Autophagy and alternative fuels biotechnology: microalga are potential source for alternative biofuels. Interestingly, some alga such as the green microalga Auxenochlorella protothecoides can transition from heterotrophic to autotrophic growth in presence of limited nitrogen but abundant sugar. Under such conditions, A. protothecoides grows rapidly and accumulates large amount of lipids (>50% of the cells dry weight). This particular biomass can be harnessed for the production of biofuel and represents a more viable alternative as compared to higher plants. Manipulating autophagy in such organisms has the potential of increasing the lipid content of the cells and quantitatively improve the biofuel yield.