Thesis for Master of Science
«Study
of the response of the enzymatic system of Phragmites australis after exposure
to an azo dye (Acid Orange 7)»
MSc.
in Biotechnology (Biochemical Engineering), IST, 2006-11-28
Supervisor:
S.
Martins-Dias
In the present work, the role of the enzymatic system of Phragmites australis, in the degradation of an azo dye, Acid-Orange 7 (AO7), was studied through the activity characterization of detoxifying (glutathione S-transferase) and antioxidant enzymes (superoxide dismutase, peroxidases, catalase, ascorbate peroxidases and dehidroascorbate peroxidase), obtained from crude extracts of roots, stems and leaves. Two different exposure conditions of P. australis to AO7, Long Term Stress and Short Term Stress, at AO7 concentrations of 130 e 700 mgl-1, were tested. A Sub-Surface Flow Constructed Wetland, planted with P. australis was used.
A strong correlation between enzymatic activity and AO7 concentration was observed, suggesting a typical behaviour, characterized by a positive activation of the antioxidant system for the moderate shock conditions (130 mgl-1), and a negative one for the stronger shock conditions (700 mgl-1), due to inhibition caused by the presence of excessive reactive oxygen species, as a consequence of the AO7 concentration increase. The exposure time did not influence significantly the system response.
In vitro assays, with a P. australis
leaves crude extract, evidenced the active role of these enzymes in AO7
degradation. The kinetic constants Km (192 mmol l-1) and vmáx
(0,318 mmol l-1 min-1) were obtained.
Keywords:
Phytoremediation,
oxidative stress, detoxification, stress response enzymes, enzimatic kinetics,
textile industry effluents