Biodegradation of fluorinated environmental pollutants under aerobic conditions

PhD ceremony: mr. S.A. Hasan, 14.45 uur, Academiegebouw, Broerstraat 5, Groningen

Thesis: Biodegradation of fluorinated environmental pollutants under aerobic conditions

Promotor(s): prof. D.B. Janssen

Faculty: Mathematics and Natural Sciences

Contamination of air, water and soil by a large-scale synthesis of xenobiotic compounds poses harmful effects on different biota, and disruption of biogeochemical cycling. Biological pollution control methods have been gaining importance for the removal of toxic compounds from the environment and waste stream. Fundamental to these biotreatment processes are the biochemical activities of microorganisms upon which the degradation of organic pollutants depends. Microorganisms are able to decompose a wide range of organic substances, both compounds of natural and chemicals of anthropogenic origin. Due to their unique properties, fluoroorganics are of key importance for synthesis of bioactive pharmaceutical and agrochemical compounds and for electronic applications. The introduction of fluorinated agents in the environment due to human activity poses a challenge to microbial strains for the mineralization of these compounds. To study the degradation pathway of fluorinated compounds 4-fluorocinnamic acid, 4-fluorophenol, 2-fluorophenol and trifluoroacetophenone were selected as model compounds. Arthrobacter sp G1 and Ralstonia sp. H1 completely mineralize 4-fluorocinnamic acid and release fluoride. A monooxygenase and flavin-reductase of Arthrobacter sp. IF1 together catalyze NADH-dependent hydroxylation and dehalogenation of para-substituted phenols. A Rhodococcus sp. FP1 degrades 2-fluorophenol by hydroxylation of the aromatic ring to form 3-fluorocatechol. For the degradation of trifluoroacetophenone a Gordonia sp. strain SH2 was isolated from the soil contaminated with pesticide, herbicides and other toxic compounds. Strain SH2 catalyzes a range of cyclic and aromatic ketones by NADPH-dependent Baeyer-Villiger monooxygenase (BVMO). The induced BVMO is also capable of sulfur oxidations and exhibits a good enantioselectivity (ee ≥ 97%) with selected aromatic sulfides.