Buan Lab

Redox biochemistry and metabolic engineering

Methanosarcina

Research

Our team studies energy conservation by methanoarchaea, unique microbes that grow by producing methane gas. We use a wide variety of techniques from biochemistry, genetics, physiology, synthetic biology, and modeling, to understand how carbon and electrons flow through cells to produce new progeny, methane, and other molecules. Our work is applicable to metabolic engineering of archaea, bacteria, and plants for applications in bioenergy, sustainable biofuel, and agriculture.

Accelerating bioenergy production 

Biomethane is a clean-burning fuel that can be used for heat, electricity, transportation, and aviation fuel. It is produced through anaerobic digestion, which is a keystone technology for a sustainable, circular bioeconomy. Biomethane is made by unique methanoarchaea microbes that grow by synthesizing methane in anaerobic environments. Methanoarchaea can be grown at industrial scale and have a 98% substrate conversion efficiency, far surpassing ethanol-producing yeast or bacteria. They have several favorable characteristics for industrial-scale implementation. Methanoarchaea grow using acetate or C1 compounds (CO2, methanol, methylamines, methylsulfides, CO) as substrates for growth, which are among the least expensive non-food feedstocks and thus methanoarchaea do not compete with human and animal nutrition. Methanoarchaea can fix nitrogen to ammonium, and a byproduct of biomethane production is crop  fertilizer. They can also withstand temperatures and pressures in the deep subsurface or in industrial bioreactors, which is a prohibitive environment for many organisms. 

The Buan Lab is using synthetic biology to manipulate metabolic efficiency in these organisms. Engineered methanoarchaea have potential to increase the rate of waste biomass processing, resulting in higher yield of biomethane over shorter time periods, thus decreasing feedstock input and reducing infrastructure needs while producing clean water and fertilizer as byproducts. Methanoarchaea can also donate and accept energy from electrodes, raising the possibility of coupling solar, wind, or nuclear to biomethane as a storable fuel supply. In addition, the Buan Lab, in collaboration with UNL colleagues, have isolated a novel organism, Methanobacterium nebraskense, which can grow on solid natural and synthetic carbonate minerals, further expanding the list of substrates for industrial biomethane production and increasing the portfolio of methanoarchaea traits that may be engineered for bioeconomy applications. 

Engineering methanoarchaea to produce renewable isoprene and terpenes

Methanoarchaea can be engineered to produce isoprene, the main component of synthetic rubber, and it can be easily converted to gasoline or aviation fuel. The Buan Lab has observed up to 5% substrate conversion efficiency from methanol to isoprene using engineered methanoarchaea. Engineered methanoarchaea have been demonstrated to synthesize isoprene from municipal waste solids. Current research is ongoing to optimize isoprene production and to expand the repertoire of terpene-synthesizing methanoarchaea for fuel and chemical precursor synthesis.

Use of an archaeal antioxidant to increase crop growth and microbial fermentation

Methanoarchaea are some of the most metabolically efficient organisms known, far more than yeast, bacteria, or plants. A key to this efficiency is synthesis of 2-mercaptoethane sulfonate, CoM. CoM is a small, nontoxic, sulfur-containing molecule that accepts and donates electrons and carbon atoms in methanoarchaea. In collaboration with UNL colleagues, the Buan Lab has shown CoM, when applied to plants at the roots or at the leaves, stimulates growth, increases CO2 uptake, mitigates nonphotochemical quenching, and increases hormones resulting in increased photosynthetic efficiency. The Buan Lab engineered E. coli bacterium to synthesize CoM and showed improved resistance to oxidative stress. These data show plants and bacteria benefit through CoM, suggesting CoM may have broad application for increasing crop yields and for microbial fermentation across a wide range of organisms relevant to agriculture and biomanufacturing.

Biomass processing for lignocellulosic fuel and oil production

Extremophilic microbes are a rich source of bioengineering traits that can harnessed for the bioeconomy. Currently, enzymes for processing biomass are the major cost associated with ethanol production. The Buan Lab in collaboration with UNL colleagues has developed a proprietary enzyme cocktail, Extremase, that is effective on a wide variety of biomass: corn, switchgrass, sorghum, soybeans, nut shells, etc. Extremase can also be boiled while maintaining activity, and therefore has potential to decrease the cost and water needed to produce a gallon of ethanol. Extremase may be widely applicable for biomass processing for oil and ethanol fermentation (or other microbial chemical fermentations) and anaerobic digestion. The Buan Lab has spun out a startup company, Molecular Trait Evolution, to further commercialize use of Extremase enzymes for oil and sugar processing. Academic research is ongoing to engineer crops for increased feed and fuel efficiency, and to engineer other extremophilic enzymes for a wide variety of bioeconomy applications.

 

Publications

Peer-reviewed research manuscripts

  1. Fiore, N.A., Kohtz, A.J., Miller, D.N., Antony-Babu, S., Pan, D., Lahey*, C., Huang, X., Lu, Y., Buan, N.R., and K.A. Weber. 2025. Microbial methane production from calcium carbonate at moderately alkaline pH. Nature Commun Earth Environ 6, 85 (2025). https://doi.org/10.1038/s43247-025-02057-y.
  2. Brown, J., Vijayan, J., Rodrigues de Quieroz, A., Ramos, N.F., Bickford, N., Wuellner, M., Glowacka, K., Buan, N.R., Stone, J.M., and R.L. Roston. 2025. Coenzyme M: An archaeal antioxidant as an agricultural biostimulant. Antioxidants 2025, 14(2), 140; https://doi.org/10.3390/antiox14020140.
  3. Buan, N.R. and W.W. Metcalf. Transcriptional response of Methanosarcina acetivorans to repression of the energy-conserving methanophenazine:CoM-CoB heterodisulfide reductase enzyme HdrED. Microbiology Spectrum. Oct 0:e00957-24. https://journals.asm.org/doi/10.1128/spectrum.00957-24.
    1. Featured in the ASM Journals SDG Spotlight Article Collection focused on Affordable and Clean Energy (SDG7). https://journals.asm.org/asm-sdg-spotlight-collection.
  4. Salvi, A.M., Chowdhury, N.B., Saha, R., and N.R. Buan. 2023. Supplementation of sulfide or acetate and 2-mercaptoethane sulfonate restores growth of the Methanosarcina acetivorans ΔhdrABC deletion mutant during methylotrophic methanogenesis. Microorganisms. 11(2), 327. https://doi.org/10.3390/microorganisms11020327.
  5. Catlett, J.L., Carr, S.C., Cashman, M., Smith, M., Walter, M.E., Sakkaff, Z., Kelley, C., Pierobon, M., Cohen, M.B., and N.R. Buan. 2022. Metabolic synergy between human symbionts Bacteroides and Methanobrevibacter. Microbiol Spectr. May 10:e0106722. doi: 10.1128/spectrum.01067-22. PMID: 35536023.
    1. Featured in: Microbiology: An Evolving Science. Slonczewski, J.L., Foster, J.W, and Zinser, E.R., eds. W.W.Norton. 7th ed.
  6. Carr, S.C., Aldridge, J., and N.R. Buan. 2021. Isoprene production from municipal wastewater biosolids by engineered archaeaon Methanosarcina acetivorans. Appl Sci. 11(8), 3342. DOI:10.3390/app11083342.
  7. Aldridge, J., Carr, S., Weber, K.A., and N.R. Buan. 2021. Anaerobic production of isoprene by engineered Methanosarcina spp. archaea. Appl Environ Microbiol. 87(6) e02417-20. DOI: 10.1128/AEM.02417-20.
  8. Catlett, J.L., Catazaro, J., Cashman, M., Carr, S.C., Powers, R., Cohen, M.B., and N.R. Buan. 2020. Metabolic feedback inhibition influences metabolite secretion by the human gut symbiont Bacteroides thetaiotaomicron. mSystems. 5(5) e00252-20. DOI: 10.1128/mSystems.00252-20.
  9. Buan, N.R., Weber, K.A., Aldridge, J.T., and Carr, S.C. 2018. Production of bioisoprene from wastewater. Water Research Foundation. ISBN: 978-1-94124-296-4.
  10. Duszenko, N., and N.R. Buan. 2017. Physiological evidence for isopotential tunneling in the electron transport chain of methane-producing archaea. Appl Environ Microbiol. 83(18) e00950-17. DOI: 10.1128/AEM.00950-17. PMID: 28710268.
  11. Sakkaff, Z., Catlett, J.L., Cashman, M., Pierobon, M., Buan, N.R., Cohen, M.B., and C.A. Kelley. 2017. End-to-end Molecular Communication Channels in Cell Metabolism: an Information Theoretic Study. ACM NanoCom. DOI: 10.1145/3109453.3109474.Best Paper Award.
  12. Cashman, M., Catlett, J.L., Cohen, M.B., Buan N.R., Sakkaff, Z., Pierobon, M., and C. Kelley. 2017. BioSIMP: Using Software Testing Techniques for Sampling and Inference in Biological Organisms. 12th International Workshop on Software Engineering for Science (SE4Science). DOI: 10.1109/SE4Science.2017..9.
  13. Walter, M.E., Ortiz, A., Sondgeroth, C., Sindt, N., Duszenko, N., Catlett, J.L., Zhou, Y., Valloppilly, S., Anderson, C., Fernando, S., and N.R. Buan. 2016. High-throughput mutation, selection, and phenotype screening of methanogenic archaea. J Microbiol Methods. 131: 113-121. PMID: 27771305.
  14. Pierobon, M., Sakkaff, Z., Catlett, J.L., Buan, N.R. 2016. Mutual Information Upper Bound of Molecular Communication Based on Cell Metabolism. Institute of Electrical and Electronics Engineers (IEEE) 17th International Workshop on Signal Processing Advances in Wireless Communications (SPAWC 2016). DOI:10.1109/SPAWC.2016.7536835.
  15. Aldridge, J.T., Catlett, J.L., Smith, M.L., and N.R. Buan. 2016. Methods for detecting methane production and consumption by gas chromatography. Bio-Protocol. 6(7): e1779. http://www.bio-protocol.org/e1779. PMID: 27771305.
  16. Shea, M.T., Walter, M.E., Duszenko, N., Ducluzeau, A.-L., Aldridge, J., King, S K. and N.R. Buan. 2016. pNEB193-derived suicide plasmids for gene deletion and protein expression in the methane-producing archaeon, Methanosarcina acetivorans. Plasmid. 84-85: 27-35. doi:10.1016/j.plasmid.2016.02.003. PMID: 26876941.
  17. Catlett, J.L., Ortiz, A.M., and N.R. Buan. 2015. Rerouting cellular electron flux to increase the rate of biological methane production. Appl Environ Microbiol. 81(19):6528-37. PMID: 26162885.
  18. Lieber, D.J., Catlett, J., Madayiputhiya, N., Nandukumar, R., Lopez, M.M., Metcalf, W.M., and N.R. Buan. 2014. A multienzyme complex channels substrates and electrons through acetyl-CoA and methane biosynthesis pathways in Methanosarcina. PLOS ONE. 9(9): e107563. PMID: 25232733.
  19. Buan, N.R. and W.W. Metcalf. 2010. Methanogenesis by Methanosarcinaacetivorans involves two structurally and functionally distinct classes of heterodisulfide reductase. Mol. Microbiol. 75:843-53. PMID: 19968794.
  20. Ruiz-Sánchez, P., Mundwiler, S., Spingler, B., Buan, N.R., Escalante-Semerena, J.C., and R. Alberto. 2008. Syntheses and characterization of vitamin B12-Pt(II) conjugates and their adenosylation in an enzymatic assay. J. Biol. Inorg. Chem. 13:335-47. PMID: 18060564.
  21. Buan, N.R. and J.C. Escalante-Semerena. 2006. Purification and initial biochemical characterization of the ATP:cob(I)alamin adenosyltransferase (EutT) enzyme of Salmonella enterica. J. Biol. Chem. 281:16971-77. PMID: 16636051.
  22. Buan, N.R., Rehfeld, K., and J.C. Escalante-Semerena. 2006. Studies of the CobA-type ATP:Co(I)rrinoid Adenosyltransferase enzyme of Methanosarcina mazei strain Gö1. J. Bacteriol. 188: 3543-50. PMID: 16672609.
  23. Buan, N.R. and J.C. Escalante-Semerena. 2005. Computer-assisted docking of flavodoxin with the ATP:Co(I)rrinoid adenosyltransferase (CobA) enzyme reveals residues critical for protein-protein interactions but not for catalysis. J. Biol. Chem. 280: 40948-56. PMID: 16207720.
  24. Stich, T.A., Buan, N.R., Escalante-Semerena, J.C., and T.C Brunold. 2005. Spectroscopic and Computational studies of the ATP:corrinoid adenosyltransferase (CobA) from Salmonella enterica: insights into the mechanism of adenosylcobalamin biosynthesis. J. Am. Chem. Soc. 127: 8710-19. PMID: 15954777.
  25. Stich T.A., Buan N.R., and T.C. Brunold. 2004. Spectroscopic and computational studies of Co2+corrinoids: spectral and electronic properties of the biologically relevant base-on and base-off forms of Co2+cobalamin. J. Am. Chem. Soc. 126: 9735-49. PMID: 15291577.
  26. Buan N.R., Suh S.-J., and J.C. Escalante-Semerena.  2004. The eutT gene of Salmonella enterica encodes an oxygen-labile, metal-containing ATP:corrinoid adenosyltransferase enzyme. J. Bacteriol. 186: 5708-14. PMID: 15317775.
  27. Basha,E., Lee, G.J., Breci, L.A., Hausrath, A.C., Buan, N.R., Giese, K.C., and E. Vierling. 2004. The identity of proteins associated with a small heat shock protein during heat stress in vivo indicates that these chaperones protect a wide range of cellular functions. J. Biol. Chem. 279: 7566-75. PMID: 14662763.
  28. Friedrich, K.L., Giese, K.C., Buan*, N.R., and E. Vierling. 2004. Interaction between small heat shock protein subunits and substrate in small heat shock protein-substrate complexes. J. Biol. Chem. 279: 1080-89. PMID: 14573605.
  29. Stich T.A., Brooks, A.J., Buan, N.R., and T.C. Brunold. 2003. Spectroscopic and computational studies of Co3+-corrinoids: spectral and electronic properties of the B12 cofactors and biologically relevant precursors. J. Am. Chem. Soc. 125: 5897-5914. PMID: 12733931.
  30. Fonseca M.V., Buan, N.R., Horswill, A.R., Rayment, I.  and J.C. Escalante-Semerena. 2002. The ATP:co(I)rrinoid adenosyltransferase (CobA) enzyme of Salmonella enterica requires the 2’-OH group of ATP for function and yields inorganic triphosphate as its reaction byproduct. J. Biol. Chem. 277: 33127-31. PMID: 12080060.

Peer reviewed book chapters, reviews and other works

  1. Engineering Biology Research Consortium. 2024. Engineering Biology for Space Health. https://roadmap.ebrc.org/engineering-biology-for-space-health/.
  2. E. Aurand, Moon, T.S, Buan, N.R., Solomon, K.V., Köpke, M., and EBRC Technical Roadmapping Working Group. 2024. Addressing Climate Change Through Engineering Biology. npj Climate Action 3,9 https://doi.org/10.1038/s44168-023-00089-8.
  3. Brown, J., Hines, C., Rodrigues de Queiroz, A., Sahay, S., Vijayan, J., Stone, J.M., Bickford, N., Wuellner, M., Glowacka, K., Buan, N.R., and R.L. Roston. 2023. The Effects of Exogenously Applied Antioxidants on Plant Growth and Resilience. Phyt Rev. doi: 10.1007/s11101-023-09862-3.
  4. Engineering Biology Research Consortium. 2023. An Assessment of Short-Term Milestones in EBRC’s 2019 Roadmap, Engineering Biology. https://roadmap.ebrc.org/2019-roadmap/an-assessment-of-engineering-biology-2023/.
  5. Carr, S. and N.R. Buan. 2022. Insights into the biotechnology potential of Methanosarcina. Frontiers in Microbiology. https://doi.org/10.3389/fmicb.2022.1034674.
  6. Engineering Biology Research Consortium. 2022. Engineering Biology for Climate and Sustainability: A research roadmap for a cleaner future. https://roadmap.ebrc.org/engineering-biology-for-climate-sustainability.
  7. Sagues, W.J. and A. Woodley. 2022. Hoke, K.L., Zimmer, S.L., Roddy, A.B., Ondrechen, M.J., Williamson, C.E., and N. R. Buan. 2022. Reintegrating Biology Through the Nexus of Energy, Information and Matter. 2022. Integr Comp Biol. Feb 5;61(6):2082-2094. doi: 10.1093/icb/icab174. PMID: 34374780. Authorship determined by random order.
  8. White, K., McEntire, K., Buan, N.R., Robinson, L., and E. Barbar. 2022. Charting a new frontier integrating mathematical modeling in complex biological systems from molecules to ecosystems. Integr Comp Biol. Feb 5;61(6):2255-2266. doi: 10.1093/icb/icab165. PMID: 34283225. Authorship determined by random order. 
  9. Buan, N.R. 2018. Methanogens: Pushing the boundaries of Biology. Emerging Topics in Archaeal Biology. Biochemical Society/Portland Press. 2: 629–646. DOI: 10.1042/ETLS20180031.
  10. Buan, N.R., Kulkarni, G., and W.W. Metcalf. 2011. Genetic methods for Methanosarcina species. In: Rosenzweig, A. and S. Ragsdale, eds. Methods in Methane Metabolism (Methods in Enzymology). 494:23-42. PMID: 21402208.
  11. Escalante-Semerena, J.C., Woodson, J.D., Buan, N.R., and C.L. Zayas. 2009. Conversion of cobinamide into coenzyme B12. In: Warren M.J., Smith A.G., eds. Tetrapyrroles: Birth, Life and Death. Austin/New York: Landes Bioscience/Springer Science+Business Media, 2009:300-16.

Preprints, software, technical reports, and non-peer reviewed manuscripts 

  1. Fiore, N.A., Kohtz, A.J., Miller, D.N., Antony-Babu, S., Pan, D., Lahey, C., Huang, X., Lu, Y., Buan, N.R., and K.A. Weber. 2024. Microbial methane production from calcium carbonate at moderately alkaline pH. Preprint, 16 August 2024, https://doi.org/10.21203/rs.3.rs-4790757/v1.
  2. Buan, N.R., and U. Kappler. 2023. Rising stars in microbial physiology and metabolism 2022. Frontiers in Microbiology. https://www.frontiersin.org/articles/10.3389/fmicb.2023.1254900/full
  3. Sakkhaff, Z. Freiburger, A., Catlett, J.L., Cashman, M., Immaneni, A., Buan, N.R., Cohen, M., Henry, C., and M. Pierobon. 2023. A Molecular Communication model for cellular metabolism. bioRxiv. https://doi.org/10.1101/2023.06.28.546976.
  4. Buan, N.R. 2022. Course Portfolio for BIOC934: Genome Dynamics and Gene Expression. Department of Biochemistry, University of Nebraska-Lincoln. https://digitalcommons.unl.edu/prtunl/210/.
  5. Hoke, K.L., Zimmer, S.L., Ondrechen, M.J., desGeorges, A., Roddy, A.B., Buan, N.R., Williamson, C.E. 2019. Reintegrating Biology Through the Nexus of Information and Energy. NSF Reintegrating Biology Jumpstart. https://reintegratingbiology.org/vision-papers/ *authorship determined by random order.
  6. White, K., McEntire, K., Buan, N., Ghosh, K., Robinson, L., and E. Barbar. 2019. Charting a new frontier of science by integrating mathematical modeling to understand and predict complex biological systems. NSF Reintegrating Biology Jumpstart. https://reintegratingbiology.org/vision-papers/ *authorship determined by random order.
  7. Cashman, M., Catlett, J.L., Cohen, M.B., Buan, N., Sakkaff, Z., Pierobon, M., and C. Kelley. 2016. Sampling and Inference in Configurable Biological Systems: A Software Testing Perspective. Computer Science & Engineering, University of Nebraska-Lincoln, Technical Report #TR-UNL-CSE-2016-0007.
  8. Pierobon, M., Cohen, M.B., Buan, N. and Kelley, C. 2015. SCIM: Sampling, Characterization, Inference and Modeling of Biological Consortia. Computer Science & Engineering, University of Nebraska-Lincoln, Technical Report #TR-UNL-CSE-2015-0002.

Inventions and patents

  1. Carr, S., Andrade, M., Hilbers, B., Clemente, T., Blum, P., and N.R. Buan. 2024. “Extremase corn lines to improve lignocellulose deconvolution and release of oil.” NUTech Ventures.
  2. Carr, S., Buan, N.R., and P. Blum. 2024. “Increasing Soybean Oil Yields by Extremase Bioprocessing.” NUTech Ventures.
  3. Hines, C., Roston, R., Erickson, D. and N.R. Buan, 2024. Synthetic operon for the production of 2-mercaptoethane sulfonate (coenzyme M). US patent application 63/659,271.
  4. Rodriguez de Quieroz, A., Brown, J., Vijayan, J., Hines, C. Ramos*, N.F., Stone, J.M., Bickford, N. Glowacka, K., Buan, N.R., and R. Roston. 2024. Use of a small, effective antioxidant to increase plant and microbial biomass. US patent application 63/659,175.
  5. Aldridge, J., Carr, S., Weber, K.A., and N.R. Buan. 2019. “Production of Isoprene by Methane-producing Archaea”. US patent US20170175145 B2. 
  6. Catlett, J.L. and N.R. Buan. 2017. “Microbial strains and methods for making and using”. US patent US9598678 B2.
  7. Aldridge, J., Carr, S., Weber, K.A., and N.R. Buan. 2016. “Production of Isoprene by Methane-producing Archaea”. US patent US20170175145 A1.
  8. Aldridge, J., Carr, S., Weber, K.A., and N.R. Buan. 2015. “Production of Isoprene by Methane-producing Archaea”. US provisional patent 62/271,151.
  9. Catlett, J.L. and N.R. Buan. 2015. “Microbial strains and methods for making and using”. US patent US20150299673 A1. 
  10. Catlett, J.L. and N.R. Buan. 2014. “Microbial strains and methods for making and using”. US provisional patent 61/980,656. 

Education and Outreach

Public and K-12 Outreach and Recruiting

NSF REU Bioenergy Summer Research Program

NSF REU Redox Biology Summer Research Program

Women in Science Conference for Nebraska high school women

Nebraska State Museum Dinosaurs and Disasters “Microbes Rock”

University of Nebraska State Museum Sunday with a Scientist “Seeing the Unseen”

TRIO-Upward Bound Math Science pre-college program

First Year Research Experience (FYRE) program 

Formal Teaching Responsibilities, University of Nebraska-Lincoln

BIOC 435 Advanced Topics in Biochemistry (ACE 10) Coenzymes and Cofactors

BIOC/BIOS/CHEM 934 Genome Dynamics and Gene Expression

BIOC 205 Scientific Writing and Analysis

BIOC 992K Graduate Seminar

Guest Lectures and Other Institutional Instruction

BIOS 421/821 MBIO 421 Microbial Diversity “Methanogens”, UNL

BIOS 180 Biological Sciences Learning Community Freshman Seminar, UNL

PLSC 811 Current Topics in Microbiology, University of Delaware

CHME 499 Senior Capstone, UNL

BIOC101 Career Opportunities in Biochemistry, UNL

AST 113 Life in the Universe, UNL

Redox Biology Summer course “Redox biodiversity”, UNL/Karolinska Institute

Ethics and Responsible Conduct in Research, UNL

People