Improved performance of membrane free single-chamber air-cathode microbial fuel cells with nitric acid and ethylenediamine surface modified activated carbon fiber felt anodes

Surface modifications of anode materials are important for enhancing power generation of microbial fuel cell (MFC). Membrane free single-chamber air-cathode MFCs, MFC-A and MFC-N, were constructed using activated carbon fiber felt (ACF) anodes treated by nitric acid and ethylenediamine (EDA), respectively. Experimental results showed that the start-up time to achieve the maximum voltages for the MFC-A and MFC-N was shortened by 45% and 51%, respectively as compared to that for MFC-AT equipped with an unmodified anode. Moreover, the power output of MFCs with modified anodes was significantly improved. In comparison with MFC-AT which had a maximum power density of 1304 mW/m², the MFC-N achieved a maximum power density of 1641 mW/m². The nitric acid-treated anode in MFC-A increased the power density by 58% reaching 2066 mW/m². XPS analysis of the treated and untreated anode materials indicated that the power enhancement was attributable to the changes of surface functional groups.     

(Ni-Sn-M_xO_y)/Pb改性复合电极电解合成L-半胱氨酸的反应

在（Ｎｉ－Ｓｎ）／Ｐｂ合金修饰电极中添加某些金属氧化物进行改性,用于电解合成Ｌ－半胱氨酸反应。结果证明,添加ＷＯ３后电极反应活性大大加强,反应同期转化率有较大提高,选择性也有所提高,添加稀土金属氧化物能有效降低反应阴极过电位,使反应选择性有所提高,但是电极稳定性还有待改善。     

“共轭聚合物-产电菌”复合生物电极构建及其在微生物燃料电池中的应用

微生物燃料电池(Microbial fuel cell,MFC)作为一种生物电化学装置,在可再生能源生产和废水处理方面的巨大潜力已引起广泛关注。然而MFC面临输出功率低、欧姆内阻高以及启动时间长等问题,极大限制了其在实际工程中的应用。MFC中阳极是微生物附着的载体,对电子的产生及传递起着关键作用,开发优质的生物电极已发展成为改善MFC性能的有效途径。共轭聚合物具有成本低、电导率高、化学稳定性及生物相容性好等优点,利用共轭聚合物修饰生物电极结构,可以实现大比表面积、缩短电荷转移路径,从而实现高效生物电化学性能。同时,纳米级共轭聚合物包覆细菌,可以使细菌产生的电子有效地传递到电极。文中综述了最近报道的共轭聚合物在MFC中的应用,重点介绍了共轭聚合物修饰的MFC阳极,系统分析了共轭聚合物的优点及局限性,以及这些高效复合生物电极如何解决MFC应用中存在的低输出功率、高欧姆内阻及长启动时间等问题。     

The respiratory chain of plant mitochondria. XV. Equilibration of cytochromes c549, b553, b557 and ubiquinone in mung bean mitochondria: Placement of cytochrome b557 and estimation of the midpoint potential of ubiquinone

1. 1. Cycles of oxidation followed by reduction at pH 7.2 have been induced in uncoupled anaerobic mung bean mitochondria treated with succinate and malonate by addition of oxygen-saturated medium. Under the conditions used, cytochromes b₅₅₇, b₅₅₃, c₅₄₉ (corresponding to c₁ in mammalian mitochondria) and ubiquinone are completely oxidized in the aerobic state, but become completely reduced in anaerobiosis.

2. 2. The time course of the transition from fully oxidized to fully reduced in anaerobiosis was measured for cytochromes c₅₄₉, b₅₅₇, and b₅₅₃. The intramitochondrial redox potential (IMP_h) was calculated as a function of time for each of the three cytochromes from the time course of the oxidized-to-reduced transition and the known midpoint potentials of the cytochromes at pH 7.2. The three curves so obtained are superimposable, showing that the three cytochromes are in redox equilibrium under these conditions during the oxidized-to-reduced transition.

3. 3. This result shows that the slow reduction of cytochrome b₅₅₇ under these conditions, heretofore considered anomalous, is merely a consequence of its more negative midpoint potential of +42 mV at pH 7.2, compared to +75 mV for cytochrome b₅₅₃ and +235 mV for cytochrome c₅₄₉. Cytochrome b₅₅₇ is placed on the low potential side of coupling site II and transfers electrons to cytochrome c₅₄₉ via the coupling site.

4. 4. The time course of the transition from fully oxidized to fully reduced was also measured for ubiquinone. Using the change in intramitochondrial potential IMP_h with time obtained from the three cytochromes, the change in redox state of ubiquinone with IMP_h was calculated. When replotted as IMP_h versus the logarithm of the ratio (fraction oxidized)/(fraction reduced), two redox components with n = 2 were found. The major component is ubiquinone with a midpoint potential E_m7.2 = + 70 mV. The minor component has a midpoint potential E_m7.2 = − 12 mV; its nature is unknown.

环形电极介导的小麦基因转化

用环形电极电激法有效地将外源DNA导入完整的小麦幼胚组织中。电激的物理参数采用770V／cm场强、800μF电容、100μg／mL质粒DNA(含有bar和GUS双标记基因),幼胚被电激3次。经PCR和Southern杂交分析表明,外源基因已稳定整合到小麦基因组中,转化频率为7．5％,高于相同处理条件下基因枪法的转化频率(4．2％)。     

鸽子慢性电刺激用电极转接装置及其固定方法

慢性电极植入以及无线刺激技术被广泛应用于动物自由活动状态下的脑区功能研究。实现刺激器与脑内植入电极过渡连接的转接装置需固定在颅骨之上。鸟类特殊的骨质构造不利于转接装置的长期固定。以鸽子(Columba livia)为例设计制作了一种用于慢性运动诱导实验的9通道电极转接装置,长12.8 mm、宽9.5 mm、高5.5 mm,重0.42 g;根据鸽子颅骨特点在固定过程中对颅骨表面进行粗糙化处理增加固定时与牙科水泥的接触面积,并选取特定位点拧入螺钉进行固定,有效延长了转接装置的固定时间。经实验验证能够在鸽子头部稳定固定6个月以上,满足鸽子长期运动诱导研究的需求,未对动物正常活动产生影响。该装置及其固定方法亦可为其他小型动物的脑区功能研究提供借鉴。     

葡萄糖测定方法的比较研究

比较了传统斐林定糖,葡萄糖氧化酶－过氧化物酶比色法,葡萄糖氧化酶电极自动分析仪法测定葡萄糖。比较测定了的结果显示,三法的平均标准误差（ＳＤ）,变异系数（ＣＶ）均十分接近。通过对此三种方法的回归相关性分析显示：斐林法－酶终点比色法的回归方程为ｙ＝０．９８４３ｘ＋６．３２３９,相关系数Ｒ＾２＝０．９９８９,斐林法－自动分析仪法的回归方程为ｙ＝１．００８８ｘ＋２．０４８３,相关系数Ｒ＾２＝０．９９９１,     

Improved strategies for electrochemical 1,4-NAD(P)H2 regeneration: A new era of bioreactors for industrial biocatalysis

Industrial enzymatic reactions requiring 1,4-NAD(P)H₂ to perform redox transformations often require convoluted coupled enzyme regeneration systems to regenerate 1,4-NAD(P)H₂ from NAD(P) and recycle the cofactor for as many turnovers as possible. Renewed interest in recycling the cofactor via electrochemical means is motivated by the low cost of performing electrochemical reactions, easy monitoring of the reaction progress, and straightforward product recovery. However, electrochemical cofactor regeneration methods invariably produce adventitious reduced cofactor side products which result in unproductive loss of input NAD(P). We review various literature strategies for mitigating adventitious product formation by electrochemical cofactor regeneration systems, and offer insight as to how a successful electrochemical bioreactor system could be constructed to engineer efficient 1,4-NAD(P)H₂-dependent enzyme reactions of interest to the industrial biocatalysis community.     

Qualitative (sunlight) and quantitative (xenon light source) aspects of the photochemistry of [S2W18O62] in the presence of electron donors

The photoelectrochemical properties of the polyoxotungstate anion [S₂W₁₈O₆₂]⁴⁻ dissolved in acetonitrite have been surveyed. Qualitative studies revealed that the rate of oxidation of the electron donor in the presence of sunlight correlated well with the voltammetric peak potential for oxidation of the electron donor at a glassy carbon electrode. Quantitative studies on the photooxidation of tetrahydrofuran, dimethylformamide, triphenylphosphine and ferrocene, as detected at a platinum channel electrode in the presence of a xenon light source, were assigned to a CE mechanism. Simulated fits for the proposed mechanism provide estimates of the reaction rates and data are compared with those obtained previously on the basis of a CECE scheme for the molybdenum analogue.