Anaerobic Oxidation of Methane Coupled to the Reduction of Different Sulfur Compounds as Electron Acceptors in Bioreactors
IHE Delft PhD Thesis Series

This research investigated new approaches to control anaerobic methane oxidation coupled to sulfate reduction (AOM-SR) and enrich anaerobic methanotrophs (ANME) and sulfate reducing bacteria (SRB) with the purpose of designing a suitable bioreactor for AOM-SR at ambient pressure and temperature. The current knowledge about AOM and the microorganisms involved in AOM are discussed. The effect of different substrates and pressures was investigated on the ANME and SRB community adapted to the shallow marine Lake Grevelingen, the Netherlands. Further, microorganisms from the Alpha Mound (Spain) deep sediment were enriched with methane gas as substrate in biotrickling filters (BTF) at ambient conditions for 147-230 days of operation. The effect of alternative sulfur compounds (sulfate, thiosulfate and elemental sulfur) were studied and the microbial community was characterized. The highest AOM and sulfate reduction rates were obtained in the BTF fed with thiosulfate as the electron acceptor (~0.4 mmol l-1 day-1), but the highest number of ANME was visualized in the sulfate fed BTF (ANME-2 43% of the total visualized archaea). A BTF was proposed as a suitable bioreactor for the enrichment of ANME and SRB at ambient pressure and temperature which could be potentially used for future biotechnological applications.

1. General Introduction and Thesis Outline
2. Physiology and Distribution of Anaerobic oxidation of methane (AOM) by Archaeal Methanotrophs
3. Microbial Sulfate Reducing Activities in Anoxic Sediment from Marine Lake Grevelingen
4. Pressure Sensitivity on an ANME-3 Predominant Anaerobic Methane Oxidizing Community from Coastal Marine Grevelingen
5. Ananerobic Oxidation of Methane Coupled to Thiosulphate Reduction in a Biotrickling Filter
6. Enrichment of Anaerobic Methanotrophs in Biotrickling filters using Different Sulfur Compounds as Electron Acceptors
7. General Discussion and Future Perspectives

Chiara Cassarini was born in 1987 in Bologna, Italy. She completed her bachelor (BSc) in 2010 in Industrial Chemistry at the University of Bologna (Italy) and obtained her MSc degree in Geochemistry at Utrecht University (the Netherlands). She collaborated closely with the Deltares Company in the Netherlands and with the department of Isotope Biogeochemistry in Leipzig (UFZ) Germany where she used compound-specific stable isotope analysis (CSIA) to investigate the degradation of chlorinated compounds in an industrial contaminated site. Simultaneously, during her MSc studies, she participated in a research cruise on the North Sea to investigate ocean acidification. Chiara got admitted into the Erasmus Mundus Joint Doctorate Program on Environmental Technologies for Contaminated Solids, Soils and Sediment (ETeCoS3). She started as a PhD fellow at UNESCO-IHE (Delft, the Netherlands) in 2013. Within the framework of her PhD studies, she investigated how various sulfur compounds, as electron acceptors, impact the anaerobic oxidation of methane in packed bed systems.

Chiara has started a Post-Doc in anaerobic biotechnology and process bioengineering at the National University of Ireland Galway, the research is focused on new environmental technologies designed to produce biofuel from waste.