Generating 2-hydroxyl quinoline from quinoline through a single mono-oxygenation by Delftia lacustris

Quinoline and its derivatives are nitrogenous heterocyclic compounds with biological and pharmaceutical activities. 2-hydroxyl quinoline (2-HQ), a representative derivative, currently is synthesized through chemical methods that have high energy consumption and secondary-pollution risks. In this work, 2-HQ was generated from quinoline by a strain of Delftia lacustris that was isolated from quinoline-acclimated sludge. D. lacustris carried out only one step mono-oxygenation of quinoline, which transformed it into 2-HQ. 2-HQ was not further transformed unless quinoline disappeared completely. When succinate was added as an exogenous electron donor, quinoline transformation was significantly accelerated: the rate was increased by 89 % and 120 % with 0.1-mM and 0.2-mM succinate added, respectively, which supports that 2-HQ was product of quinoline mono-oxygenation requiring an intracellular electron donor. The produced 2-HQ corresponded to a standard sample of 2-HQ according to Fourier Transform Infrared and Nuclear Magnetic Resonance analyses, and the purity of the 2-HQ reached ∼80 % when inorganic salts were removed from the medium. Genomic and transcriptomic analyses confirmed the presence and expression of FAD-dependent mono-oxygenase and FMNH2-dependent alkanesulfonate monooxygenase in D. lacustris. As the economic value of 2-HQ is more than five-thousand-fold higher than quinoline, these results open the door for a promising new path for green biosynthesis that also is cleaner way to produce 2-HQ.