Metabolism of Methoxylated Aromatic Compounds by Soil Fungi

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Abstract
The metabolism of methoxylated aromatic compounds by the soil fungi Haplographium sp.. Hormodendrum sp. and Penlcillium sp., was investigated. A study of rates of decomposition of monomethoxybenzoic acids by Hormodendrum sp. revealed that these acids are most rapidly attacked in the order para (p), meta (m) and ortho (o). In respiration studies with all 3 fungi, the p form was again found to be metabolized most rapidly. In the initial stage of attack the methoxyl group is replaced by a hydroxyl group. Penlcillium sp. also formed p-methoxyphenol from p-methoxybenzoic acid. A study of the rates of metabolism of mono-hydroxybenzoic acids revealed that these acids are attacked in the same order as the monomethoxybenzoic acids. p-Hydroxybenzoic acid formed from p-methoxybenzoic acid is further metabolized to protocatechnic acid by Hormodendrum sp. and Penicillium sp. When veratric acid (3:4-dimethoxybenzoic acid) is incubated with Hormodendrum sp. and Penicillium sp.. the methoxyl group in the p position is replaced by a hydroxyl group to give vanillic acid. All 3 fungi formed 2 unidentified phenolic compounds from 2:4-dimethoxybenzoic acid. The possible significance of the results in the decomposition of lignin in soil is discussed.