Soluble Microbial Product Formation in Biological Systems

The formation of soluble microbial products was evaluated in batch reactors using radiolabeled ¹⁴C-phenol and ¹⁴C-glucose. Soluble microbial products, SMP, resulted from intermediates or end products of substrate degradation and endogenous cell decomposition. On an organic carbon basis, the SMP produced after A8 hours averaged 1A.7 (±3.7) percent of the initial phenol and 3.1 (±0.4) percent of the initial glucose. The SMP were categorized as substrate utilization products, having a biodegradable and non-biodegradable fraction, and biomass associated products, which were only non-biodegradable. A model was developed based on kinetic relationships between several macroscopic compartments, which consisted of the initial substrate, cell mass, and the three SMP categories. Based on the experimental data, zero and first order kinetics were sufficient to describe the disappearance of the initial substrates and the net SMP, i.e., total SMP produced less SMP biodegraded to yield CO₂ and/or new biomass. Both phenol and glucose adhered to the same kinetic model, but the rate constants were considerably different.