Hydrolysis of Chlorella biomass for fermentable sugars in the presence of HCl and MgCl2

► HCl and MgCl2 as synergic catalyst. ► Synergic chemical hydrolysis of Chlorella biomass to produce more fermentable sugars. ► The sugar recovery with mixed HCl/MgCl2 catalyst was more than the sum of that with HCl or MgCl2 as single catalyst, respectively. ► Glucose in Chlorella biomass hydrolysate could be conversed into ethanol at high yield.