Accelerating Quinoline Biodegradation and Oxidation with Endogenous Electron Donors

Abstract

Quinoline, a recalcitrant heterocyclic compound, is biodegraded by a series of reactions that begin with mono-oxygenations, which require an intracellular electron donor. Photolysis of quinoline can generate readily biodegradable products, such as oxalate, whose bio-oxidation can generate endogenous electron donors that ought to accelerate quinoline biodegradation and, ultimately, mineralization. To test this hypothesis, we compared three protocols for the biodegradation of quinoline: direct biodegradation (B), biodegradation after photolysis of 1 h (P1h+B) or 2 h (P2h+B), and biodegradation by adding oxalate commensurate to the amount generated from photolysis of 1 h (O1+B) or 2 h (O2+B). The experimental results show that P1h+B and P2h+B accelerated quinoline biodegradation by 19% and 50%, respectively, compared to B. Protocols O1+B and O2+B also gave 19% and 50% increases, respectively. During quinoline biodegradation, its first intermediate, 2-hydroxyquinoline, accumulated gradually in parallel to quinoline loss but declined once quinoline was depleted. Mono-oxygenation of 2-hydroxyquinoline competed with mono-oxygenation of quinoline, but the inhibition was relieved when extra electrons donors were added from oxalate, whether formed by UV photolysis or added exogenously. Rapid oxalate oxidation stimulated both mono-oxygenations, which accelerated the overall quinoline oxidation that provided the bulk of the electron donor.

Molecular Determination of Organic Adsorption Sites on Smectite during Fe Redox Processes Using ToF-SIMS Analysis

“…Abiotic controls without PPHA or microbial inoculum were also set up (Table S2). Finally, two bioreduced samples (HS-NAu-2 + BR and BR-NAu-2 + HS) were exposed to air to evaluate the stability of adsorbed organic materials during the abiotic Fe­(II) oxidation process, as reactive oxygen species (i.e., • OH) can be produced during Fe­(II) oxygenation to degrade organic matter. , All experiments were conducted in duplicate at 20 mL volume in 60 mL dark serum bottles in a glovebox (N 2 /H 2 97:3, except the air oxidation part).…”

Photocatalytic Material–Microbe Hybrids: Applications in Environmental Remediations

“…However, this biodegradation process could be compromised if the photocatalysis products remain refractory or inhibitory. Providing readily biodegradable co-substrates such as acetate which could act as extra electron donors and energy sources will improve the microbial metabolic activity, counteract toxicity effects, and accelerate oxygenation reactions, resulting in a great increase of the removal rate (Bai et al, 2015;Xiong et al, 2018). In PMH systems, photogenerated holes need to be scavenged, which will ensure the system will provide reductive electrons for microbial synthesis or the photoreductive degradation of target pollutants.…”

The role of oxygen and electron donors in indole biodegradation and mineralization

“…Recently, strategies for sequential/intimate coupling of UV and biodegradation have been successfully applied to speed up the biodegradation of various refractory organic compounds . 29–33 When oxygen is sufficient, the supplement of electron donors could accelerate the initial mono‐oxygenation, thereby promoting indole removal.…”

“…Recently, strategies for sequential/intimate coupling of UV and biodegradation have been successfully applied to speed up the biodegradation of various refractory organic compounds . [29][30][31][32][33] When oxygen is sufficient, the supplement of electron donors could accelerate the initial mono-oxygenation, thereby promoting indole removal. However, unlike other identifiable mono-oxygenation products for most recalcitrant compounds in aerobic biodegradation, the unstable indoxyl is only a proposed substance in all the literature, which may lead to uncertainties on mono-oxygenation.…”