Roles of n-hexadecane in the degradation of dibenzofuran by a biosurfactant-producing bacterium Rhodococcus sp.

Abstract

The hydrophobic nature of dioxins is a major obstacle to their bioremediation. The present study attempted to improve the bioaccessibility of dioxins in two-phase partitioning bioreactors and activated sludge reactors. Dibenzofuran and n-hexadecane were used as model compounds for dioxins and non-aqueous phase liquids (NAPLs), respectively. First, biosurfactants produced by dioxin-degrading Rhodococcus sp. strain p52 were analyzed. Then, the role of n-hexadecane during the biodegradation of dibenzofuran was evaluated. The results showed that high NAPL ratios (n-hexadecane ≥40 g/L) in the two liquid-phase systems favored dibenzofuran removal, while the cell surface of strain p52 became extremely hydrophobic (>97%), which promoted its adhesion to NAPLs and subsequent transport of dibenzofuran from NAPL to the cells. In addition, a bioaugmented activated sludge reactor with n-hexadecane as the supplemented carbon source could not only facilitate the aerobic granular sludge formation but also improve dibenzofuran removal and the activated sludge settling properties. Simultaneously, conjugative transfer of catabolic plasmids was promoted. This study demonstrated the potential application of strain p52 with NAPLs for the bioremediation of dioxins.