Microbial transformation of lucanthone by growing cultures, washed mycelia and non-germinating spores of fungi from the Aspergillus group.

Whole broth cultures, washed mycelia and non-germinating spores of 13 aspergilli scored from among 91 moulds isolated from soil and air transformed lucanthone (I) into three to five products with increased polarity. Biotransformations brought about by actively growing cultures were also performed by washed mycelia and non-germinating spores of the same strains. Lucanthone (I) was oxidized by growing cultures, washed mycelia and spore suspensions of an Aspergillus species (no. 2) into: hycanthone (II) as the main product, its aldehyde analogue (III) and its carboxylic acid derivative (IV). The pathway of lucanthone (I) oxidation by this strain involved hydroxylation of the 4-methyl group (to give hycanthone, II) followed by dehydrogenation of the resulting primary alcohol (to give the aldehyde, III). The aldehyde III was finally slowly oxidized to the corresponding carboxylic acid analogue IV. Evidence is presented to show that mycelial and spore enzymes effecting these oxidative reactions are intracellular and non-inducible in nature. Spore-mediated transformations were found not to require a source of energy and could be conducted in distilled water over a wide range of incubation temperature (from 4 to 37 degrees C). Use of the spores in successive transformations did not affect lucanthone (I) hydroxylation into hycanthone (II) or the dehydrogenation of the latter into the aldehyde analogue (III) but the ability of the spores to oxidize the aldehyde (III) to the carboxylic acid (IV) was lost.