Biodegradation kinetics of chlorophenols in immobilized-cell reactors using a white-rot fungus on wood chips

This research investigated the ability of wood-chip reactors seeded with a white-rot fungus (Phanerochaete chrysosporium) to degrade hazardous substances (4-chlorophenol [4-CP] and 2,4-dichlorophenol [2,4-DCP]). Batch-reactor tests were conducted using 4-CP as a model compound to evaluate the effect of carbon and nitrogen deficiencies on the ability of white-rot fungus immobilized on wood chips to degrade 4-CP. The white-rot fungus degraded 4-CP (71.1 to 83.0%) under all tested conditions including the non-glucose and non-nitrogen conditions. However, there are differences in the degradation percentager of 4-CP using the different growing conditions. The degradation of 4-CP occurs to the greatest extent in the non-glucose/with-nitrogen condition (15.38 ppm/h·g of specific biodegradation rate). Continuous-flow packed-bed reactor tests are conducted using 2,4-DCP as a model compound to evaluate the inhibition effect of 2,4-DCP on the biodegradation enzymes in wood-chip reactor systems, and the inhibition effects seem to be present. The inhibition kinetics of 2,4-DCP are successfully modeled with the mass-balance equation of plug-flow reactors and a substrate-inhibition equation for the reaction rate, yielding an inhibition constant,$K_{i}$, of 69.8 ppm and a maximum 2,4-DCP concentration,$[S]_{{\rm max}}$, of 48.9 ppm at the highest reaction rate. The importance of these results is that the substrate-inhibition model can be used to explain the inhibition effect of 2,4-DCP on the biodegradation enzymes in this wood-chip reactor system. This study points to the potential of continuous-flow reactors using wood chips as a carbon source to degrade toxic chemicals with high-degradation efficiency.