NOVELTY - Producing oligosaccharides from lignocellulosic biomass comprises: (a) pretreating the biomass in reactor (1) to supply an effluent containing a pre-treated substrate; (b) carrying out an enzymatic hydrolysis of the pretreated substrate contained in the effluent in the presence of cellulases, in the reactor, to produce a hydrolysate containing glucose, cellulases and water; (c) sampling a portion, including a liquid fraction (18), of the hydrolysate from step (b); (d) reducing the water content of the portion of the hydrolysate sampled in step (c); and (e) incubating the hydrolysate.    USE - The method is useful for producing oligosaccharides including cellulases, from lignocellulosic biomass, where the cellulases are useful in the production of alcohols, organic solvents or acids (all claimed).    ADVANTAGE - The method is capable of producing oligosaccharides from inexpensive lignocellulosic biomass, which is available abundantly.    DETAILED DESCRIPTION - Producing oligosaccharides from lignocellulosic biomass comprises: (a) pretreating the biomass in reactor (1) to supply an effluent containing a pre-treated substrate; (b) carrying out an enzymatic hydrolysis of the pretreated substrate contained in the effluent in the presence of cellulases, in the reactor, to produce a hydrolysate containing glucose, cellulases and water; (c) sampling a portion, including a liquid fraction (18), of the hydrolysate from step (b); (d) reducing the water content of the portion of the hydrolysate sampled in step (c) such that the liquid fraction of the hydrolysate has a water content of less than 65 wt.% with respect to the total weight of the liquid fraction of the hydrolysate; and (e) incubating the hydrolysate from step (d) at 40-70 degrees C for a time necessary to produce an oligosaccharide-rich effluent. INDEPENDENT CLAIMS are included for:    (1) a method for producing cellulases from lignocellulosic biomass comprising producing oligosaccharides, sending a portion of the hydrolysate enriched in oligosaccharides in a reactor containing a culture medium and microorganisms capable of producing cellulases, and culturing the obtained mixture to produce an effluent enriched with cellulases; and    (2) a method for producing alcohols, organic solvents or acids comprising producing cellulases, and fermenting microorganisms to produce a fermentation broth comprising alcohol and/or solvents.    DESCRIPTION OF DRAWING(S) - The figure shows a schematic view of a method for producing oligosaccharides.    Pretreatment reactor (1)    Enzymatic hydrolysis reactor (3)    Evaporator (9)    Incubation reactor (11)    Liquid fraction. (18)