DEGRADATION OF MELANOIDINS BY SOIL MICROORGANISMS UNDER LABORATORY CONDITIONS

Abstract

Synthetic melanoidins, unlabeled and U–14C labeled, mixed with sand, inoculated with a soil suspension and incubated in Warburg vessels for 30 d, decomposed slowly. Reactants (amino acids, sugars and NH4 salts) involved in melanoidin formation had no influence on rate of degradation, nor did the pH at which the melanoidins were synthesized. However, temperature of synthesis affected the rate; an increase led to a decrease in biodegradability paralleled by both increase in C:N ratio and unsaturation. At lower temperatures species of Penicillium, Cladosporium and Paecilomyces were the dominant fungi degrading the polymers, while at higher temperatures only Penicillium species were present. Key words: Melanoidins, decomposition by soil microbes