Biodegradation of 2,4-D and related xenobiotic compounds

Organisms capable of degrading 2,4-D and related compounds have been studied in pure and mixed cultures. Most studies have been conducted under aerobic conditions. Some of the environmental factors identified to be significant in determining biodegradation rates include pH, temperature, aeration, supplemental nutrient supplies, culture enrichment and substrate concentration range. The Monod model appears to be most applicable to xenobiotic degradation in low substrate concentration ranges, where inhibition effects are not significant. The Haldane model provides a more complete description over a broad range of substrate concentrations because it takes substrate inhibition into account. Inhibitory effects caused by biodegradation products need to be modelled in some applications. Modelling of cometabolism is necessary to describe microbial degradation at very low concentrations. Several models are examined to determine their applicability in correlating physicochemical properties to biodegradation rate constants that can be applied to either cometabolic or growth associated substrate utilization.