RESUMEN
High levels of extracellular xylanase activity (211.79 IU/mg) produced by Paenibacillus sp. NF1 were detected when it was submerged-cultured. After three consecutive purification steps using Octyl-Sepharose, Sephadex G75, and Q-Sepharose columns, a thermostable xylanase (XynNF) was purified to homogeneity and showed a molecular mass of 37 kDa according to SDS-PAGE. The specific activity of the purified XynNF was up to 3,081.05 IU/mg with a 14.55-fold purification. The activity of XynNF was stimulated by Ca(2+), Ba(2+), DTT, and ß-mercaptoethanol, but was inhibited by Fe(3+), Zn(2+), Fe(2+), Cu(2+), SDS, and EDTA. The purified XynNF displayed a greater affinity for oat spelt xylan with the maximal enzymatic activity at 60°C and pH 6.0. XynNF, which was shown to be cellulose-free, with high stability at high temperature (70°C-80°C) and low pH range (pH 4.0-7.0), is potentially valuable for various industrial applications. The end products of high efficient oat spelt xylan hydrolysis by XynNF (an endoxylanase) containing 95.8% xylooligosaccharides of 2-4 degree of polymerization (DP2-4) with the enrichment of xylobiose (61.5%) indicated that XynNF is a promising candidate for xylooligosaccharides production.
Asunto(s)
Glucuronatos/metabolismo , Oligosacáridos/metabolismo , Paenibacillus/enzimología , Xilosidasas/química , Xilosidasas/metabolismo , Avena/química , Cromatografía Liquida/métodos , Electroforesis en Gel de Poliacrilamida , Activadores de Enzimas/análisis , Inhibidores Enzimáticos/análisis , Estabilidad de Enzimas , Concentración de Iones de Hidrógeno , Hidrólisis , Peso Molecular , Temperatura , Xilanos/metabolismo , Xilosidasas/aislamiento & purificaciónRESUMEN
We propose a novel metal artifact reduction method based on a fractional-order curvature driven diffusion model for X-ray computed tomography. Our method treats projection data with metal regions as a damaged image and uses the fractional-order curvature-driven diffusion model to recover the lost information caused by the metal region. The numerical scheme for our method is also analyzed. We use the peak signal-to-noise ratio as a reference measure. The simulation results demonstrate that our method achieves better performance than existing projection interpolation methods, including linear interpolation and total variation.
Asunto(s)
Artefactos , Modelos Teóricos , Interpretación de Imagen Radiográfica Asistida por Computador/métodos , Tomografía Computarizada por Rayos X/métodos , Algoritmos , Relación Señal-RuidoRESUMEN
In this paper, we propose a new metal artifacts reduction algorithm based on fractional-order total-variation sinogram inpainting model for X-ray computed tomography (CT). The numerical algorithm for our fractional-order framework is also analyzed. Simulations show that, both quantitatively and qualitatively, our method is superior to conditional interpolation methods and the classic integral-order total variation model.
