NOVELTY - Production (p1) of carbohydrate-enriched biomass involves providing lignocellulosic biomass comprising lignin; suspending the biomass in an organic solvent solution comprising water and at least one organo-mercaptan under alkaline conditions where a biomass-solvent suspension is formed; heating the biomass-solvent suspension to 100-220 degrees C for 5 minutes to 5 hours where lignin is fragmented and is dissolved in the suspension; and removing the dissolved lignin.    USE - For the production of carbohydrate-enriched biomass (claimed).    ADVANTAGE - The method is single step process using lower concentrations of sulfur and recyclable base in the form of ammonia or alkylamines as opposed to the use of alkali metal hydroxides which are not amenable to either recycle or disposal. By incorporating organo-mercaptans into the organic solvent process under alkaline conditions (due to the presence of alkali metal, alkaline earth hydroxide, ammonia and/or alkylamine), the anionic thiolate, is primed to carry out substitution reactions on the aryl ethers of the lignin. The alkaline conditions also favor the formation of quinone methides from lignin. These are also readily attacked by thiols. The presence of ammonia and/or alkylamines, in addition to raising the pH, supplements the thiol nucleophilic chemistry in attacking the lignin as well as protecting the polysaccharide against peeling reactions result in monosaccharide release and loss at high pH. The use of alkylamines and/or ammonia as bases avoids the generation of an inorganic waste stream which would otherwise add to the financial and environmental cost of the process. The organo-mercaptans also act as reducing agents, promoting the reduction of quinone methides, eliminating beta -aryl ethers as phenoxyl radicals and protecting sugar residues from oxidative reactions. The use of organo-mercaptans in the lignocellulosic biomass pretreatment process enhances the fragmentation of lignin and increases the selectivity of lignin extraction with respect to carbohydrate, producing carbohydrate-enriched biomass that is highly susceptible to enzymatic saccharification. It is also possible that thioglycolate, in substitution reactions that displace lignin aryl ethers, introduces carboxyl groups into lignin fragments, thus increasing their hydrophilicity, making them more soluble in aqueous medium and less likely to adsorb cellulolytic enzyme.    DETAILED DESCRIPTION - An INDEPENDENT CLAIM is included for simultaneous fragmentation and selective extraction (m1) of lignin from lignocellulosic biomass to produce a lignin-free biomass involving providing multi-component solvent solution (s1) comprising lignocellulosic biomass, multi-component solvent solution comprising ethanol (40-70%) in water, organo-mercaptan, and at least one alkylamine under alkaline conditions; contacting the biomass with the solution (s1) to form a solvent-biomass mixture; placing the solvent-biomass mixture in a sealed pressure vessel where the resultant mixture is heated at 100-220 degrees C for 5 minutes to 5 hours where lignin is fragmented and dissolved in the solvent; removing the dissolved lignin by filtration; and washing the residual biomass with organic solvent.