TECHNOLOGY FOCUS - BIOLOGY - Preferred Method: The hydrolysate collected in step (c) is concentrated by evaporation at below 90 degrees C in step (d). The step (d) further comprises a membrane separation step for the hydrolysate collected in step (c) to separate a portion of water from the liquid fraction. The separation step comprises separating the hydrolysate into a first portion and a second portion in step (d), where the first portion of hydrolysate is concentrated to a higher temperature of 90 degrees C, and the concentrated hydrolysate portion is mixed with the second hydrolysate portion. The step (a) is performed to recover a liquid containing sugar fraction and a solid fraction containing the pretreated substrate. The solid fraction is sent to step (b). The liquid fraction is mixed with the effluent enriched oligosaccharides from step (e). The effluent from step (e) comprises sophorose and/ or gentobiose. The microorganism comprises Trichoderma reesei. The solid/liquid separation of the effluent in the production of cellulases is carried out to recover a liquid fraction containing cellulases, and recycling the liquid fraction in the reactor of step (b). The part of the effluent output from the step (a) is sent to a simultaneous hydrolysis and fermentation unit. The fermentation comprises ethanolic fermentation to produce ethanol as the major alcohol, or butyl fermentation to produce n-butanol alone or as a mixture with acetone or isopropanol. EXAMPLE - Crude hydrolysate was filtered using a filter with a porosity of 100 mu m to separate a liquid fraction containing 12 wt.% of dry matter, a solid fraction containing 35 wt.% of dry matter, where the liquid fraction contains 75 g/l of glucose, and has a p-glucosidase activity of 6 IU/ml and a moisture content of 90 wt.%. The liquid fraction was then supplemented with 60 wt.% of glucose syrup to obtain a liquid fraction having a glucose concentration of 500 g/l and a water content of 57.5 wt.%. The mixture was incubated for 24 hours at 50 degrees C under stirring. The incubated mixture was boiled for 5 minutes to denature the enzymes and then analyzed by high-performance liquid chromatography such that the analysis indicates that the hydrolysate contained about 11 g/l of a mixture of sophorose and gentiobiose and 488 g/l of glucose (or 2.2% conversion of glucose oligosaccharides).