Decomposition of Specifically Carbon‐14‐labeled Ferulic Acid: Free and Linked into Model Humic Acid‐type Polymers

Abstract

AbstractSide chain 1‐14C, 2‐14C, and 3‐14C, O14CH3 and ring 14C‐labeled ferulic acids were synthesized and incubated with Greenfield sandy loam top soil at rates of 100 and 1,000 ppm. The loss of the specifically labeled carbons as 14CO2 over a 12‐week period ranged from 44 to 78% and averaged 64 and 68% for the 100 and 1,000 ppm additions, respectively. The smallest loss occurred from the 2‐14C (side chain) and the greatest from the 3‐14C (side chain) and the O14CH3 carbons. Losses of 14CO2 from specifically 1 and 2‐14C‐labeled acetic, and 1‐, 2‐, and 3‐14C pyruvic acids and from 14COOH‐labeled vanillic and protocatechuic acids, all of which are common metabolic products noted during the microbial decomposition of ferulic acid, averaged about 84%. After linkage into model humic acid type polymers from hydroxyphenols and toluenes by phenolase oxidative polymerization, losses of 14C ranged from 7 to 25%. Greatest losses were from the 3‐carbon of the side chain and least from the ring carbons. Losses for ring and side chain carbons after linkage into polymers from hydroxybenzoic acids varied from 3 to 7%. Losses of about 21% occurred from the O14CH3 groups. When labeled ferulic or vanillic acids were added to cultures of Stachybotrys chartarum or Hendersonula toruloidea, from 11 to 52% of the ring 14C was incorporated into the humic acid‐type phenolic polymers formed in the nutrient solutions. Only 3 to 4% of the ring carbons of veratric acid were incorporated into the “humic acid” fraction of these fungi.