Leung P-H, Wu J-Y
Department of Applied Biology & Chemical Technology, the Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong.
J Appl Microbiol. 2007 Nov;103(5):1942-9. doi: 10.1111/j.1365-2672.2007.03451.x.
To examine the effects of ammonium feeding on the production of cordycepin (3'-deoxyadenosine, a nucleoside analogue) and exopolysaccharides (EPS) in mycelial culture of a new Cordyceps sinensis fungus Cs-HK1.
Cs-HK1 fungus was cultivated in a liquid medium containing glucose, yeast extract, peptone and a few major inorganic salts. NH(4)Cl was fed to the mycelial culture at various concentrations from 5 to 40 mmol l(-1) on day 3 (during exponential phase). NH(4)Cl, fed at 10 mmol l(-1), stimulated the cordycepin production most significantly, with nearly fourfold increase in the cordycepin content of mycelia (from 28.5 to 117 microg g(-1)), and also increased the EPS production by 40% (from 2.6 to 3.7 g l(-1)). The ammonium feeding had a slightly positive effect at 5-10 mmol l(-1), but a negative effect at higher concentrations on the mycelium growth. Ammonium feeding also caused a sharp drop of the medium pH, owing perhaps to the uptake of NH(3) and the release of H(+) by the fungal cells.
Ammonium feeding to the mycelial culture of Cs-HK1 fungus enhanced the intracellular cordycepin accumulation and the EPS production. The enhanced cordycepin production may be attributed to the uptake of ammonia for nucleoside synthesis, and the enhanced EPS to the increased uptake of glucose for EPS biosynthesis.
It is useful for the production of bioactive metabolites and for understanding ammonium metabolism and its relationship to the biosynthesis of nucleosides in a precious medicinal fungus.
研究铵添加对新型中华虫草菌Cs-HK1菌丝体培养中虫草素（3'-脱氧腺苷，一种核苷类似物）和胞外多糖（EPS）产生的影响。
Cs-HK1菌在含有葡萄糖、酵母提取物、蛋白胨和几种主要无机盐的液体培养基中培养。在第3天（指数生长期）向菌丝体培养物中添加不同浓度（5至40 mmol l(-1)）的NH(4)Cl。以10 mmol l(-1)添加NH(4)Cl时，对虫草素产生的刺激最为显著，菌丝体中虫草素含量增加近四倍（从28.5至117 microg g(-1)），同时EPS产量增加40%（从2.6至3.7 g l(-1)）。铵添加在5至10 mmol l(-1)时对菌丝体生长有轻微的正向作用，但在较高浓度时具有负向作用。铵添加还导致培养基pH值急剧下降，这可能是由于真菌细胞对NH(3)的摄取和H(+)的释放。
向Cs-HK1菌的菌丝体培养物中添加铵可增强细胞内虫草素的积累和EPS的产生。虫草素产量的提高可能归因于氨用于核苷合成的摄取，而EPS的增加归因于用于EPS生物合成的葡萄糖摄取增加。
这对于生物活性代谢产物的生产以及理解珍贵药用真菌中的铵代谢及其与核苷生物合成的关系具有重要意义。
