Impact of different nitrogen amendments on the biodegradation of 14C-phenanthrene by endophytic fungal strains in liquid culture

Abstract

In this study, the biodegradation of phenanthrene was investigated in newly isolated endophytic fungal strains, Fusarium sp. (KTS01), Trichoderma harzianum (LAN03), Fusarium oxysporum (KTS02), Fusarium oxysporum (LAN04), and Clonostachys rosea (KTS05). This was performed under different carbon:nitrogen ratios (10:1, 20:1, and 30:1) using different nitrogen sources (urea and malt extract and ammonium nitrate) over a 30 d incubation period in both static and agitated liquid media. The kinetics of polycyclic aromatic hydrocarbons (PAH) mineralisation to CO2 (lag phases, fastest rates, and overall extents) were measured for all of the fungal strains and nutrient conditions using 14C-phenanthrene. All fungal strains were able to biodegrade 14C-phenanthrene to 14CO2 under the different nutrient amendments. However, 14C-phenanthrene mineralisation varied for most of the fungal strains in static and agitated culture conditions. Greater extents of mineralisation were found in fungal cultures (strains KTS05 and KTS01) with C:N ratio of 10:1 in both static and agitated conditions, while the fungal strains (KTS05 and LAN03) showed the greatest phenanthrene mineralisation after N source amendments, particularly with malt extract. In addition, the phenanthrene mineralisation increased with higher C:N ratios for Clonostachys rosea (KTS05) only. Consequently, the results reported here provide a promising potential for the endophytic fungal strains and the importance of nutrients amendments for the enhanced degradation of PAHs contaminated environments.