Steam explosion is a thermo-mechaticochemical Pretreatment which allows the breakdown oflighocellulosic structural components by the action of heating, formation of organic acids during the process, and shearing forces resulting in the,expansion of the moiSture. Two distinct stages,compose the steam explosion process: vapocracking and explosive decompression, which include modification of the material components: hydrolysis of hemitellulosic components (mono- and oligosaccharide released), modification of the chemical structure of lignin, and modification of the cellulose crystallinity index, etc. These effects allow the opening of lignocellulosic structures and influence the enzymatic hydrolysis yield of the material.