Anaerobic methanethiol degradation and methanogenic community analysis in an alkaline (pH 10) biological process for liquefied petroleum gas desulfurization

Abstract

Anaerobic methanethiol (MT) degradation by mesophilic (30 degrees C) alkaliphilic (pH 10) communities was studied in a lab-scale Upflow Anaerobic Sludge Bed (UASB) reactor inoculated with a mixture of sediments from the Wadden Sea (The Netherlands), Soap Lake (Central Washington), and Russian soda lakes. MT degradation started after 32 days of incubation. During the first 252 days, complete degradation was achieved till a volumetric loading rate of 7.5 mmol MT/L/day, and sulfide, methane, and carbon dioxide were the main reaction products. Temporary inhibition of MT degradation occurred after MT peak loads and in the presence of dimethyl disulfide (DMDS), which is the autooxidation product of MT. From day 252 onwards, methanol was dosed to the reactor as co-substrate at a loading rate of 3-6 mmol/L/day to stimulate growth of methylotrophic methanogens. Methanol was completely degraded and also a complete MT degradation was achieved till a volumetric loading rate of 13 mmol MT/L/day (0.77 mmol MT/gVSS/day). However, from day 354 till the end of the experimental run (day 365), acetate was formed and MT was not completely degraded anymore, indicating that methanol-degrading homoacetogenic bacteria had partially outcompeted the methanogenic MT-degrading archea. The archeal community in the reactor sludge was analyzed by DGGE and sequencing of 16S rRNA genes. The methanogenic archea responsible for the degradation of MT in the reactor were related to Methanolobus oregonensis. A pure culture, named strain SODA, was obtained by serial dilutions in medium containing both trimethyl amine and dimethyl sulfide (DMS). Strain SODA degraded MT, DMS, trimethyl amine, and methanol. Flow sheet simulations revealed that for sufficient MT removal from liquefied petroleum gas, the extraction and biological degradation process should be operated above pH 9.

Molecular diversity of methanogens and identification of Methanolobus sp. as active methylotrophic Archaea in Lonar crater lake sediments

“…The interesting possibility of niche differentiation among methylotrophic methanogens due to competition for C 1 substrates in the extreme Lonar Lake environment needs further exploration. 16S rRNA gene sequences related to M. oregonensis have been retrieved by PCR-DGGE fingerprint analysis of methanethiol (MT) degrading communities in a UASB reactor (pH-10) inoculated with sediments from the Wadden Sea (Netherlands), Soap Lake (USA), and Russian soda lakes (van Leerdam et al, 2008). Methanolobus-related phylotypes in the Lonar Lake environment could be dependent on methanol and other C 1 substrates that are derived from the decomposition of cyanobacterial mats that extend across surface layers of the water column (Surakasi et al, 2010) and/or dead plant matter (Warneke et al, 1999).…”

Anaerobic digestion of the microalga Spirulina at extreme alkaline conditions: biogas production, metagenome, and metatranscriptome

“…Haloalkaline microorganisms have also been proposed to be applied in the production of biofuels such as hydrogen and ethanol (Zhao et al, 2014 ). Van Leerdam et al ( 2008 ) showed that it was possible to use a haloalkaline consortium to produce biogas under controlled conditions. The ability of haloalkaline bacteria and archaea to live in alkaline environments could be exploited to produce biogas rich in methane.…”

Biodegradation Potential of Halo(alkali)philic Prokaryotes

“…On the other hand, the potential to convert methane thiol and dimethyl sulfide to sulfide is shown for the moderately halophilic methanogen Methanohalophilus, but without any detailed study on salt influence of the process (Ni and Boone, Downloaded by [Stanford University Libraries] at 04:43 03 October 2012 1993). Recently, the same potential has been demonstrated for haloalkaline conditions in a bioreactor inoculated with the soda lake sediments containing Methanolobus taylorii as a dominant organism (van Leerdam et al, 2008a;van Leerdam et al, 2008b).…”