Background
We have been bothered for a long time by the unpleasant odor generated when we cultivate E. coli.
Therefore, we wondered if it would be possible to make the experiment more pleasant by development of E. coli biosynthesize aromatic component.
In terms of what kind of aroma we wanted to give it, we chose the vanilla scent because we all are familiar with it in puddings and ice cream.
We researched vanilla fragrance and found that a compound called vanillin is the main aromatic component.
Vanillin is a compound of the vanilloid family and accumulates as a glycoside in the orchid plant, vanilla bean.
After the vanilla bean is harvested, the glycosides are hydrolyzed through a process called curing, which releases vanillin and produces an aroma.
Vanillin, which is obtained from vanilla, is considered a very rare flavoring agent because of the time and effort required to grow vanilla and the curing process.
It takes several years for vanilla to bear fruit, and the curing process requires 1 to 6 months. The fact that only a small amount of vanillin can be obtained per vanilla bean makes vanillin very rare.
As a result, more than 99% of the vanilla in the market is now made up of vanillin that is chemically synthesized from precursors or produced by incorporating genes into yeast and other organisms.
To get E. coli to synthesize vanillin, we had to decide what to use as a precursor.
Three candidates were identified: ferulic acid, amino acids such as phenylalanine and tyrosine, and glucose.
Ferulic acid, phenylalanine, and tyrosine are expensive. On top of that E. coli dose not have many of the genes needed for the pathway from phenylalanine and tyrosine to vanillin.
We chose to start from glucose because we found that if we started with glucose, the raw materials could be synthesized at a lower cost and using the shikimic acid pathway.