Significance and Impact of the Study: Pullulanases have a great potential in industrial applications including the starch industry, the production of maltose syrups and high-purity glucose and fructose. In this study, a pullulanase from hyperthermophilic archaeon Thermococcus kodakarensis KOD1 was successfully expressed in Escherichia coli and the recombinant enzyme can be purified and characterized. The high activity, broad pH range and stability implicate it as a potential enzyme for industrial applications.
AbstractIn this report, a glycoside hydrolase 13 family pullulanase gene (Tk0977) was cloned from a thermophilic anaerobic archaeon Thermococcus kodakarensis KOD1 (Pul-Tk). Pul-Tk encodes a protein of 765 amino acids including a putative 22-residue signal peptide. The protein has four consensus motives and a catalytic triad of glycoside hydrolase 13 family in the deduced amino acid sequence. The recombinant enzyme was expressed in Escherichia coli and purified to homogeneity. Pul-Tk can hydrolyse both pullulan and soluble starch. The purified enzyme was optimal at pH 5Á5-6Á0 and 100°C and exhibited good stability over a broad pH range (4-8). The V max and K m values were 118Á39 AE 1Á76 lmol mg À1 min À1 and 0Á37 AE 0Á02 mg ml À1 for pullulan and 53Á19 AE 11Á66 lmol mg À1 min À1 and 0Á36 AE 0Á05 mg ml À1 for starch.All these favourable enzymatic properties make it valuable in various industries.
Characteristic response parameterized in time-dependent target intrinsic polarizabilities can be used to discriminate unexploded ordnance (UXO) from harmless items. This study explains the measurement, analysis, and classification of UXO-like targets against data collected under laboratory-type conditions with a specially designed transient electromagnetic (TEM) system. After a brief description of the single dipole model and TEM system, the characteristic responses of all UXO-like targets have been measured with an improved long straight solenoid. The influence of the target shape and size on characteristic response is analyzed. Results show that targets of the same shape share similar power law function decay rate at an early time. The larger the target size is, the greater the response will be. The characteristic response for harmless targets decays faster than the UXOs, leading to a considerable difference in a later time, which can be used for target classification. When the characteristic response is parameterized as kt −β e −γ t in 100 ms, targets can be effectively separated with the fitted parameters k, β and γ. However, when fitted in 10 ms, the fitted parameter γ may be thousands of times than the one fitted in 100 ms, resulting in classification failure. The normalized response combined with the fitting parameter β can be used for target classification to overcome the instability of fitted parameter γ in 10 ms. Finally, all UXOs are completely separated from harmless targets within 10 ms.
K: Data processing methods; Detection of explosives; Pattern recognition, cluster finding, calibration and fitting methods 1Corresponding author.
The melting temperature-pressure phase diagram [Tm(P)-P] for corundum (Al2O3), wustite (FeO) and magnesium oxide (MgO) are predicted through the Clapeyron equation where the pressure-dependent volume difference is modeled by introducing the effect of surface stress induced pressure. The model prediction is found to be consistent with the present experimental results.
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