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What is known as the One Child Policy was introduced in 1979 as a set of rules and regulations governing the approved size of Chinese families. This was not the [...]

This study was conducted to determine the optimum active site of acidic phytase in the gastrointestinal tract of channel catfish. The pH value, acidic phytase activity, resistance of acidic phytase against gastrointestinal protease, substrate availability, and enzymatic reaction products were measured in different gastrointestinal sections of channel catfish, respectively. The results indicated that in the whole gastrointestinal tract, only the pH value of stomach (4.2- 4.7) lied in the optimum active pH range of acidic phytase (1.5-5.5). The resistant ability of acidic phytase against proteases in different sections of the gastrointestinal tract was comparable, and the highest activity of phytase was observed in the stomach compared with other gastrointestinal sections. Moreover, the highest concentration of soluble phytic acid as the substrate of phytase was also seen in the stomach. After feeding fish with the diet containing acidic phytase, the residual phytic acid in the stomach was significantly reduced. Correspondingly, the dietary addition of acidic phytase significantly improved the phosphorus absorption in the intestine. In short, this study verified that stomach is the optimum active site for acidic phytase in channel catfish, because it allows higher phytase activity and provides more soluble substrates of phytase than other gastrointestinal sections. [ABSTRACT FROM AUTHOR]

In comparison to Ru catalysts supported on activated carbon (AC), MgO, Al2O3, and TiO2 under similar reaction conditions, Ru catalyst using carbon nanotubes as support (Ru/CNTs) was found to show high NH3 conversion for the generation of COx-free hydrogen from NH3. The modification of the catalyst with KOH leads to a significant improvement in activity, either in term of NH3 conversion or TOF. The Ru/CNTs catalyst prepared from acetone solvent is more active than that from water solvent, and the use of the former leads to an increase in Ru dispersion and a decrease in residual Cl concentration. The results of H2-TPD and HRTEM characterization disclosed that the excellent catalytic activity of Ru/CNTs could be ascribed to the high dispersion of Ru particles, and to the high graphitization and high purity of the CNTs material. The residual Cl originated from the RuCl3 precursor was found to be a strong inhibitor for the decomposition reaction. Once the residual Cl is in the form of KCl, it is difficult to remove. The results of N2-TPD studies imply that the desorption of N2 is the rate-determining step, and the modification with KOH leads to a decrease in N2 desorption temperature and in apparent activation energy of NH3 decomposition over Ru/CNTs. [Copyright &y& Elsevier]