Microbiological Aspects in the Hydroxylation of Estrogens by Fusarium moniliforme1

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A strain of Fusarium moniliforme (IH4), isolated from soil, showed outstanding enzymatic abilities to hydroxylate a number of estrogens. Estrone and estradiol were transformed into the 15α-hydroxy derivatives, and estradiol 3-methyl ether was transformed into the corresponding 6β-hydroxy derivative. Δ6-Estrone was not hydroxylated. The accumulation of 15α-hydroxyestrone was influenced by the nutritional conditions of the fungus. Maximal yield was obtained when the organism grew in Czapek solution supplemented with yeast extract, although good conversion was also found in a peptone-corn molasses medium. Substitution of NO3-N in Czapek medium with NH4-N, lactalbumin hydrolysate, Casitone, or Casamino Acids resulted in limited hydroxylation of estrone. A remarkable strain specificity was demonstrated in this conversion. Of 13 strains of F. moniliforme and Gibberella fujikuroi under investigation, only 2 strains (IH4 and ATCC 9851) accumulated substantial amounts of the 15α-hydroxylated product. However, marked quantitative variations were observed which are attributable to a different ability of the organisms to degrade the steroid nucleus. Biochemical instabilities were also found through the appearance of spontaneous variants lacking steroid-hydroxylating activity. Replacement culture studies revealed that 15α-hydroxylation of estrone was dependent on the supply of external phosphate; exogenous nitrogen or energy sources were not required. Most of the enzymatic activity was confined to the mycelia. Microconidia showed a very limited hydroxylating activity, even in the presence of supplements or energy sources.

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