Ionic liquids-based hydrolysis of Chlorella biomass for fermentable sugars

► Ionic liquids-based catalyst was used to hydrolyze algal biomass. ► The amount of HCl loading was very low, and ionic liquids could be recycled. ► High-yielding soluble sugars were obtained without the addition of enzyme, but at mild condition. ► Glucose in Chlorella biomass hydrolysate could be conversed into ethanol at high yield.