NOVELTY - A process which comprises: (A) treating lignocellulosic biomass according to a first pretreatment protocol, thus generating a first product mixture; (B) separating the first product mixture into a first fractions; and (C) treating at least one fraction of the first fractions according to a second pretreatment protocol, thus generating a second product mixture    USE - The process is useful for pre-treating lignocellulosic biomass (claimed).    ADVANTAGE - The present invention provides recovery of hemicellulose and cellulose carbohydrate fractions in a sequence that keeps materials of construction to a minimum by addition of no external chemicals; minimizing the presence of inhibitory degradation products which maximizes fermentation efficiency; and bypassing the technical challenges associated with feeding lignocellulosic materials to a high-pressure pretreatment device.    DETAILED DESCRIPTION - A process which comprises:    (A) treating lignocellulosic biomass according to a first pretreatment protocol, thus generating a first product mixture;    (B) separating the first product mixture into a first fractions; and    (C) treating at least one fraction of the first fractions according to a second pretreatment protocol, thus generating a second product mixture.    The lignocellulosic biomass is grass, switch grass, cord grass, rye grass, reed canary grass, miscanthus, sugar-processing residues, sugarcane bagasse, agricultural wastes, rice straw, rice hulls, barley straw, corn cobs, cereal straw, wheat straw, canola straw, oat straw, oat hulls, corn fiber, stover, soybean stover, corn stover, forestry wastes, recycled wood pulp fiber, paper sludge, sawdust, hardwood, softwood, or their combinations; where the first pretreatment protocol comprises heating the lignocellulosic materials to a first temperature in a solution of acid for a first period of time, and where the first pretreatment protocol comprises heating the lignocellulosic materials at 100-140 degrees C in a solution of 2-5% sulfuric acid for 30-90 minutes; where the separation into a first fractions comprises washing to remove a liquids fraction, thus leaving a solids fraction; where the second pretreatment protocol comprises heating the solids fraction to a second temperature for a second period of time, and where the second pretreatment protocol comprises heating the solids fraction at 160-220 degrees C; where the liquids fraction is further processed; and where the second product mixture is further processed.