Regulation of meilingmycin in Streptomyces nanchangensis: Effect of ammonium ion

Abstract

Effects of different ammonium sulfate concentrations on meilingmycin biosynthesis were studied in this research. The results show that a lower concentration of ammonium ions stimulates the biosynthesis of meilingmycin, while a concentration higher than 5 mmol/L inhibits the mycelial growth and the biosynthesis of the products. However, increased sugar consumption rate with the elevated concentration of ammonium sulfate was observed during the fermentation process. On this basis, six enzymes, which are responsible for the meilingmycin biosynthesis and the glucose metabolism, were measured and analyzed during the bioprocess. The results suggest that glucose-6-phosphate dehydrogenase, citrate synthase, succinate dehydrogenase and fatty acid synthase are stimulated by higher concentration of ammonium ions, while valine dehydrogenase and methylmalonyl-CoA carboxyltransferase are inhibited. From the results it follows that the precursor supply was restricted with the higher concentration of ammonium ions, which results in the lower production of meilingmycin. Thus, the strategy of maintaining a low level of FAS activity is a critical factor for high yield of meilingmycin.

Preparation of Ordered Mesoporous Alumina Supported‐ZnO/NiO Nanocomposite Using Supercritical Carbon Dioxide Impregnation and Its Photocatalytic Performance

“…The two Lorentzian‐Gaussian peaks were used to fit O1s peak in Figure d. The low energy peak around 529.3 eV correspondeds to the metal cations of the structure, and the second binding energy of around 530.7 eV most possible attributes to adsorbed oxygen of OMA . The XPS results confirm that ZnO and NiO exist in the ZnO/NiO/OMA composites.…”

“…On one hand, the strong adsorption of dye molecules can reduce the concentration of the reactants; on the other hand, the ordered mesoporous channels are contributed to the transmission of the reactants, products and the oxygen species. Besides, the well dispersion and small particle sizes of ZnO/NiO are also contributed to photocatalytic activities . In addition, compared with sample 2 and sample 3, sample 4 showed the best performance on the photocatalytic degradation of Congo Red, indicating that there is an optimal mole ratio of ZnO/NiO nanocomposite.…”