Biosorption and biodegradation of polycyclic aromatic hydrocarbons in aqueous solutions by a consortium of white-rot fungi.

ABSTRACT

Bioremediation is a popular approach used to abate polycyclic aromatic hydrocarbons (PAHs) in the environment. A consortium of white-rot fungi (CW-1) isolated from wood pieces was used for studying their potential of bioremediation of PAHs. Biosorption and biodegradation of PAHs by live and heat-killed white-rot fungi (CW-1) were investigated to elucidate the bio-dissipation mechanisms of PAHs. Sorption isotherms of naphthalene, acenaphthene, fluorene, phenanthrene and pyrene to heat-killed fungal biomass were linear and non-competitive, indicating the primary mechanism of biosorption to be by partition. The carbon-normalized partition coefficients (K(oc)) were linearly correlated with octanol-water partition coefficients (K(ow)), i.e., log K(oc)=1.13 log K(ow)-0.84 (n=5, r(2)=0.996). Biosorption and biodegradation of phenanthrene and pyrene by live white-rot fungi were quantified. In 1 week, the removal efficiency of phenanthrene (70-80%) and pyrene (90%) by live fungi from aqueous solution were comparable to those by heat-killed fungi. However, approximately 40-65% of phenanthrene and 60-85% of pyrene were still stored in organismal bodies. Biosorption might restrict biodegradation while nutrient limitation and presence of a PAH mixture might stimulate biodegradation. The apparent partition coefficients (K(d)(*)) in live fungal systems and the K(d) of heat-killed fungi without biodegradation were compared, and then the K(d)(*)/K(d) ratios were employed to illustrate the relative contributions of biosorption and biodegradation under different nutrient conditions.