Microbial use of podzol Bh fulvic acids

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Abstract
A Trichoderma viride, a Penicillium frequentons, and an Aspergillus fumigatus were isolated from fulvic acid enrichment cultures. These and a white rot fungus, Poria subacida 17780, were tested for their ability to decompose fulvic acids (FA) in liquid cultures. All of the organisms tested were totally inhibited by the presence of FA at 1% concentration. The soil isolates brought about transformation of the FA to humic acids. In 48 h, the Poria subacida used 66% of the FA (0.05%) present as the sole source of carbon in static replacement culture, and up to 45% in 24 days in a static culture. Loss of FA was measured by photometry and confirmed by determination of the carbon content of FA precipitated as iron complex before and after attack. Phenol oxidase of the Poria subacida apparently had no role in degradation of the FA but could darken the color of a well-aerated medium through oxidative transformation of FA products.Preliminary studies with cell-free preparations of the P. subacida indicated that the breakdown is initiated by an enzyme present in particulate fraction of the cells and this activity is extended or facilitated by a factor present in the soluble fraction of the cells. FA-cleaving enzymes(s) may thus be available for use in controlled FA degradation studies aimed at characterizing soil humus.

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