MOLECULAR-WEIGHT DISTRIBUTION OF SOLUBLE MICROBIAL PRODUCTS IN BIOLOGICAL-SYSTEMS

The molecular weight, MW, distribution of soluble microbial products, SMP, was examined. Phenol, an inhibitory substrate, and glucose, a non -inhibitory substrate, were degraded using acclimated cultures of bact eria. Three distinct regions were found to exist, Region I: Original s ubstrate present, Region II: Biodegradable SMP present, and Region III : Endogenous respiration. Phenol degradation resulted in more SMP than glucose, about 25 percent versus 3 percent as residual SMP at the end of Region I, and 3 percent versus I percent at the end of Region II, respectively. In Region III, the production of SMP due to endogenous d ecay, SMP(E), was proportional to the rate of cell degradation. The ra te coefficient for SMP(E) production for cells grown on phenol was hig her than for glucose, 0.005 mg SMP(E) per mg cell carbon per day for p henol versus 0.002 mg per mg per day for glucose. Although differences existed in the magnitude of SMP produced, the MW distributions for ph enol and glucose were similar in each region. While in Region I most o f the SMP consisted of the lowest MW (<1 K daltons) compounds, 90 perc ent for phenol and 75 percent for glucose, at the end of Region II onl y 41 percent of the SMP for phenol and 56 percent for glucose were in the <1 K fraction. Finally, for endogenous decay products, 48 and 50 p ercent of the SMPE were in the highest MW fraction >100 K. Copyright ( C) 1996 IAWQ.