Comparison of microbial and photochemical processes and their combination for degradation of 2-aminobenzothiazole

The transformation of 2-aminobenzothiazole (ABT) was studied under various conditions: (i) a photodegradation process at a lambda of >300 nm in the presence of an Fe (III)-nitrilotriacetic acid complex (FeNTA), (ii) a biodegradation process using Rhodococcus rhodochrous OBT18 cells, and (iii) the combined processes (FeNTA plus Rhodococcus rhodochrous in the presence or absence of light). The transformation of ABT in the combined system, with or without light, was much more efficient (99% degradation after 25 h) than in the separated systems (37% photodegradation and 26% biodegradation after 125 h). No direct photolysis of ABT was observed. The main result seen is the strong positive impact of FeNTA on the photodegradation, as expected, and on the biotransformation efficiency of ABT, which was more surprising. This positive impact of FeNTA on the microbial metabolism was dependent on the FeNTA concentration. The use of UV high-performance liquid chromatography, liquid chromatography-electrospray ionization mass spectrometry, and in situ H-1 nuclear magnetic resonance provided evidence of the intermediary products and thus established transformation pathways of ABT in the different processes. These pathways were identical whether the degradation process was photo- or biotransformation. A new photoproduct was identified (40H-ABT), corresponding to a hydroxylation reaction on position 4 of the aromatic ring of ABT.