Regulatory effects of ammonium ions on the biosynthesis of meilingmycin

Based on the effects of different ammonium sulfate concentrations on meilingmycin biosynthesis, the results show that lower concentration of ammonium ions stimulates the biosynthesis of meilingmycin, while the concentration of higher than 5mmol/L inhibits the mycelial growth and the biosynthesis of the products. However, the sugar consumption rate increases with the elevating concentration of ammonium sulfate. On this basis, six enzymes, which are greatly related to the meilingmycin biosynthesis and the glucose metabolism, were measured and analyzed during the meilingmycin fermentation process. 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 ammonium ions favors primary metabolism, that is, the HMP passway and the TCA circle is enhanced, as well as the source of the precursors for the biosynthesis of meilingmycin is restricted, which bring about the lower production of meilingmycin.