[MUSIC] In this video, we're going to talk about two potential applications of synthetic biology to biofuels. These include biofuels from cellulosic biomass, and biodiesel from an algae. One application of synthetic biology to biofuels development is the use of synthetic biology to improve second-generation biofuels. So, lignocellulose is an extremely abundant biopolymer on earth. And production of lignocellulose feedstock doesn't necessarily compete with food production. So going back to the food versus fuel debate mentioned briefly earlier, so this feedstock, or biomass, can come from waste from existing agricultural or forestry systems. So for example, corn husks, and fast-growing, low-resource grasses that can be planted for this purpose. Synthetic biology can be used to improve the efficiency of fuel development from these feedstocks. This figure simply demonstrates that plant sources, the biomass or feedstock including the leftover corn stalks etc, the cell walls are composed largely of cellulose, hemicellulose, and lignin. Hence, cellulosic biomass. And because plants can turn sunlight into cellulose, sugars, et cetera, you can go from sunlight, which is taken in by plants, to produce cellulose, the cell walls in the plants. Enzymes or microbes could be used to move that cellulose to sugar and ultimately to fuels. And microbes could be used at a couple places in this pathway, including from cellulose to sugar, sugar to fuels. And ideally, there would be a consolidated process where the microbes could be used to get through that whole part of the pathway, from cellulose to fuels. Biodiesel, from cellulosic biomass, is compatible with existing infrastructure, and so meets that goal. Traditionally, biodiesel is produced by the transesterification of triacylglycerols, or TAGs, to make glycerol and fatty acid alkyl esters, or FAAEs. E coli naturally produces fatty acid metabolites, and so can be engineered to produce biodiesel. And again, E coli is, of course, a very well-characterized model organism, for which we have many genetic and other research tools. The second potential application of synthetic biology to biofuels is in third-generation biofuels from algae. So, algae naturally takes sun, carbon dioxide, water, and produces oils, so making it sort of a natural fit for this purpose. Also, there is tremendous diversity among algae. So, algaes include everything from micro-algae up to giant kelp. And even among the micro algae, there are estimated to be hundreds of thousands of species. So there's a tremendous amount of genetic diversity available for scientists to tap into in trying to use algae for production of biodiesel. The yield estimates from algae are higher than they are for other crops. And biofuels from algae can be produced on non-arable lands, so lands that you wouldn't be able to use for farming, and using waste water. Of course, there are concerns, nonetheless, including that you might be shifting the environmental risks from arable land to, for example, wetlands. Now, algae are not as well-studied or are research workhorses such as E coli or yeast. But synthetic biology can be used to optimize and modify species growth rates, their tolerance of high cell densities, quality and quantity of the lipids produced, pathogen resistance, which would be particularly important if you're talking about using a production platform that's an open pond. But, of course, the risks and benefits are going to depend in part on that production platform, right? Open ponds have very different risks than bioreactors, or photo-bioreactors, for example. And again, we'll come back to risks and benefits and ethical issues in later videos.
