NOVELTY - Producing carbohydrate-enriched biomass with high retention of hemicellulose, comprises: (a) providing lignocellulosic biomass comprising lignin, cellulose and hemicellulose; (b) suspending biomass in an organic solvent solution comprising water, ammonia and at least one nucleophile, where a biomass-solvent suspension is formed under alkaline conditions; (c) heating biomass-solvent suspension to 100-220 degrees C for 5 minutes to 5 hours; and (d) filtering free liquid under pressure after heating the suspension, where the dissolved lignin is removed.    USE - The method is useful for: producing carbohydrate-enriched biomass with high retention of hemicellulose; simultaneous fragmentation and selective extraction of lignin from lignocellulosic biomass to produce a substantially lignin-free biomass, where the biomass is switchgrass, waste paper, sludge from paper manufacture, corn fiber, corn cobs, corn husks, corn stover, grasses, wheat, wheat straw, hay, barley, barley straw, rice straw, sugar cane bagasse, sugar cane straw, yellow poplar, Sorghum, soy, and/or components obtained from processing of grains, trees, branches, roots, leaves, wood chips, sawdust, shrubs and bushes, vegetables, fruits, flowers or animal manure (all claimed); selectively extracting lignin from lignocellulosic biomass; and producing target products (e.g. value-added chemicals and fuels) from the carbohydrate-enriched biomass.    ADVANTAGE - The method: is cost-effective and highly selective; maintains the high concentrations of hemicellulose content of the biomass; provides readily saccharifiable carbohydrate-enriched biomass that is highly susceptible to enzymatic saccharification, high yields of fermentable sugars (glucose and xylose) and high yields of target products (e.g. value-added chemicals and fuels) after fermentation; provides improved lignin fragmentation, extraction and high carbohydrate retention (hemicellulose); enhances the subsequent enzymatic saccharification step; minimizes the loss of carbohydrate during the pretreatment process and maximizes the yield of solubilized sugars in saccharification; prevents polysaccharide peeling under alkaline conditions; and reduces the hydrolysis of hemicellulose and renders insoluble xylose oligomers.    DETAILED DESCRIPTION - Producing carbohydrate-enriched biomass with high retention of hemicellulose, comprises: (a) providing lignocellulosic biomass comprising lignin, cellulose and hemicellulose; (b) suspending the biomass in an organic solvent solution comprising water, ammonia in an amount of 2-20% relative to weight of dry biomass and at least one nucleophile, where a biomass-solvent suspension is formed under alkaline conditions; (c) heating biomass-solvent suspension to 100-220 degrees C for 5 minutes to 5 hours, where lignin is fragmented and dissolved in the suspension; and (d) filtering free liquid under pressure after heating the suspension, where the dissolved lignin is removed. An INDEPENDENT CLAIM is also included for simultaneous fragmentation and selective extraction of lignin from lignocellulosic biomass to produce a substantially lignin-free biomass, comprising: providing an amount of lignocellulosic biomass containing lignin and carbohydrate, a multi-component solvent solution comprising 40-70% ethanol in water, ammonia in an amount of 2-20%, and the nucleophile; contacting the biomass with the multi-component solvent solution to form a solvent-biomass mixture; placing the solvent-biomass mixture in a sealed pressure vessel, where the mixture is heated at 100-220 degrees C for 5 minutes to 5 hours, and lignin is fragmented and dissolved in the solvent; removing the dissolved lignin by filtration; and washing the residual with organic solvent, where substantially lignin-free biomass is produced.