MICROBIAL UTILIZATION OF SOIL HUMIC ACIDS

Abstract

Soil organisms capable of growth on humates were isolated by direct plating and enrichment culture techniques. A strain of Penicillium frequentans, which was selected for further studies, utilized 32% of the humates supplied in replacement-shake cultures. Elemental and spectroscopic analyses of the 'original' and 'surviving' humates showed that the fungus preferred the aromatic moiety to the non-aromatic, nitrogen-rich portion as a source of carbon.Gel filtration studies demonstrated that 69% of the humates had molecular weights between 5000 and 50,000. The fraction (13%) with molecular weight above 50,000 was degraded to the largest extent, resulting in the production of some intermediate and small-sized molecules.It was suggested that this strain of penicillium was suitable for biodegradation studies aimed at characterizing soil humic materials.