Stabilization of Amino Sugar Units in Humic‐Type Polymers

Studies were conducted on the stabilization of amino sugar compounds against microbial degradation by the nucleophilic addition of the amino group to the aromatic nuclei of quinones. In accord with previous respirometer studies with amino acids and peptides, the presence of glucosamine or chitosan (polyglucosamine) increased O 2 uptake in reaction mixtures of phenolics undergoing enzymatic or autoxidative polymerization. Model humic acids were prepared by enzymatic or autoxidative polymerization of mixtures of phenols commonly found to occur in soil or fungal humic acids. Labeled 14 C glucosamine and chitosan were incorporated separately into these model polymers and the stabilization of the carbohydrate C against microbial attack in soil studied. For comparative purposes, peptone was also incorporated into model polymers. During a 12‐week soil incubation period 15–23% of the 14 C activity of the glucosamine model polymers was evolved as CO 2 , whereas over 70% was evolved when glucosamine was added to the soil alone or mixed with a preformed model polymer. Four to 11% of the polymers incorporating peptone decomposed during this period. During an 8‐week period, 53% of the chitosan was lost as CO 2 when added alone but only 31% of the chitosan which had been incorporated into the model humic polymer was lost. From 5–15% of the 14 C activity in the glucosamine‐phenol model polymers could be solubilized by a 24 hour, 100C, 6 N HCl hydrolysis. Residual 14 C activity was distributed among all soil humus fractions after the incubation period. Infrared spectra were obtained of the model polymers alone, and incorporating glucosamine and peptone. Significant changes in absorbance occurred depending on the functional groups incorporated.