Skip to main content

Hybrid Processing Program

Hybrid processing program trading card Iowa State University has established a laboratory in the Biorenewables Laboratory (BRL) Building dedicated to hybrid thermochemical/biological processing of biomass. Faculty and students from the departments of Food Science and Nutrition, Chemical and Biological Engineering, Civil, Construction, and Environmental Engineering, and Mechanical Engineering are collaborating in this interdisciplinary program to convert cellulosic biomass into fuels and chemicals using a combination of thermochemical and biological processes.

The overall goal of this program is to address the demand for production of fuels and commodity chemicals from biomass in a manner that is economically competitive with petroleum-based processes. Traditional biomass processing through biochemical pathway is limited by the high cost of the enzymes that are used to break lignocelluloses down into fermentable sugars. In our process, we use a thermochemical approach (pyrolysis), instead of a biochemical approach (enzymes), to release fermentable substrates, such as syngas, sugars, and acetic acid, from biomass. These fermentable substrates can then be utilized by microbial biocatalysts to produce biorenewable fuels and chemicals.

The two main areas of current research are syngas fermentation and bio-oil fermentation.

Syngas Fermentation

Gasification of carbonaceous feedstocks produces carbon monoxide- and hydrogen rich syngas that can be fermented to various products including carboxylic acids, alcohols, and esters.  The syngas fermentation facility includes onsite sample analysis capabilities and can be used to investigate potential syngas consuming microorganisms.

Due to the low solubility of CO and H2, syngas fermentation is limited by the slow transfer of CO and H2 from the gaseous phase to the liquid phase for microbial utilization.  Hollow fiber membrane biofilm reactors (HFM-BR) and monolithic biofilm reactors (MBR) have special features that lead to increased mass transfer efficiency.  Current efforts are focusing on enhancing mass transfer of syngas fermentation through developing these two types of biofilm-based reactors.

In HFM-BR, syngas is directly diffused through the inner walls of microporous hydrophobic membrane with a large surface area. The membrane also serves as a support for growth of microorganisms attached on the outer wall of the membranes.  Therefore, the microorganisms can consistently access the diffused syngas and the medium nutrients.

In MBR, mass transfer is achieved inside narrow channels of the monolithic packing materials, in which a biofilm is formed one the inner wall, the syngas follows a Taylor flow pattern, and a thin liquid film exists between the elongated gas bubbles and the biofilm.  As the bubble flows through the channel, the liquid film become thinner, it is therefore easier for the gas to diffuse through the reduced liquid boundary layer to the biofilm.  By this unique feature, the mass transfer efficiency of the syngas can be enhanced.

This research is currently funded by the Iowa Energy Center and Iowa State Bailey Foundation.

[PHOTO] Monolithic packing materials  [IMAGE] Monolithic packing materials

Monolithic packing materials used as syngas fermentation for enhanced mass transfer.

Bio-oil Fermentation

The liquid product produced from biomass fast pyrolysis, also known as bio-oil, is rich in sugars and carbohydrates that are attractive substrates for the production of biorenewable fuels and chemicals by microbial biocatalysts (Jarboe et al, 2011). Our program has developed a bio-oil collection method that concentrates these substrates (See Iowa State University News release).

Heavy fraction from the bio-oil recovery systems consist of a mixture of water-soluble sugars derived from plant carbohydrates and water-insoluble phenolic oligomers derived from lignin. We have discovered that the sugars can be separated from the phenolic oligomers by a simple washing process that yields a syrup that contains 20-40 wt% sugar.

Light fraction from the bio-oil recovery systems is an aqueous solution that contains about 10-15 wt% of acetic acid, making it an attractive source of carbon and energy for fermentation.

Existing ethanol-producing biocatalysts have been engineered for the use of bio-oil-associated sugars in a method that can be extrapolated to other biocatalysts. For example, ethanologenic E. coli KO11 was engineered for levoglucosan utilization by recombinant expression of levoglucosan kinase from Lipomyces starkeyi (Layton et al, 2011).

Oleaginous microbes such as algae and yeast have been tested to utilize the acetic acid -rich fractions to produce lipids. For example, Chlamydomonas reinhardtii, an algae strain can grow both heterotrophically and phototrophically was tested for culture with bio-oil for lipid production.

The current hurdle to the success of hybrid processing is the fact that contaminant compounds contained in the substrate streams inhibit the growth and productivity of the microbial biocatalysts. Our efforts are to mitigate this inhibition through two approaches: reducing the abundance of the inhibitory compounds and increasing the biocatalysts’ ability to tolerate these compounds. To reduce the inhibitory compounds, various pretreatment methods are currently being developed for bio-oil containing substrate stream. To enhance the tolerance of microorganism to the inhibitory compounds, we are suing directed revolution strategy to achieve this goal.

This research is currently funded by the NSF Energy for Sustainability program and Iowa State Bailey Foundation.

Scientist in the lab

Metabolic evolution is used to increase biocatalyst tolerance of inhibitory compounds.

Scientist in the lab

Biochemical characterization of bacterial biocatalysts when exposed to inhibitory compounds, with the goal of making the biocatalysts more robust.

Principle Investigators

  • Dr. Laura R. Jarboe, Iowa State University
  • Dr. Zhiyou Wen, Iowa State University

Lab Manager

  • Zhanyou Chi,  Iowa State University

Selected Publications

Donovan Layton, A. Ajjarapu, D.W. Choi, L. Jarboe*.  “Engineering ethanologenic Escherichia coli for levoglucosan utilization”.  Bioresource Technology. 2011, 102: 8318-8322.

Choi, D.-W., DiSpirito, A. A., Chipman, D. C., and Brown,R. C. (2011) Hybrid processing, in Thermochemical Processing of Biomass: Conversion into Fuels, Chemicals, and Power, Brown, R.C. (Ed.), Wiley & Sons.

Choi, D., Chipman, D., Bents, S., Brown, R. (2010) A techno-economic analysis of poly-hydroxyalkanoates and hydrogen production from syngas fermentation of gasified biomass, Applied Biochemistry and Biotechnology 160, 1032-1046.

Deng, W., Zheng, L., Huang, Y., Lin, V.S.-Y., and Brown, R.  (2010) Production of ethanol from biomass-derived syngas, AIChE 2010 annual meeting, Salt Lake City, UT, November 7-12.

Do, Y. S., J. Smeenk, et al. (2007). “Growth of Rhodospirillum rubrum on synthesis gas: conversion of CO to H2 and poly-beta-hydroxyalkanoate.” Biotechnol Bioeng 97(2): 279-86.

Chipman, D., Do, Y., Choi, D., Jones, S., DiSpirito, A., Brown, R.  (2007)  Syngas Fermentation Research Facility at Iowa State University, Biobased Industry Outlook Conference, Ames, IA, November 5-6, 2008.

Chipman, D., Choi, D., Jones, S., Brown, R.  (2008)  Optimization of PHA Production in Rhodospirillum rubrum Cultured on Carbon Monoxide from Synthesis Gas, 30th Symposium on Biotechnology for Fuels and Chemicals, New Orleans, LA, May 3-7, 2008.

Chipman, D., Choi, D., Jones, S., DiSpirito, A., Brown, R.  (2008)  Optimization Strategies for Fermentative PHA Production from Synthesis Gas, 2008 Biobased Industry Outlook Conference, Ames, IA, September 7-10, 2008.

Chipman, D., Choi, D., Jones, S., Brown, R., DiSpirito, A.  (2008)  Hydrogen and Polyhydroxyalkanoate Production in Rhodospirillum rubrum Cultured on Carbon Monoxide from Synthesis Gas, 2008 Biobased Industry Outlook Conference, Ames, IA, September 7-10, 2008.

Chipman, D., Choi, D., Jones, S., Brown, R.  (2008)  Optimization of PHA Production in Rhodospirillum rubrum Cultured on Carbon Monoxide from Synthesis Gas, Presidential Lecture Poster Presentation, Ames, IA, October 27, 2008.

Brown, R. C. (2007) Hybrid thermochemical/biological processing of biomass, Applied Biochemistry and Biotechnology 137-140: 947 – 956.

Brown, R. C., Hybrid Thermochemical/Biological Processing:  Putting the Cart before the Horse? Twenty-Eighth Symposium on Biotechnology for Fuels and Chemicals, Nashville, TN, April 30 – May 3, 2006.

Brown, R. C., Biomass Refineries based on Hybrid Thermochemical/Biological Processing– An Overview, in Biorefineries, Biobased Industrial Processes and Products, Kamm, B., Gruber, P. R., Kamm, M., Eds., Wiley-VCH Verlag, Weinheim, Germany, 2005.

Brown, R. C., Heindel, T., DiSpirito, A., Nikolau, B., “Production of biopolymers and hydrogen via syngas fermentation, National ACS Meeting, Anaheim, California, March 28 – April 1, 2004.

Brown, R. C., Heindel, T., DiSpirito, A., Nikolau, B., “Production of biopolymers and hydrogen via syngas fermentation,” Annual Meeting of the Institute of Biological Engineering, Fayetteville, Arkansas, January 9-11, 2004.

Heindel, T. J., DiSpirito, A. A., Brown, R. C., and Nikolau, B. J., “Biobased products via syngas fermentation,” 25th Symposium on Biotechnology for Fuels and Chemicals, May 4-7, 2003, Breckenridge, CO.

Brown, R. C., A. L. Pometto III, T. L. Peeples, M. Khiyami, B. Voss, J.W. Kim, and S. Fischer. “Strategies for pyrolytic conversion of herbaceous biomass to fermentation products,” Proceedings of the Ninth Biennial Bioenergy Conference, Buffalo, New York, October 15-19, 2000.

Brown, R. C., Pometto, A., and Peeples, T., “Hybrid Thermal/Biological Process for Converting Lignocellulosic Wastes into Fermentation Products,” Getting Value from Ag Biotechnology, 1999 Biotechnology Byproducts Consortium, Des Moines, IA, March 4-5, 1999.

So, K., Brown, R. C., and Scott, D.S., “Economic analysis of ethanol production from switchgrass using hybrid thermal/biological processing,” BioEnergy ’98 Conference, Madison, WI, October 4-8, 1998.

So, K. and Brown, R.C., “Economic analysis of selected lignocellulose-to-ethanol conversion technologies,” Proceedings of the Conference on Biotechnology for Fuels and Chemicals, Gatlinburg, TN, May 4-7, 1998.