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Team:Edinburgh/FAQ
From 2008.igem.org
Frequently Asked Questions
Q. Why should the entire process be contained in just one organism that does not naturally do the reactions you want, and is therefore probably going to be inefficient, when you could have do the process in steps using different types of organism for each step?
A. The reasons for combining the process into a single host are many. A proportion of the product of each step would be lost with each purification, so although the organisms themselves maybe more efficient, efficiency would be lost. Coupled to this is the difficulty of purifying some of the products. For instance, glucose is soluble, and therefore difficult to purify from solution, as is glycogen. Starch on the other hand is highly insoluble making purification of this end product relatively straight forward.
Q. If one aim is to have your product converted into ethanol as a biofuel, why should the biomass be converted all the way to starch rather than simply stopping at glucose, which is easy to ferment to ethanol?
A. Again, there is a question of purification here (see previous question), but as well as this, glucose becomes inhibitory at high concentrations due to osmotic pressure, and may also cause product inhibition of reactions which produce it. Starch, being insoluble, can accumulate at much higher quantities without disrupting the biochemistry of the cell (we hope).
Q. In that case, why not just add in an ethanol production pathway and go straight from cellulose to ethanol?
A. That would be possible, and we could try that in future when we get the cellulose degradation module working. But basically we see starch production as being much more flexible. Conversion of cellulose to ethanol is a 2-stage process - conversion of cellulose to glucose (slow and difficult) and conversion of glucose to ethanol (fast and easy). By having a separate process for conversion of cellulose to starch (which can later be easily and cheaply converted to glucose) we separate out the slow, difficult step and produce an high density, easily transportable and versatile product (starch) which can then be transported to other sites for easy in-situ conversion to glucose and fermentation to produce not only ethanol but also potentially a wide variety of other products, such as butanol, biodegradable plastics, and next generation biofuels such as the terpenoid-derived liquid fuels being developed by Amyris, the long chain alcohols being developed by LS9, and the 'Microdiesel' under development by A. Steinbuchel's group. We see our technology as a key enabling technology which can be combined with other biofuel projects to create the next generation, fully renewable carbon economy, with starch as the key distributable intermediate. And of course, starch also offers the potential of a food or animal feed product.
Q. Why do so many people tell me that Edinburgh is the best city in the world?
A. Because it is. Really. Come and see!
