Anaerobic ethylene glycol degradation by microorganisms in poplar and willow rhizospheres

Abstract

Although aerobic degradation of ethylene glycol is well documented, only anaerobic biodegradation via methanogenesis or fermentation has been clearly shown. Enhanced ethylene glycol degradation has been demonstrated by microorganisms in the rhizosphere of shallow-rooted plants such as alfalfa and grasses where conditions may be aerobic, but has not been demonstrated in the deeper rhizosphere of poplar or willow trees where conditions are more likely to be anaerobic. This study evaluated ethylene glycol degradation under nitrate-, and sulphate-reducing conditions by microorganisms from the rhizosphere of poplar and willow trees planted in the path of a groundwater plume containing up to 1.9 mol l(-1) (120 g l(-1)) ethylene glycol and, the effect of fertilizer addition when nitrate or sulphate was provided as a terminal electron acceptor (TEA). Microorganisms in these rhizosphere soils degraded ethylene glycol using nitrate or sulphate as TEAs at close to the theoretical stoichiometric amounts required for mineralization. Although the added nitrate or sulphate was primarily used as TEA, TEAs naturally present in the soil or CO(2) produced from ethylene glycol degradation were also used, demonstrating multiple TEA usage. Anaerobic degradation produced acetaldehyde, less acetic acid, and more ethanol than under aerobic conditions. Although aerobic degradation rates were faster, close to 100% disappearance was eventually achieved anaerobically. Degradation rates under nitrate-reducing conditions were enhanced upon fertilizer addition to achieve rates similar to aerobic degradation with up to 19.3 mmol (1.20 g) of ethylene glycol degradation l(-1) day(-1) in poplar soils. This is the first study to demonstrate that microorganisms in the rhizosphere of deep rooted trees like willow and poplar can anaerobically degrade ethylene glycol. Since anaerobic biodegradation may significantly contribute to the phytoremediation of ethylene glycol in the deeper subsurface, the need for "pump and treat" or an aerobic treatment would be eliminated, hence reducing the cost of treatment.

Facile preparation and enhanced photocatalytic H2-production activity of Cu(OH)2 cluster modified TiO2

“…In comparison, the utilization of organic pollutants or industrial waste as sacrificial reagents, followed by decomposing them into environmentally friendly products, has been identified as a clean and economical method. 30,31 For example, ethylene glycol is produced in large amounts as industrial and civil waste, [32][33][34] and has been proven to be an effective electron donor for photocatalytic hydrogen generation. 35 On the other hand, for effective H 2 -production, noble metals, such as Pt, 30 Au 31 and Pd, 36 must be used in most photocatalytic systems as a co-catalyst loaded onto the surface of TiO 2 to promote the separation and transfer of charge carriers from the TiO 2 to the loaded noble metals where H + is reduced to hydrogen molecules.…”

“…Photocatalytic H 2 -production activity on various samples was evaluated under UV-LED irradiation using ethylene glycerol as a scavenger. [32][33][34][35] Control experiments indicated that no appreciable hydrogen production was detected in the absence of either irradiation or photocatalyst, suggesting that hydrogen was produced by photocatalytic reactions on photocatalyst. Fig.…”

Poplar

“…Two mechanisms for removal of ethylene glycol (microbial degradation in the rhizosphere and uptake by the trees through evapotranspiration) have been identified [34,35]. Based on these results, it is very probable that similar mechanisms can be effective for removal of other organic compounds.…”

Possibility of teaching Bacillus subtilis ethylene glycol utilization

“…3 Another study documented the anaerobic biodegradation of ethylene glycol by microbes in the rhizosphere of poplar and willow trees with complete conversion of ethylene glycol using nitrate and sulphate as terminal electron acceptors. 4 Psychotropic bacterium such as Pseudomonas fluorescens has also been reported to degrade ethylene glycol with the substrate inducing the expression of ethylene glycol shock and acclimation proteins. 5 Besides degradation of ethylene glycol, there have also been studies on the biosynthesis of the molecule.…”