Sunday, May 3, 2009
2-41
Characterization of biohydrogen production in metabolically engineered Escherichia coli strains
Juanita Mathews, Department of Molecular Biosciences and Bioengineering, University of Hawai'i Manoa, Honolulu, HI 96822 and Guangyi Wang, Department of Oceanography, University of Hawai'i Manoa, POST 103B, 1680 East West Road, Honolulu, HI 96822.
Microbes have diverse biosynthetic pathways to produce molecular hydrogen and potentially hold the key to the viable macroscale utilization and production of hydrogen from renewable sources. However, low production yield has been a major limiting factor for large-scale biohydrogen production because of various metabolic bottlenecks. Dark fermentations seem to hold the best promise for biohydrogen production due to low costs and relatively high production yields. Because of the availability of metabolic pathway information and took kits for Escherichia coli, this organism was chosen for this study. E. coli strains were engineered for greater production of hydrogen by using a combinatorial strategy of over-expressing the components of the hydrogen-evolving complex, interruption of the uptake hydrogenases, and the elimination of competing metabolic pathways.
We present the results comparing several strains for hydrogen production and metabolite formation during batch fermentations at a constant pressure of 760 mm Hg and utilizing a rich synthetic media. The base strain had uptake hydrogenases 1 and 2 deleted along with hycA, which is responsible for repressing the hydrogen-evolving complex. Additional strains included the over-expression of hycEG, encoding the main subunits of hydrogenase 3, and the interruption of lactate and succinate formation through the elimination of ldhA and frdBC. Acetate production was also interrupted using paired termini antisense RNA against the ackA gene within the acetate kinase-phosphotransacetylase operon. This work provides for the possible application of this knowledge towards developing a commercially efficient hydrogen-producing strain of E. coli.
We present the results comparing several strains for hydrogen production and metabolite formation during batch fermentations at a constant pressure of 760 mm Hg and utilizing a rich synthetic media. The base strain had uptake hydrogenases 1 and 2 deleted along with hycA, which is responsible for repressing the hydrogen-evolving complex. Additional strains included the over-expression of hycEG, encoding the main subunits of hydrogenase 3, and the interruption of lactate and succinate formation through the elimination of ldhA and frdBC. Acetate production was also interrupted using paired termini antisense RNA against the ackA gene within the acetate kinase-phosphotransacetylase operon. This work provides for the possible application of this knowledge towards developing a commercially efficient hydrogen-producing strain of E. coli.