Microbiology of synthesis gas fermentation for biofuel production

1. Microbiology of synthesis gas fermentation for biofuel production 朱琴娥 2008.05.14

2. Background What we shoud do with these problem?

3. What way we can obtain clean and sustainable energy supply?

4. MethodⅠ Shorting: the conversion rate is very low.

5. biomass coal Fossil fuels Gasification Gasification chemistry Syngas Acetate Butyrate Ethanol Others production MethodⅡ Source and application of syngas

6. Syngas (CO,H2O)

7. WGS: Syngas fermentation • Higher specificity biocatalysting • Lower energy costs • Resistance to catalyst poisoning • Independence of a fixed H2:CO ratio

8. For example: Clostridium ljungdahlii commercial process step: • Biomass gasification • Syngas fermentation • Distillation of ethanol from the reactor effluent

9. Question? Sparingly soluble gases result in low conversion rate…… • High gas and liquid flow rates • Large specific gas–liquid interfacial areas • Increased gas solubility (increased pressure or solvents) The way of stimulate gas/liquid mass transfer rate

10. Continuous stirred tank reactors (CSTR) • Monolith biofilm reactors • Membrane biofilm reactor (MBfR) • Biotrickling filter

11. Carboxydotrophic thermophiles Before Recently Carboxydocella sporoproducens Archaeoglobus fulgidus Desulfotomaculum carboxydivorans Thermoanaerobacter tengcongensis carboxydotrophic hydrogenogens both convert CO to acetate optimum growth temperatures of 55 ℃ and 80℃ optimum growth temperatures of 55 ℃ and 80℃ Chemolithoautotrophically through the conversion of CO and H2O to H2 and CO2. doubling times of 10 h and 7 h growth rates between 1 and 2 h others might also grow organotrophically encode CO dehydrogenases

12. The acetyl-CoA pathway and CO dehydrogenase

13. oxidation ADP CO2 CO Dehydrogenation NADPH NADP+ ATP Metabolic engineering Metabolic engineering of these organisms with the aim of producing of a specific compound can thus be accompanied by the formation of undesired byproducts, which are formed to satisfy the redox balance Additional separation techniques are then required to obtain a purified product.

14. Conclusions • Syngas fermentation is an attractive technology for the production of biofuels and chemicals. • A process for ethanol production from syngas is already available, and pureH2 production is possible as well. • At present, suitable thermophiles for the production of organic compoundsfrom syngas are not available, although their use could offer potential advantages over the use of mesophiles. • Thermophiles that employ CO as a substrate for theproduction of chemicals could be selected based on theidentification of CO dehydrogenase genes in their genome. • Better still would be the isolation of new thermophiles that use CO or syngas as a substrate at conditionsthat resemble expected bioreactor conditions.

15. Thank you!