Method to produce water-soluble sugars from biomass using solvents containing lactones

A process to produce an aqueous solution of carbohydrates comprising C6-sugar-containing oligomers, C6-sugar monomers, C5-sugar-containing oligomers, C5-sugar monomers, or any combination thereof, the process comprising:

• (a) reacting biomass or a biomass-derived reactant with a solvent system comprising (i) an organic solvent selected from the group consisting of beta-, gamma-, and delta-lactones, and combinations thereof, and (ii) at least about 1 wt % water;
• in the presence of an acid catalyst for a time and under conditions to yield a product mixture wherein at least a portion of water-insoluble C6-sugar-containing polymers or oligomers, or water-insoluble C5-sugar-containing polymers or oligomers, if present in the biomass or biomass-derived reactant, are converted to water-soluble C6-sugar-containing oligomers, C6-sugar monomers, C5-sugar-containing oligomers, C5-sugar monomers, or any combination thereof;
• and then
• (b) adding a solute to the product mixture of step (a) in an amount sufficient to cause partitioning of the product mixture into an aqueous layer and a substantially immiscible organic layer.