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Abstract: A novel enzymatic organic synthesis was reported, utilizing glucose-3-dehydrogenase (G3DH) and its regeneration via electrochemical methods. We combined the water-soluble G3DH prepared from a marine bacterium, Halomonas sp. α-15, and electron mediator with the electrode system in order to regenerate the enzyme. Using this system, the conversion of 1,5-anhydro-d-glucitol (1,5AG), a diabetes marker in human blood, was investigated. The final yield of the product, 3-keto anhydroglucitol (3-ketoAG), which was identified by 13C nuclear magnetic resonance, was 82% based on the initial amount of 1,5AG. The electrochemical yield of the reaction proceeded almost stoichiometrically. The electrochemical conversion rate of 1,5AG was 1.24 mmol/(L�h), and the electrochemical yield of 1,5AG consumption was 80%, whereas that for 3-ketoAG was 60%.

A photobioreactor was constructed in the form of a Perspex column 900 mm tall with an internal diameter of 70 mm. The reactor volume was 1.8 L and the light source consisted of a metal-halide lamp to reproduce sunlight. Light was distributed through the culture using a new type of optical fiber that diffuses light out through its surface, perpendicular to the fiber axis. A cluster of 661 light-diffusing optical fibers (LDOFs) pass from the light source through the reactor column (60-cm culture depth) and are connected to a mirror at the top of the reactor. This biosolar reactor has been used for the production of glutamate from CO2by the marine cyanobacterium Synechococcus sp. NKBG040607. We present here details of the construction of the biosolar reactor and characterization of its properties. The effect of light intensity on glutamate production was measured. Carbon dioxide-to-glutamate conversion ratios were determined at different cell densities: the maximum conversion ratio (28%) was achieved at a cell density of 3x108cells/mL. A comparison of glutamate production using the LDOF biosolar reactor described here with production by batch culture using free or immobilized cells showed that use of an optical-fiber biosolar reactor increased glutamate-production efficiency 6.75-fold. We conclude that as a result of its high surface-to-volume ratio (692/m) increased photoproduction of useful compounds may be achieved. Such a system is generally applicable to all aspects of photobiotechnology.

The aim of this work is to elucidate the iron uptake mechanism in the magnetic bacteriumAquaspirillumsp. AMB-1, which can utilize a wide variety of iron chelates. However, no siderophore could be detected in spent culture. A 400-bp DNA fragment was amplified by polymerase chain reaction (PCR) from the genomic DNA of AMB-1, using primers designed from thesfuCgene ofSerratia marcescens. This gene encodes a nucleotide binding protein in the periplasmic binding protein (PBP) dependent iron transport system. The amplified fragment was homologous with the conserved sequence ofsfuC. Our results suggest that a nucleotide binding protein mediated iron transport system similar to that observed inSerratia marcescensis present inAquaspirillumsp. AMB-1.

A light diffusing optical fiber (LDOF) photobioreactor with an improved gas input system has been used for the high-density culture of a marine cyanobacterium Synechococcus sp. Optimum conditions for CO2 removal and biomass production were investigated. Maximum CO2 removal of 4.44 g/L/d was achieved using an initial cell concentration of 6.8 g/L. The biomass yield was 0.97 g/L for a 12-culture time. Continuous cultures, in which medium was filtered using a ceramic membrane module, showed enhanced growth, with a final cell concentration of 11.2 g/L. These results demonstrate the potential of LDOF photobioreactor units for CO2 removal and biomass production using marine cyanobacteria.

Endo-pectate lyase (PATE) fromErwinia carotovorawas selectively cosedimented with extracellularly produced lipopolysaccharide-lipid complex (LPSLC) through dialysis of the cell free culture broth. The selective isolation of PATE was confirmed by sodium dodecyl sulfate polyacrylamide gel electrophoresis. The cosedimentation of the PATE with LPSLC was initiated by decreasing conductivity of the solution and terminated at approx 1 m Siemens (mScm-1). As much as 62% of PATE activity in the culture broth was removed by precipitation. PATE was isolated from the precipitate by gel chromatography. The cosedimentation of PATE with LPSLC was remarkably affected by pH or ionic strength. The addition of polycationic peptide polymyxin B sulfate or a metal chloride affected the interaction. The cosedimentation was diminished by acetylation of the free amino groups of PATE. From these results, it was confirmed that the cosedimentation was induced by electrostatic interaction.

Microbial conversion of 4-oxoisophorone (OIP) by thermophilic bacteriumThermomonospora curvatawas attempted in a continuous process.

Citrobacter freundiigenes that complementedEscherichia colihyd(hydrogenase activity) mutation were cloned in plasmids pCBH4 (6.2 kb) and pCBH6(5.7 kb) (1,2). Hydrogen evolution by the transformantE. coliHK-8(pCBH4 or pCBH6) was investigated. The optimum culture temperature of recombinantE. colicells for hydrogen evolution from glucose was in the neighborhood of 18°C. The recombinantE. colicells cultured at this condition showed a several-fold increase of hydrogen evolution, as compared with that of the wild-type cells. The plasmid-retention stability of this recombinantE. coliwas extremely high, especially plasmid pCBH4, which was completely retained during 2 wk without any restriction. Hydrogen production by immobilized recombinantE. coliwas then investigated using cells cultured at 18°C. The hydrogen evolution rate from glucose and Lennoxbroth were about twofold higher than that ofE. coliC600, and this high hydrogen evolution rate was maintained for more than 1 mo.

A novel glucose dehydrogenase (GDH) from a marine bacteriumCytophaga marinoflavaIFO 14170 was isolated from its membrane fraction. This GDH catalyzes the oxidation of a hydroxy group of glucose, but does not react in its C-l position. This enzyme is composed of a single peptide with a mol wt of 67,000. The GDH can react under high salinity. The optimum pH is around 8.0, showing a typical property of marine bacterial enzymes. Using this novel enzyme, an enzymatic determination of 1,5-anhydro-D-glucitol (1,5AG) utilizing 2,6-dichrolophenolindophenol (DCIP) and phenazine methosulfate (PMS) as electron mediators was caried out. A good linear correlation was observed from 0.5 mMto 4 mMof 1,5AG.