Abstract
The objective of the study is to clarify the possible roles of dissolved humic substances (HS) and dissolved organic matter (DOM). The possible roles of them are (1) they can deactivate the enzyme responsible for biodegradation (2) they can act as enzymatic substrate and (3) they can sequester the pollutant and protect it from enzymatic degradation. Degradation of phenanthrene using crude fungal ligninolytic enzymes from Agrocybe sp. CU 43 was slower with dissolved HS and Dissolved Organic Matter (DOM) addition. Their enzyme activities using catechol assay were active in all conditions; therefore HS could not deactivate the enzymes. Four dissolved HS and DOM showed the capabilities to associate with phenanthrene and protect the contaminant from enzymatic degradation; consequently the phenanthrene bioavailability was decreased. The inhibitory effect of HS and DOM by competitive or linear mixed types suggest that HS and DOM could additionally be substrates for ligninolytic enzyme. Therefore, sorption and inhibitory effects of HS could be the possible mechanisms that govern enzymatic degradation rate of the pollutant in our system. Nature and extent of HS and DOM provide unique degradation potentials for aromatic organic pollutants. Some HS characteristics such as aromatic functional groups and molecular weight showed the propensity to be susceptible to sorption and enzyme degradation phenomena.