Use of Silica-Encapsulated Pseudomonas sp. Strain NCIB 9816-4 in Biodegradation of Novel Hydrocarbon Ring Structures Found in Hydraulic Fracturing Waters

Abstract

The most problematic hydrocarbons in hydraulic fracturing (fracking) wastewaters consist of fused, isolated, bridged, and spiro ring systems, and ring systems have been poorly studied with respect to biodegradation, prompting the testing here of six major ring structural subclasses using a well-characterized bacterium and a silica encapsulation system previously shown to enhance biodegradation. The direct biological oxygenation of spiro ring compounds was demonstrated here. These and other hydrocarbon ring compounds have previously been shown to be present in flow-back waters and waters produced from hydraulic fracturing operations. Pseudomonas sp. strain NCIB 9816-4, containing naphthalene dioxygenase, was selected for its broad substrate specificity, and it was demonstrated here to oxidize fundamental ring structures that are common in shale-derived waters but not previously investigated with this or related enzymes. Pseudomonas sp. NCIB 9816-4 was tested here in the presence of a silica encasement, a protocol that has previously been shown to protect bacteria against the extremes of salinity present in fracking wastewaters. These studies demonstrate the degradation of highly hydrophobic compounds by a silica-encapsulated model bacterium, demonstrate what it may not degrade, and contribute to knowledge of the full range of hydrocarbon ring compounds that can be oxidized using Pseudomonas sp. NCIB 9816-4.

Engineering of a silica encapsulation platform for hydrocarbon degradation using Pseudomonas sp. NCIB 9816‐4

“…Perullini et al () reported a lower E of 0.065 kPa and did not report σ f . The improvement in the mechanical properties achieved here was mainly due to the higher silica content of the gels developed as compared to the previous studies (Aukema et al, ; Dickson and Ely, ; Eleftheriou et al, ; Perullini et al, ; Reátegui et al, ) as σ f and E are strong functions of the silica density within the gel (Woignier et al, ; Woignier and Phalippou, ). This was achieved while the biodegradation activity could be sustained at high levels.…”

“…Nevertheless, silica gel bioencapsulation has been investigated as a method for deploying bacteria to remove hydrocarbons from contaminated water (Branyik et al, 1998;Khongkhaem et al, 2011;Pannier et al, 2010;Rodrigues et al, 2013) as well as for other biotechnology applications (Avnir et al, 2006;Gill and Ballesteros, 2000;Meunier et al, 2010;Nassif and Livage, 2011). Biodegradation of aromatic ring systems (Aukema et al, 2014) and complex hydrocarbon solutions (Strong et al, 2013) using silica encapsulation have also been previously studied by our group. While those studies focused on the variety of chemicals degraded by the organisms, they have not delved into the engineering challenges associated with: (i) cytocompatibility of the gel and the encapsulation process; (ii) structural integrity of the silica gel; and (iii) long term, sustained biodegradation activity of the encapsulated cells.…”

OleA Glu117 is key to condensation of two fatty-acyl coenzyme A substrates in long-chain olefin biosynthesis

“…After incubations of 1, 3, and 24 hours, reactions were quenched with an equal volume of ethyl acetate. The organic phase was extracted and 5 μL was analyzed by gas chromatography, splitting the sample between the flame ionization detector and the mass spectrometer as previously described [25]. Elution program conditions consisted of 250°C inlet temperature, 100°C start temperature, 10°C/min ramp rate, 320°C final temperature, and a 5 min hold time (total time of 27 min).…”

Silica ecosystem for synergistic biotransformation

“…Bioremediation of PAHs is shown to be feasible using Pseudomonas sp. NCIB 981613, but the process requires continuous oxygenation via mechanical aeration. Aeration can account for more than 50% of the overall energy consumption in a typical bioremediation processes14, making bioremediation economically less feasible.…”