Two main reasons are that the energy sector and research have their eyes on the algae.
On the one hand their high content of carbohydrates in biomass is an interesting and secondly they do not compete with crops for water or land. Unfortunately, the primary constituent algae carbohydrates, known as alginate, is not directly metabolized by bacteria. This barrier has made the biofuel produced from algae too expensive to compete with petroleum fuels.
Using synthetic biology and engineering of enzymes, Adam Wargacki and his colleagues have modified E. coli so that it produces enzymes that digest the carbohydrate polymers of algae. The bacteria thus created also manufactures membrane proteins that can transport sugars degraded form of mono and oligosaccharides and metabolic pathways that ferment sugars into the ethanol.
If this process can be scaled up, the algae could one day help meet the demand for sustainable fuel.