMA)enantiomers was performed in a Lewis cell using hydroxyethyl-β-cyclodextrin(HE-β-CD)as chiral selector.The enantioselective complexation equilibrium between HE-β-CD andα-CPMA enantiomers was studied by phase solubility method.The important process parameters affecting the initial extraction rate were separately studied and the reaction rate equations were deduced.The optimal conditions for kinetic study were as follows:stirring speed of 75 r·min~(-1),interfacial area of 12.56 cm~2,pH of 2.5,initial HE-β-CD concentration of 0.05 mol·L~(-1),initialα-CPMA concentration of 5 mmol·L~(-1),and temperature of 278 K.The reaction has been found to be first order inα-CPMA and second order in HE-β-CD with the forward rate constants of 2.056×10~(-3)m~6·mol~(-2)·s~(-1)and 1.459×10~(-3)m~6·mol~(-2)·s~(-1)for(S)-α-CPMA and(R)-α-CPMA,respectively.The complexation equilibrium constants were evaluated as 61 L·mol~(-1) and 117 L·mol~(-1)for(S)-α-CPMA and(R)-α-CPMA,and the intrinsic enantioselectivity is estimated as 1.92.     

粉末活性炭-超滤膜组合工艺去除水中磺胺二甲基嘧啶的研究

研究了PAC和UF组合工艺对水中抗生素类药物SMZ的去除效果。结果表明,在SMZ初始质量浓度为400μg.L-1、PAC投加量为10 mg.L-1、膜回收率为50%时,组合工艺对SMZ去除率可达80%以上;随着SMZ质量浓度和溶液pH的升高,SMZ的去除率呈下降趋势;水中加入5 mmol.L-1Ca2+、20 mmol.L-1Al3+等较高价正离子时,组合工艺对SMZ的去除率分别达到90%、97%,但加入Na+后SMZ去除率反而降低;原水存在1～2 mg.L-1有机物时,SMZ去除率会有很大提升,亲水性强的有机物更利于SMZ的去除。     

Performance evaluation of the incorporation of different wire meshes in between perforated current collectors and membrane electrodeassembly on the Passive Direct methanol fuel cell

Passive Direct methanol fuel cells (DMFC) are more suitable for charging small capacity electronic devices. In passive DMFC, the fuel and oxidant are supplied by diffusion and natural convection process on the anode and cathode sides respectively. Current collectors (CC) play a vital importance in fuel cell performance. This paper presents the combined impact of perforated and wire mesh current collectors (WMCC) on passive DMFC performance. Three types of open ratios of perforated current collectors (PCC), such as 45.40％, 55.40％and 63.40％and two types of wire mesh current collectors with open ratios of 38.70％and 45.40％were chosen for the experimental work. A combination of Taguchi-L9 rule is con-sidered. A combination of three PCC and two WMCC on both anode and cathode was used. Methanol con-centration was varied from 1 mol·L-1–5 mol·L-1 for nine combinations of PCC and WMCC. From the experimental results, it is noticed that the combination of PCC and WMCC with an open ratio of 55.40％ and 38.70％ incorporated passive DMFC produced peak power density at 5 mol·L-1 of methanol concentration. The passive DMFC performance was evaluated in terms of maximum power density and maximum current density. The combined current collectors of PCC and WMCC open ratios of 55.40％+38.70％ have more stable voltage than single PCC of open ratio 63.40％ at 4 mol·L-1 of methanol concentration.     

A study on simultaneous removal of NO and SO2 by using sodium persulfate aqueous scrubbing

Nitric oxide(NO) removal and sulfur dioxide(SO_2) removal by sodium persulfate(Na_2S_2O_8) were studied in a Bubble Column Reactor. The proposed reaction pathways of NO and SO_2 removal are discussed. The effects of temperatures(35–90 °C), Na_2S_2O_8(0.05–0.5 mol·L~(-1)), Fe SO4(0.5–5.0 m mol·L~(-1)) and H_2O_2(0.25 mol·L~(-1))on NO and SO_2 removal were investigated. The results indicated that increased persulfate concentration led to increase in NO removal at various temperatures. SO_2 was almost completely removed in the temperature range of 55–85 °C. Fe~(2+)accelerated persulfate activation and enhanced NO removal efficiency. At 0.2 mol·L~(-1) Na_2S_2O_8 and 0.5–1.0 mmol·L~(-1) Fe~(2+), NO removal of 93.5%–99% was obtained at 75–90 °C, SO_2 removal was higher than 99% at all temperatures. The addition of 0.25 mol·L~(-1) H_2O_2 into 0.2 mol·L~(-1) Na_2S_2O_8 solution promoted NO removal efficiency apparently until utterly decomposition of H2 O2, the SO_2 removal was as high as98.4% separately at 35 °C and 80 °C.     

光敏电芬顿法处理高盐分硝基苯废水

利用光敏电芬顿法降解高浓度、高盐分的有机废水(以硝基苯为例),考察FeSO4浓度、草酸钾浓度、电流强度、初始pH对硝基苯降解效果的影响。结果表明:采用紫外光光敏电芬顿法处理硝基苯废水时,盐分耐受度高,降解速度快。最佳降解条件为FeSO4浓度4.5 mmol/L,草酸钾浓度3.0 mmol/L,电流强度1.5 A,初始pH为2,处理1.5 h后,硝基苯的去除率可达93%。     

微流控芯片测定盐酸倍他司汀片中盐酸倍他司汀

采用微流控芯片非接触电导检测法测定片剂中的盐酸倍他司汀.采用1 mmol·L-1HAc和2 mmol·L-1NaAc(pH 4.5)为缓冲溶液,0.1 mmol·L-1SDS为添加剂,以2.40kV分离电压,10 s进样时间,盐酸倍他司汀2 min内可实现快速分离和检测.盐酸倍他司汀的线性范围为10～140μg·mL-...     

液固半移动床分离废水中铯离子的应用

A liquid solid semi-moving bed with non-mechanical particle transport system is proposed and used for fractionation of cesium ion in wastewater. The particle transport system, which consists of a suction chamber, a mixing chamber, a nozzle and a riser tube, is designed to be controlled completely by hydraulic force. Experiments show that continuous feeding and discharging of resin can be realized by the transport system. The removal of cesium ion from wastewater is realized, The concentration of cesium ion in effluent liquid remains below 0,1g·L^-1 （the initial concentration is 5,3g·L^-1） during the 73 hours＇ experiment. The average exchange capacity of resin discharged from the bed is 0.57mmol,（g dry resin）^-1, which is close to the saturated capacity of 0.65mmol·g^-1. And it is also proved that the non-homogeneity of particle vertical velocity along the radial direction can seriously influence the ion-exchange process.     

Fenton法处理模拟偶氮染料废水的研究

采用Fenton法对模拟偶氮染料废水进行了处理。考察了废水初始pH值、H2O2和Fe2＋投加量、反应时间及反应温度等对模拟染料废水COD去除率的影响。实验结果表明,在甲基红的初始浓度为200mg.L-1,初始pH值为3.0,H2O2和Fe2＋投加量分别为20mmol.L-1和1mmol.L-1,反应温度为50℃,反应时间为60min的条件下,废水中COD的去除率可达83.5%。     

UV/Fe/H2O2体系光解对硝基苯胺废水的实验研究

在自制的光催化反应器中,采用UV/Fe/H2O2体系光解对硝基苯胺(PNA)模拟废水,考察了Fe粉和H2O2投加量、PNA浓度、废水溶液初始pH值等因素对光解过程的影响。实验结果表明,常温条件下,用32 W低压汞灯(λ=254 nm)照射,UV/Fe/H2O2体系降解PNA效果明显,当pH=3.0、Fe投加量为25 mg/L、H2O2投加量为3 mL/L时,100 mg/L模拟对硝基苯胺废水在12 min后PNA降解率达90%以上,溶液CODCr去除率超过50%。     

坡柳皂苷对马铃薯块茎蛾产卵选择性的影响研究

为探明坡柳皂苷对马铃薯块茎蛾产卵行为的影响,以开发生物农药,在室内采用选择性产卵实验方法分别测定了5种不同质量浓度的坡柳皂苷对马铃薯块茎蛾产卵选择性的影响.结果表明：从产卵量来看,各处理组与对照之间差异极显著,其中10.000 g·L-1处理组与对照的落卵量差别较大、卡方位达到131.120,0.080 g·L-1处理组次之、卡方值为92.395,2.000 g·L-1处理组与对照的落卵量差别较小、卡方位仅为24.599;从驱避效果来看,当坡柳皂苷浓度为10.000 g·L-1、0.080 g·L-1时驱避效果较好,驱避引诱指教分别为0.1891、0.1881,但是当坡柳皂苷浓度为0.400 g·L-1时,无驱避效果,驱避引诱指数为-0.1056,其它处理组驱避效果较弱;从整体上来看,坡柳皂苷对马铃薯块茎蛾产卵有驱避作用;坡柳皂苷对马铃薯块茎蛾的交配影响较小,0.016 g·L-1、0.080 g·L-1、0.400 g·L-1、2.000g·L-1、10.000 g·L-1处理组的交配率分别为60.00％、67.50％、67.50％％、67.50％、72.50％.表明,坡柳皂苷对马铃薯块茎蛾具有一定的产卵驱避作用,有望成为一种绿色环保的马铃薯块茎蛾产卵驱避剂.     

UV/H2O2/草酸铁络合物处理水中聚丙烯酰胺

采用UV/H2O2/草酸铁作为氧化剂氧化降解水中的聚丙烯酰胺(PAM)。研究了H2O2投加量、反应时间、n(Fe3+):n(草酸)对PAM降解的影响。试验结果表明,在室温25℃,n(Fe3+):n(草酸)=1:3,H2O2浓度为15 mmol.L-1,pH=3的条件下,光照120 min后,质量浓度为400 mg.L-1的PAM的去除率达到88.3%,与其它光氧化体系相比,去除效果较为明显。     

Degradation of orange G by H2O2、S2O82－、S2O82－-H2O2with ferrous ion

以偶氮染料橙黄G（OG）为目标污染物,研究Fe2+分别催化H2O2、S2O82－、H2O2-S2O82－降解0.1 mmol/L OG Fe2+/H2O2体系,[Fe2+]=1 mmol/L, pH=3, [H2O2]0=10 mmol/L,降解30 min OG脱色率为96%,随着pH值增大和[H2O2]0＞10 mmol/L,OG脱色率减小,呈线性变化。Fe2+/S2O82－体系,随着S2O82－初始浓度增加OG脱色率增大,随着pH值增大OG脱色率减小,呈非线性变化。Fe2+/H2O2-S2O82－体系,pH=3, [H2O2]0=2 mmol/L, [S2O82－]0＞10 mmol/L时OG脱色率持续增大。Fe2+/H2O2-S2O82－体系矿化率最高。利用乙醇和硝基苯作为分子探针,采用分子探针竞争实验鉴定该体系中产生的SO4?和OH?。