| 摘要 |
1279028 Producing the antibiotic siccanin SANKYO CO Ltd 26 June 1970 [3 July 1969] 31187/70 Heading C2A The antibiotic siccanin is produced by aerobically cultivating Helminthosporium siccans in a nutrient medium wherein the pH falls during cultivation to a value below the optimum pH for the growth of the micro-organism. The optimum pH for growth is 5À0 to 6À0, this being the preferred starting pH in the process; the final pH is preferably 2À5 to 3À0. The fall in pH may be effected by incremental addition of an acid (e.g. HCl, H 2 SO 4 or HNO 3 ) throughout the cultivation; or by including in the medium a nutrient source, such as an ammonium salt of one of the said acids, which liberates an acid upon its assimilation by the micro-organism. The siccanin is isolated by collecting the mycelium and extracting it with a hydrophilic solvent, e.g. acetone. Reducing the pH during cultivation is said to cause the siccanin to be retained in the mycelium rather than migrate into the culture broth. Two comparative examples are given wherein the micro-organism is grown in a conventional manner and the pH does not fall during cultivation.
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