Sphaerotilus natans isolated from activated sludge and its production of poly (3-hydroxybutyrate-co-3-hydroxyvalerate)

Sphaerotilus natans is a sheathed bacterium existing in the activated sludge of wastewater treatment plants. IT is one of the filamentous bacteria causing the bulking and foaming difficulties of activated sludge. Isolating the strain and culturing it in an axenic environment could not only provide the metabolic knowledge of the strains that would be useful in the development of wastewater treatment methods, but also could enable us to gain an understanding of the mechanism by which poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (poly[3-HB-co-3-HV]) is produced by this strain. This article reports the screening and isolation of the strain from the activated sludge using the Nile blue staining method together with Fourier transform infrared analysis. We investigated the ability of the selected strain to produce poly(3-HB-co-3-HV) copolymer using glucose and peptone, or by adding valeric acid or sodium propionate as precursor. Proper precursor feeding could dramatically enhance its 3HV content in the copolymer P(3HB-co-3HV). By controlling the different feeding times in fed-batch fermentation, different desired copolymers were obtained with 15, 40, and 70% 3HV mole fraction of the copolymer. Polymer properties were analyzed by gas chromatography, differential scanning calorimetry, thermo-gravimetry, and nuclear magnetic resonance analysis. Open laboratory of Chirotechnology of the Institute of Molecular Technology for Drug Discovery and Synthesis The University Grants Committee Area of Excellence Scheme (Hong Kong).     

Tunable Fiber Ring Laser Employing a Sagnac Interferometric Filter

A tunable erbium-doped fiber ring laser employing an all -polarization- maintaining fiber loop filter with certain birefringence is proposed and demonstrated. The lasing frequencies can be selected by properly adjusting the polarization controller in the cavity.     

Optical waveguiding in semiconductor injection lasers and integrated optics

Weak perturbations from various refractive index distributions have been introduced into the central layer of the three layered dielectric slab optical waveguide model and solutions of the wave equation in this guide for TE modes have been compared with the results published for the unperturbed mode. The perturbations in general introduce quadrature components in the transverse modes and a mode width dependent amplitude. The mode position within the guide can be shifted and the mode width increased or decreased. With increasing parabolic perturbation there is increasing waveguide discrimination against higher order modes.     

Weighted Sobolev Interpolation Inequalities on Certain Domains

We obtain some weighted Sobolev interpolation inequalities oncertain domains that include Lipschitz domains for doublingweights satisfying a weighted Poincaré inequality. Thesegeneralize most results in Gutierrez and Wheeden's paper [20].We also give some applications on Lipschitz domains for weightsof type dist (·, G)⁸, where G .     

Conversion of food industrial wastes into bioplastics

The usage of plastics in packaging and disposable products, and the generation of plastic waste, have been increasing drastically. Broader usage of biodegradable plastics in packaging and disposable products as a solution to environmental problems would heavily depend on further reduction of costs and the discovery of novel biodegradable plastics with improved properties. In the authors’ laboratories, various carbohydrates in the growth media, including sucrose, lactic acid, butyric acid, valeric acid, and various combinations of butyric and valeric acids, were utilized as the carbon (c) sources for the production of bioplastics byAlcaligenes eutrophus. As the first step in pursuit of eventual usage of industrial food wastewater as nutrients for microorganisms to synthesize bioplastics, the authors investigated the usage of malt wastes from a beer brewery plant as the C sources for the production of bioplastics by microorganisms. Specific polymer production yield by A. Latus DSM 1124 increased to 70% polymer/cell (g/g) and 32g/L cell dry wt, using malt wastes as the C source. The results of these experiments indicated that, with the use of different types of food wastes as the C source, different polyhydroxyal-kanoate copolymers could be produced with distinct polymer properties.     

Adhesion of Pseudomonas fluorescens on magnetic surfaces

The adhesion of Pseudomonas fluorescens (ATCC 700830) to perpendicularly polarized magnetic surfaces was recently discovered. The findings have found that the magnetic free surfaces from different magnetic polarities have different profound effects on the P. fluorescens bacterial adhesion to its surfaces. These phenomena can be explained by the surface magnetic effect, which was found to affect the surface free energy. An in situ experiment, by contrast microscopy and under static conditions, was conducted to determine the influence of magnetic surfaces, that are polarized under different external magnetizing field strengths, on bacterial adhesion. The effect of different magnetic polarities on the surface free energy has also been investigated.