Final Report Summary - SYNTOBU (Biological production of butanol from syngas)
The global energy consumption has doubled over the last 30 years, sustained mainly by the use of fossil fuels. The potential depletion of these may leave our society at the edge of an energy crisis unless reliable alternative energy sources are established. Syngas fermentation is a promising approach to produce carbon neutral bio-fuels from organic wastes. As of today, ethanol has been the main target, although butanol has several inherent advantages such as its higher energy content, it can be used directly in existing car engines without substantial modifications, or the lower solubility in water which eases its downstream processing. The main aim of this project was to investigate syngas fermentation to understand how to drive its conversion to the production of butanol.
The project initially focused on the cultivation of several carboxydotrophic strains capable of fermenting syngas into butanol (WP1) to be further used in WP2 and WP3. These were subsequently characterized to assess their kinetics and stoichiometry, their tolerance to different toxics, as well as identify the key parameters driving their metabolism to butanol production (WP2). Among the different strains tested, Clostridium carboxidivorans P7 had the fastest kinetics, although it also proved to be the most sensitive to toxic impurities such as ammonia, micro-aerobic conditions or the accumulation of alcohols, especially butanol. Experiments conducted with different syngas stoichiometries proved the superior production of longer carbon chain products and alcohols in abundance of reducing power, and especially when being fed with CO-rich syngas. Looking at fermentation parameters, pH was proven to play, not only a critical role on product speciation but also on cell productivity, with pH close to neutrality yielding higher production per cell. On the other hand, temperature tests showed that incubation at sub-optimal temperatures allows the production of high concentrations of longer-chain products and alcohols, likely due to the higher availability of reducing power at lower temperatures. Of special interest, C. carboxidivorans P7 incubated at 25 °C not only produced butanol, but also caproate and hexanol. Finally WP3 targeted the production of butanol in lab-scale reactors, and aimed to establish optimal reactor design and operational conditions to produce butanol from syngas. Unfortunately very limited progress was done in this work-package due to the early termination of the project.
In terms of impact of the project, this was basically restricted to the scientific community in the form of publications. Again, the early-termination of the project prevented any potential impact of this research to industry, as the most applied knowledge would have been derived from the successful completion of WP3.
This EU project allowed the fellow to re-integrate in an internationally-recognized research group, to start building his own research team and to further develop his track record with the mentoring of his host supervisor. Unfortunately, the fellow left the host institution due to personal reasons, terminating the project at the end of month 25.
The project initially focused on the cultivation of several carboxydotrophic strains capable of fermenting syngas into butanol (WP1) to be further used in WP2 and WP3. These were subsequently characterized to assess their kinetics and stoichiometry, their tolerance to different toxics, as well as identify the key parameters driving their metabolism to butanol production (WP2). Among the different strains tested, Clostridium carboxidivorans P7 had the fastest kinetics, although it also proved to be the most sensitive to toxic impurities such as ammonia, micro-aerobic conditions or the accumulation of alcohols, especially butanol. Experiments conducted with different syngas stoichiometries proved the superior production of longer carbon chain products and alcohols in abundance of reducing power, and especially when being fed with CO-rich syngas. Looking at fermentation parameters, pH was proven to play, not only a critical role on product speciation but also on cell productivity, with pH close to neutrality yielding higher production per cell. On the other hand, temperature tests showed that incubation at sub-optimal temperatures allows the production of high concentrations of longer-chain products and alcohols, likely due to the higher availability of reducing power at lower temperatures. Of special interest, C. carboxidivorans P7 incubated at 25 °C not only produced butanol, but also caproate and hexanol. Finally WP3 targeted the production of butanol in lab-scale reactors, and aimed to establish optimal reactor design and operational conditions to produce butanol from syngas. Unfortunately very limited progress was done in this work-package due to the early termination of the project.
In terms of impact of the project, this was basically restricted to the scientific community in the form of publications. Again, the early-termination of the project prevented any potential impact of this research to industry, as the most applied knowledge would have been derived from the successful completion of WP3.
This EU project allowed the fellow to re-integrate in an internationally-recognized research group, to start building his own research team and to further develop his track record with the mentoring of his host supervisor. Unfortunately, the fellow left the host institution due to personal reasons, terminating the project at the end of month 25.