George Cheng

Acetogens are responsible for one of the four steps in the biogas process, acetogenesis. These microbes are capable of fixing carbon via the Wood-Ljungdahl pathway (WLP), which is highly conserved across Bacteria and Archaea. An important distinction in the definition for acetogens, that is acetyl-CoA being produced from two molecules of CO2. Key enzymes from the WLP, i.e., formyltetrahydrofolate synthetase (FTHFS) and carbon monoxide dehydrogenase/acetyl-CoA synthetase (CODH/ACS), were used to screen through metagenomic assembled genomes (MAGs). To further corroborate the presence of the WLP, the CODH/ACS is required to also be present. However, there is no similar dedicated databases for acetogenic CODH/ACS.

The systems that have been explored so far include thermophilic high-ammonia biogas reactors and syngas trickle bed reactor. The thermophilic high-ammonia biogas reactors operated with slaughter-house waste and food waste or waste water. Within these reactors, several MAGs revealed the presence of FTHFS except many of them missing CODH/ACS; or rather the MAGs did not match in similarity to already known CODH/ACS genes. There could be two potential explanations; first being that the MAGs do not possess the CODH/ACS complex and utilize a different pathway, i.e., the glycine cleavage system pathway. Second, the genes for the CODH/ACS complex within the genomes are different from the ones that are already established. The goal now is to determine if there is a hypothetical protein that is functioning the same as the CODH/ACS or if these MAGs utilize and alternative pathway to WLP.

Genetics, cell biology and microbiology- BI1278 
(Autumn 2021, 2022)

Microbiology- BI1337 
(Spring 2021, 2022)

PhD in Biology with specialisation in biotechnology
Swedish University of Agricultural Sciences, Uppsala, Sweden 
(January 2020- September 2024)

MSc in Biology- Ecology and Conservation
Uppsala University, Uppsala, Sweden 
(August 2017- June 2019)

BSc in Liberal Arts and Sciences- Integrative Biology
University of Illinois at Urbana-Champaign, Illinois, USA 
(August 2011- June 2015)

For more publication, please visit my Google Scholar Page here.

Cheng, G., Gabler, F., Pizzul, L., Olsson, H., Nordberg, Å. & Schnürer, A. (2022). Microbial community development during syngas methanation in a trickle bed reactor with various nutrient sources. Applied Microbiology and Biotechnology, 106 (13), 5317–5333. https://doi.org/10.1007/s00253-022-12035-5

Cheng, G., Westerholm, M. & Schnürer, A. (2024). Complete genome sequence of Citroniella saccharovorans DSM 29873, isolated from human fecal sample. Microbiology Resource Announcements, 13 (4), e0001524. https://doi.org/10.1128/mra.00015-24

Cheng, G.B., Bongcam-Rudloff, E. & Schnürer, A. (2025). Metagenomic Exploration Uncovers Several Novel ‘Candidatus’ Species Involved in Acetate Metabolism in High-Ammonia Thermophilic Biogas Processes. Microbial Biotechnology, 18 (3), e70133. https://doi.org/10.1111/1751-7915.70133

Cheng, G., Schnürer, A. & Westerholm, M. (2025). Microaceticoccus formicicus gen. nov., sp. nov., an ammonia-tolerant formate-utilizing bacterium originating from a biogas process. International Journal of Systematic and Evolutionary Microbiology, 75 (5), 006773. https://doi.org/10.1099/ijsem.0.006773