Browsing by Author "Wu, WT"

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Bioconversion with whole cell penicillin acylase in aqueous two-phase systems
(1999-07-01)
Liao, LC
;
Ho, CS
;
Wu, WT
;
生物科技學系
;
Department of Biological Science and Technology
The deacylation of Pen G was carried out by using recombinant E. coli in an aqueous two-phase system consisting of polyethylene glycol and potassium phosphate solution, which partitions the cells to the bottom phase and the products to the top phase. Bioconversion and product separation were carried out in the same reactor. Repeated batch conversion was employed ten times and enzymic activity showed only a slight decline. When pure enzyme was used for bioconversion in an aqueous two-phase system, the decline was fast and bioconversion using whole cell penicillin acylase was better than that obtained using the pure acylase. (C) 1999 Elsevier Science Ireland Ltd. All rights reserved.
Efficient UV photoluminescence from monodispersed secondary ZnO colloidal spheres synthesized by sol-gel method
(2005-04-15)
Cheng, HM
;
Hsu, HC
;
Chen, SL
;
Wu, WT
;
Kao, CC
ZnO colloidal spheres were synthesized by sol-gel method with a narrow size distribution. We controlled the size of the spheres during the secondary reaction with various amounts of primary reaction supernatant. The optimized condition of ZnO powders with an average diameter of 185 nm was obtained for structure analysis and study of optical properties. Transmission electron microscopy and X-ray diffraction reveal that the spheres are polycrystalline in the pure wurtzite phase. Markedly enhanced near-band-edge ultraviolet pbotoluminescence and significantly reduced defect-related visible emission were also observed. We attribute this observation to the localized bound excitons with high density of defect states. In addition, broad yellow emission and green emission were observed when the powders were post-annealed at 500 degrees C in air ambience. The origins of the defect-induced visible emissions are attributed to oxygen interstitials and oxygen vacancies. (c) 2005 Elsevier B.V. All rights reserved.