To develop strains of bacteria that produce high levels of 1-butanol we have introduced the genes coding for a biochemical pathway from Clostridium acetobutylicum into a mutant E. coli strain that produces a high level of NADH.The combination of these chemical pathways is predicted to increase the level of butanol production.. >>
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The Etch-a-Sketch project aims to create a lawn of bacteria that can be drawn on with a laser pointer. This seemingly inconsequential task actually presents many interesting engineering challenges. We have designed a novel genetic switch to tackle these problems. If our work proves successful, it will serve as a useful model for future projects that require large signal amplification.
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This summer, we have conducted the following experiments regarding the biofuels in bacteria project.
CALIBRATION CURVE FOR N-BUTANOL HEXANE EXTRACTION
The calibration curve was designed to determine how much 1-butanol was extracted by hexane. This was performed using gas chromatography. This method of measurement is a common type of chromatography used in analytical chemistry for analyzing vaporized compounds without decomposition.
The most common method of detection is flame ionization detection and is sensitive to a wide variety of compounds. This was the ideal measurement device for 1-butanol measurement.
n-Butanol Production
We concluded that the mutant strain produced a significantly higher amount of 1-butanol than the wild type. These results were extrapolated from three samples and three hexane extractions from the same culture.
This allows us to control for errors in the extraction and measurement, but not for potential variations between independent cultures. The mutant strain of E. coli (JCL) produced a yield of 128.08 +/-5.4 ug/ml/OD; the wild type (DH5 alpha) strain of E. coli produced a yield of 93.81+/- 1.5 ug/ml/OD per cell.
Confirmation of the Benefit of Ter Function of 1-Butanol Production
The ter gene originally from Treponema denticola is a trans-2-enl-CoA reductase. Its functional portion of this project is to convert an intermediate of Crotonyl-CoA into Butyryl-CoA.
This part has been submitted to the parts registry and is proven to be functional as our assay with the final project shows a statistically significant production of 1-butanol. We have proven that the use of this gene in the circuit does in fact allow the transformed cell to produce the desired product. Since the gene is NADH dependent, we can presume that the NADH-surplus mutant strain generates feeds into this gene and produces a higher net result of 1-butanol.
Butanol Production in E. Coli
We have focused on implementing a 1-butanol producing biochemical pathway, initially found in Clostridium, into the very well known model organism E. coli.