Customized ammonia tolerant methano-genic inocula to alleviate ammonia toxicity in anaerobic digesters

Anaerobic digestion (AD) is a popular organic waste management technology where the organic matters are degraded into biogas (mainly CH4 and CO2) and digestate under oxygen-free conditions. While the ammonia inhibition limits the AD process of N-rich organic waste, thus more efforts are required to maximize methane production.

This Ph.D. project developed some biological strategies to recover methane production from organic waste at high ammonia stress and explored microbial syntrophic networks as well as other functionalities determining ammonia-stress resistance.
Firstly, the acclimatization of the microbial community in continuous stirring tank reactors (CSTR) contributed to the stable methane production at high ammonia levels. Secondly, deep insight into the acclimatized microbial composition grown on different single carbon sources expanded our knowledge of the mechanism determining microbial resistance to ammonia. Then, to increase methane production, the bioaugmentation approach was applied in mesophilic CSTRs under extremely high ammonia levels. The metagenomics analysis pinpointed the social network between key microbes triggered by the bioaugmented microorganisms. Last, the ammonia tolerant microorganism preserved in the agar-gel at room temperature was recognized as an efficient long-term preservation approach.

These research findings broadened our understanding of microbial interaction and provided practical guidance for the AD process optimization.