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31st Symposium on Biotechnology for Fuels and Chemicals; Some New Approaches for Producing Butanol

The 31st Symposium on Biotechnology for Fuels and Chemicals, a special conference of the Society for Industrial Microbiology, began yesterday in San Francisco with its largest group of conferees yet—approximately 850.

The academic conference, hosted by the National Renewable Energy Laboratory (NREL), runs through Wednesday and features a large technical program, comprising fourteen dual sessions for the presentation of papers and approximately 400 posters. Technical topics range from plant, enzyme and microbial science and technology to biomass pretreatment to biorefinery deployment and sustainability issues. A great deal of the focus of the event is on optimizing different aspects of cellulosic ethanol production.

Among the sponsors this year is the Energy Biosciences Institute (earlier post), which helped bring the meeting to San Francisco by defraying hotel costs for many of the academics.

This year’s conference, noted NREL’s Jim McMillan, one of the Conference Chairmen comes at a stimulating yet also confounding time.

The attendance at this meeting is a testament to the importance of the topic and the dedication of the people in this room...Every day, every week, new developments in biotechnologies are allowing us to go to a greater variety of fuels and chemicals with better efficiencies. It is a very exciting time. On the other hand, biofuels and biotech are at the leading front of sustainability issues. Renewable resources, lignocellulosics, are at the intersection of agriculture, energy and environment.

Some of the resultant attention has not been all that positive, McMillan noted, and biofuels researchers can be feeling a bit beleaguered now.

As part of this meeting, we will come out with a renewed sense of the possibility and potential, and a collective message that we can bring forward. We know we can do biofuels wrong; the challenge to all of us is how to do them right.

We need to bring the word conservation [back] in. How large [biofuels] can be as contributors to a renewable society depends on the demand side too...We know as experimentalists that there are no linear issues.

—Jim McMillan

Biobutanol. Among the papers presented in one of the twin opening oral presentation sessions were several describing potential new engineered genetic pathways to produce biobutanol.

Biobutanol continues to attract interest based on its properties compared to ethanol such as its higher energy content, the ability to be transported in existing pipelines, and the ability to blend at higher ratios without impacting engine performance. At least one company, Gevo, is also looking at butanol as an intermediate to renewable hydrocarbon fuels. (Earlier post.)

The conventional microbial producer of butanol is Clostridium acetobutylicum, which generates three products: acetone, butanol and ethanol (ABE fermentation). Commercial biobutanol production has several limitation, including low values for final product concentration and degradation stemming from the toxicity of butanol to organisms.

One of the challenges many researchers are trying to tackle is enabling yeast to ferment the pentose sugars derived from cellulosic biomass. Dr. Eckhard Boles from Goethe Universtät Frankfurt am Main described the cloning and successful expression of a xylose isomerase with high activity in the industrial yeast Saccharomyces cerevisiae to enable the yeast to ferment the C5 sugars (found in high concentrations in cellulosic biomass). The research team, working with Butalco (earlier post) isolated the corresponding gene from the anaerobic bacterium Clostridium phytofermentans.

[The use of C. phytofermentans as a source prompted a conferee from Qteros to declare himself “shocked and surprised” during the Q&A session on Boles’ presentation, since Qteros has an exclusive patent on C. phytofermentans. Qteros, formerly known as SunEthanol, is commercializing a consolidated bio-processing (CBP) technology based on the “Q Microbe” (C. phytofermentans). (Earlier post.)]

Although the initial output of the project is targeted to be ethanol, Boles said that they were considering a butanol pathway as well, and have already engineered yeast that deliver butanol.

Eric Steen, a graduate student at UC Berkeley studying under Dr. Jay Keasling, described engineering S. cerevisiae for the production of n-butanol by implementing an n-butanol biosynthetic pathway. To develop the new pathway, Steen and colleagues worked with isozymes from a number of different organisms (S. cerevisiae, E. coli, C. beijerinckii, and R. eutropha).

In addition, several posters addressed butanol production:

  • Rice University presented a study on the co-production of riboflavin (a high-value coproduct) during fermentation of genetically modified C. acetobutylicum.

  • The Korea Institute of Science and Technology described the development of a two-phase fermentation system for stable and high biobutanol production using a strain of C. acetobutylicum. The system features liquid-liquid extraction for the in-situ removal of butanol from batch-fed reactor broth.

  • UC Berkeley, Lawrence Berkeley National Laboratory and the Joint BioEnergy Institute presented a strategy for the development of an in vivo biosensor to boost butanol production from E. coli.


  • E. Boles, D. Brat and B. Wiedemann. Construction of pentose fermenting industrial Saccharomyces cerevisiae strains expressing a bacterial xylose isomerase (Presentation 2-04)

  • E.J. Steen, R.C. Chan, N.P. Prasad, S. Myers, C. Petzold, A. Redding, M. Ouellet and J.D. Keasling. Metabolic engineering of Saccharomyces cerevisiae for the production of n-butanol (Presentation 2-06)

  • X. Cai and G. Bennett. Riboflavin production during fermentation of genetically modified biobutanol-producing Clostridium acetobutylicum (Poster 2-54)

  • S.M. Lee, M.O. Cho, Y. Um and B.I. Sang. Development of two phase fermentation system for the stable and high butanol production using Clostridium acetobutylicum ATCC824 (Poster 2-59)

  • J.A. Dietrich, D.L. Shih, A. Chan and J.D. Keasling. Design of transcription factor-based in vivo biosensors for improved butanol production in E. coli (Poster 2-70)



"W2 Energy Inc., the developer of a GAT (Gliding Arc Tornado) plasma reactor for biomass gasification for power and fuels generation, is working to manufacture biobutanol from the GAT syngas."

I had to search a bit to come up with someone gasifying biomass to butanol, but apparently it can be done.


Not only can you mix butanol with gasoline and diesel you can use it to help mix in ethanol as a third renewable ingredient to diesel.
The limit to mixing ethanol into diesel is that at a low % it separates, more so in cold weather. It turns out ethanol dissolves in butanol, and butanol (with ethanol) in diesel, so you can get a much higher ethanol % without using costly emulsifiers.
If you had unlimited bio-butanol you may not bother with this approach. However as there is still very little bio-buatanol available such mixing allows a higher renewable content diesel with finite butanol supplies. Helps combustion and emissions too.

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