Relation of chemical properties of soil humic acids to decolorization by white rot fungus–Coriolus consors

Biodegradation of soil humic acids by Streptomyces viridosporus ATCC 39115 growing in a mineral salts – glucose medium was demonstrated. This biodegradation accompanies bacterial growth and is, therefore, presumed to be a primary metabolic activity, but humic acids were not used as the sole source of carbon. This bacterial activity was enhanced when cells were shaken and within a pH range of 6.5–8.5. In further experiments, the relative abilities of S. viridosporus to mineralize [14C]melanoidin, used as synthetic humic acid, were also established. In contrast to the white rot fungus Phanerochaete chrysosporium, another microorganism exhibiting humic acid degrading activity at acidic pH, poor extracellular activities were found in culture medium of S. viridosporus, and veratryl alcohol does not result in increased humic acid degradation. In spite of some peroxidase activity measured in culture filtrates and analyzed by polyacrylamide gel electrophoresis, the humic acid degrading system of S. viridosporus, in these experimental conditions, seems to be cell associated. Key words: humic acid biodegradation, melanoidin mineralization, Streptomyces viridosporus, cell-bound humic acids.

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Comparison of some properties of soil humic acids and synthetic phenolic polymers incorporating amino derivaties

Soil Research ◽

10.1071/sr9660041 ◽

1966 ◽

Vol 4 (1) ◽

pp. 41 ◽

Cited By ~ 46

Author(s):

JN Ladd ◽

JHA Butler

Keyword(s):

Amino Acids ◽

Amino Acid ◽

Acid Hydrolysis ◽

Humic Acids ◽

Gel Filtration ◽

Quinone Imine ◽

Peptide Bonds ◽

Molecular Weights ◽

Soil Humic Acids ◽

Properties Of Soil

Twenty-three model phenolic polymers, either nitrogen-free or incorporating amino acids, peptides, or proteins, have been prepared from p-benzoquinone and catechol under mild oxidative conditions. Two lines of experimentation have demonstrated properties of soil humic acids closely similar to those of polymers incorporating proteins, but different from those of polymers incorporating amino acids: (1) fractionation of humic acids and synthetic polymers by 'Sephadex' gel filtration showed that the percentage of components of molecular weights nominally greater than 100 000 ranged from 52-76 % for eight humic acids tested, 53-59 % for benzoquinone-protein polymers (excluding polymers containing protamine), but less than 20% for all other polymers; (2) acid hydrolysis with 6M HCl resulted in a partial release of polymer nitrogen. Amino acid nitrogen in the hydrolysates accounted for 32.4-51.9 % of humic acid nitrogen, 31.2-56.3 % of the nitrogen of polymers incorporating protein, but less than 10.8% of the nitrogen of polymers incorporating individual amino acids. Experiments with model monomeric N-phenylglycine derivatives and with polymers incorporating simple peptides showed that the bond between the carbon atom of an aromatic ring and the nitrogen atom of an a-amino acid is far more stable to acid hydrolysis than peptide bonds or bonds linking amino acids in humic acids. Glycine is, however, readily released from N-phenylglycine derivatives when conditions favour their oxidation to a quinone-imine intermediate. Incorporation of proteins into phenolic polymers prevented the detection of peptide bonds by the Folin reagent.

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