Erratum to: Comprehensive interrogation of electrochemical reaction and energy conversion of a direct fucose fuel cell

Journal of Solid State Electrochemistry - In this research, we conducted a comprehensive interrogation of a direct fucose fuel cell to maximise the electric power and demonstrated the potential for...     

Alcohol sensor based on membrane-bound alcohol dehydrogenase

Ethanol is determined by a sensor system using purified, immobilized mernbrane-bound alcohol dehydrogenase frorn Gluconobacter suboxydans, attached to a platinum disk electrode (3 mm diameter), and covered with a dialysis membrane. Hexacyanoferrate (III) is used as the redox acceptor. To correct for the influence of interfering substances, this alcohol sensor is compensated by a control electrode which has no immobilized enzyme. The potential of these platinum electrodes was set at + 350 mV vs. Ag/AgCl. Linearity was observed in the range 0.1–5 mM ethanol, the response time was less than 5 min, the maximum sensitivity was obtained at 45°C and the optimum pH was in the range 4.5–5.5. The sensitivity decreased to 80% of the initial value after 1 month at 30°C. When the alcohol sensor system was applied to the determination of ethanol in alcoholic beverages, a good correlation was obtained between the results and those obtained by gas chromatography.     

Total Syntheses of Amphidinolides B1, B4, G1, H1 and Structure Revision of Amphidinolide H2

Nature is a pretty unselective “chemist” when it comes to making the highly cytotoxic amphidinolide macrolides of the B/G/H series. To date, 16 different such compounds have been isolated, all of which could now be approached by a highly convergent and largely catalysis‐based route (see figure). This notion is exemplified by the total synthesis of five prototype members of this family.

     

Microbial detection of toxic compounds utilizing recombinant DNA technology and bioluminescence

A microbial sensing system was developed utilizing recombinant DNA technology for the determination of environmental pollutants. The emission of light in Escherichia coli was achieved by cloning the genes encoding luciferase from firefly and by injection of the luminescence substrate luciferin. A good correlation was observed between increased luminescence and the concentration of luciferin. Measurement of environmental pollutants was based on the decrease of in vivo luminescence intensity emitted by recombinant E. coli, which was affected by cell metabolic inactivator. Environmental pollutants such as sodium azide and fluoroacetic acid, which are components of ATP-inhibiting pesticides, and antibiotics were detected at or below the μg ml^?1 level by this system by measurement of the decrease in in vivo luminescence.     

An amperometric sensor for carbon dioxide based on immobilized bacteria utilizing carbon dioxide

A biosensor consisting of a CO₂-utilizing autotrophic bacterium (strain S-17, Pseudomonas type) and an oxygen-sensing electrode was constructed for the amperometric determination of CO₂. The correlation between current decrease and CO₂ concentration was linear in the range 5–200 mg l^?1 CO₂. The optimum temperature and pH for operation of the biosensor were 30°C and 5.5, respectively. The sensor did not respond to other volatile compounds except for acetic acid. The sensor could be operated continuously for about a month.     

A rapid label-free electrochemical detection and kinetic study of Alzheimer's amyloid beta aggregation

We present the first electrochemical detection, characterization, and kinetic study of the aggregation of Alzheimer's disease (AD) amyloid beta peptides (Abeta-40, Abeta-42) using three different voltammetric techniques at a glassy carbon electrode (GCE). This method is based on detecting changes in the oxidation signal of tyrosine (Tyr) residue. As the peptides aggregate, there are structure conformational changes, which affect the degree of exposure of Tyr to the molecular surface of the peptides. The results show significant differences in the aggregation process between the two peptides, and these correlate highly with established techniques. The method is rapid and label-free, and the principle can be universally applied to other protein aggregation studies related to diseases, such as Huntington's, Parkinson's, and Creutzfeldt Jacob (CJD). This method could also be explored in screening for the effectiveness of AD therapies.     

Alcohol-FET sensor based on a complex cell membrane enzyme system

An alcohol -FET sensor was developed by use of a complex enzyme system in a cell membrane and an ion-sensitive field effect transistor (ISFET). The cell membrane of Gluconobacter suboxydans IFO 12528, which converts ethanol to acetic acid, was immobilized on the gate of an ISFET with calcium alginate gel coated with nitrocellulose. This ISFET (1), a reference ISFET without the cell membrane (ISFET 2) and an Ag/AgCl reference electrode were placed in 5 mM Trismalate buffer (pH 5.5, 25°C), and the differential output between ISFETS 1 and 2 was measured. The output of the sensor was stabilized by adding pyrroloquinoline quinone. The response time was ca. 10 min., and there was a linear relationship between the differential output voltage and the ethanol concentration up to 20 mg l^?1. The output of the sensor was stable for 40 h below 30°C. The sensor responded to ethanol, propan- 1-ol and butan- 1-ol, but not to methanol, propan-2-ol and butan-2-ol. The sensor was used to determine blood ethanol.     

Application of microbiological sensors in fermentation processes

A review is presented of microbiological sensors which are composed of micro-organisms immobilized in a membrane and coupled to a sensing element. Conventional microbiological sensors such as those for biochemical oxygen demand (BOD), ethanol and acetic acid are discussed briefly. Novel sensors are then described. The sensor for carbon dioxide is based on a chemoautotrophic bacterium, that for alcohol on cell membranes of the acetic acid bacteria, Gluoconabacter suboxydans. Sensors for BOD carbon dioxide are based on thermophilic bacteria. Finally, a microbial field effect transistor sensor (FET) for alcohol sensor is described. For all the sensors, the ranges of linear response and their long-term stabilities are reported.     

An electrochemical on-field sensor system for the detection of compost maturity

A maturity sensor system was developed, based on the combination of three electrically measured parameters, pH, NH₄⁺ concentration, and phosphatase activity in the water extracts of compost samples. One of these parameters, the apparent phosphatase activity in crude test solutions was determined using screen-printed carbon strips (SPCSs) coated with α-naphthyl phosphate (α-NP) in Nafion film. The phosphatase activity was monitored in connection with differential pulse voltammetry (DPV) with an aliquot (30 μL) of the test solution on SPCS. The phosphatase activity sensor was validated using alkaline phosphatase (ALP) in Tris-HCl buffer (pH 8.0) and acid phosphatase (ACP) in citric acid buffer (pH 5.0). The activity of the spiked enzymes in the water extract of the compost sample could be confirmed with the change of corresponding oxidation peak current signal of the product, α-naphthol. The water extracts of compost samples (n = 24) collected in various composting days were applied to our compost maturity sensor system, and the conventional germination tests. Using multiple regression analysis, the germination index (GI) was expressed by the multi-linear regression equation consisting of pH, NH₄⁺ concentration, and the phosphatase activity. The calculated GI from the regression equation had a good correlation with the measured GI of the corresponding composts (r = 0.873). As a result, we have determined an equation for the determination of the compost stability using our portable sensor system rapidly at the composting site.