ABTS mediator enhances biotransformation of fluoranthene by Laccases from Trichoderma lixii FLU1 and Talaromyces pinophilus FLU12

Fluoranthene poses a significant environmental threat due to its persistence and toxicity. The Laccases from Trichoderma lixii FLU1 (TlFLU1L) and Talaromyces pinophilus FLU12 (TpFLU12L) are shown to act as biocatalysts for fluoranthene degradation. 3 U/mL of TlFLU1L and TpFLU12L reduced residual fluoranthene concentration to 49.5 ± 8.68 and 61.0 ± 5.66 %, while 10U/mL to 19.2 ± 5.95 and 28.7 ± 1.25 %, respectively, in 96 h. Mixing 200 μM ABTS (2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) with 3 U/mL enzyme in the reaction abolished 100 % residual fluoranthene within 48 h. TlFLU1L and TpFLU12L exhibited almost similar v_max (1.35 ± 0.02 and 1.29 ± 0.15 mg/L/h, respectively), but TlFLU1L showed a lower K_m as compared to TpFLU12L (119.2 ± 0.02 and 170.8 ± 0.15 mg/L, respectively). ABTS significantly increased v_max to 7.73 ± 0.23 and 7.97 ± 0.28 mg/L/h, and decreased K_m to 54.8 ± 0.27 and 26.6 ± 0.21 mg/L for TlFLU1L and TpFLU12L, respectively. GC-MS analysis revealed that TlFLU1L generated metabolites 9-oxo-fluorene-1-carboxylic acid, 9H-fluoren-9-one, and phthalic acid while TpFLU12L produced 9,10-phenanthrenedione and benzene-1,2,3-tricarboxylic acid. Ecotoxicity and cytotoxicity analysis of TlFLU1L and TpFLU12L degradation products in the presence of the mediator (ABTS) are found to be non-toxic towards marine bacteria (Vibrio parahaemolyticus) and HT22 cells. Thus, the study underscores the promising potential of TlFLU1L and TpFLU12L, particularly in conjunction with mediator (ABTS), for environment friendly and efficient bioremediation of fluoranthene-contaminated environments.