Microbiological surveillance of biogas plants : focusing on the acetogenic community

Abstract: Biogas process has great potential for reducing the current dependence on fossil fuels and for climate mitigation and sustainable development. In this process organic matter is decomposed under anerobic conditions by microorganisms to form biogas and a nutrient rich biofertiliser. For adequate use of the resources invested in commercial biogas production, constant monitoring and optimisation are extremely important. The biogas microbiome has been thoroughly studied, but remains a black box in terms of the microbe identity/diversity and functions/interactions in biogas production. Among known bacterial communities, acetogenic bacteria play a critical imperative role in the biogas process, so close monitoring or surveillance of the acetogenic community is important to ensure process stability and productivity. This thesis presents a new microbiological surveillance strategy targeting the acetogenic community in biogas reactors and describes the underlying theory, tools and application. In the strategy, a database (AcetoBase) and a bioinformatics analysis pipeline (AcetoScan), developed within this thesis, are employed for surveillance of acetogenic communities in laboratory- and industrial-scale biogas facilities. Meticulous comparison of the surveillance strategy with conventional methods demonstrated its superiority in envisioning acetogenic community structure and dynamics. Acetogenic community surveillance using the strategy showed that acetogenic communities in biogas reactors are substrate-specific, diverse and dynamic. The dynamic response of acetogenic communities imparts strength in resisting disturbance and potential to recover post-disturbance. Future use of the acetogenic community surveillance strategy can greatly improve understanding of the acetogenic communities and their utilization for biogas process stability.