For biofuels to be economical, we will need some technology breakthroughs. In the US, the RFS is driving us to produce liquid fuel, usually with enzymes that convert sugars and starches in the biomass to ethanol or other liquid molecules we can burn in engines. One cool approach I’ve mentioned before is to engineer feedstocks to contain enzymes that break down the biomass (avoiding costly pretreatment before processing into a liquid fuel). Sometimes these company press releases are total bullsh*t, but now this company has published their results in a peer reviewed journal (and a really good one – impact factor 23.2 for 2011) for us to see all the details.
First, I think it is really good that they are targeting corn stover – what is leftover after harvesting the grain. This avoid food vs. fuel issues. In order to have the plants express the enzyme (xylanase) that breaks down the biomass ONLY during processing (and not when the plant is trying to grow), they had to engineer the enzyme with a piece of a bacterial gene that spliced itself out and allowed the enzyme to be active only above a certain temperature (60C, 140F). This makes the pretreatment pretty easy – all you need is warm water. The costs that they can avoid with just water are significant:
- costs of enzymes (~$0.50–$1.47/gal)
- pretreatment (estimated at >$0.30/gal)
They found that they got 20% more yield from the plants. I think there is room for more improvement, since the dormant enzyme still shows some activity at normal temperatures (when the plant would be in the field).
I think this is a really great advance – innovative use of biotechnology to solve a real world problem!
Check it out here:
Shen, B., Sun, X., Zuo, X., Shilling, T., Apgar, J., Ross, M., Bougri, O., Samoylov, V., Parker, M., Hancock, E., Lucero, H., Gray, B., Ekborg, N., Zhang, D., Johnson, J., Lazar, G., & Raab, R. (2012). Engineering a thermoregulated intein-modified xylanase into maize for consolidated lignocellulosic biomass processing Nature Biotechnology DOI: 10.1038/nbt.2402