The role of paraffin oil on the interaction between denitrifying anaerobic methane oxidation and Anammox processes

Abstract

Methane is sparingly soluble in water, resulting in a slow reaction rate in the denitrifying anaerobic methane oxidation (DAMO) process. The slow rate limits the feasibility of research to examine the interaction between the DAMO and the anaerobic ammonium oxidation (Anammox) process. In this study, optimized 5 % (v/v) paraffin oil was added as a second liquid phase to improve methane solubility in a reactor containing DAMO and Anammox microbes. After just addition, methane solubility was found to increase by 25 % and DAMO activity was enhanced. After a 100-day cultivation, the paraffin reactor showed almost two times higher consumption rates of NO3 (-) (0.2268 mmol/day) and NH4 (+) (0.1403 mmol/day), compared to the control reactor without paraffin oil. The microbes tended to distribute in the oil-water interface. The quantitative (q) PCR result showed the abundance of gene copies of DAMO archaea, DAMO bacteria, and Anammox bacteria in the paraffin reactor were higher than those in the control reactor after 1 month. Fluorescence in situ hybridization revealed that the percentages of the three microbes were 55.5 and 77.6 % in the control and paraffin reactors after 100 days, respectively. A simple model of mass balance was developed to describe the interactions between DAMO and Anammox microbes and validate the activity results. A mechanism was proposed to describe the possible way that paraffin oil enhanced DAMO activity. It is quite clear that paraffin oil enhances not only DAMO activity but also Anammox activity via the interaction between them; both NO3 (-) and NH4 (+) consumption rates were about two times those of the control.

Comparative performance evaluation of conventional and two‐phase hydrophobic stirred tank reactors for methane abatement: Mass transfer and biological considerations

“…1). A similar growth pattern has been reported in previous studies for different NAPs, where bacteria were able to accumulate in the aqueous-NAP interphase and grow inside NAPs forming aggregates (Fu et al, 2015;Han et al, 2009b;Yamashita et al, 2007). Moreover, MacLeod and Daugulis (2005) observed that certain hydrophobic bacteria formed aggregates in the aqueous phase instead of inside the NAP.…”

Biomimetic Regulation of Microbially Induced Calcium Carbonate Precipitation Involving Immobilization of Sporasarcina pasteurii by Sodium Alginate

“…Prior to microscopy, the microorganisms immobilized in gels were fixed with 4% (w/v) paraformaldehyde at 4 °C for 2 h and then washed with 1× phosphate-buffered saline (PBS). The microorganism immobilization system was stained with 4′,6-diamidino-2-phenylindole (DAPI) and cut into slices with a microtome (Leica CM1950, Wetzlar, Germany) . The slice was then transferred onto the well of a microscope slide just before observation.…”

“…The microorganism immobilization system was stained with 4′,6-diamidino-2-phenylindole (DAPI) and cut into slices with a microtome (Leica CM1950, Wetzlar, Germany). 31 The slice was then transferred onto the well of a microscope slide just before observation. A phase contrast microscope (Olympus IX81) was used to analyze the gel structures in the slices.…”

Ammonium level induces high purity propionate production in mixed culture glucose fermentation

“…Ammonium was analyzed using a water quality autoanalyzer (ThermoFisher, Aquakem 200, Finland) based on the hydrazine reduction method, which was described in Fu's study. 23 The produced biogas was recorded daily by a gas meter. 24 The content of hydrogen in the headspace was determined with a Gas Chromatograph (Lunan model SP7890, China) equipped with a thermal conductivity detector and a 1.5 m stainless steel column packed with 5Å molecular sieve.…”