Process for pretreatment of the lignocellulosic biomass with a hydrated inorganic salt making it possible to obtain a cellulosic fraction and a hemicellulosic fraction

Process for pretreatment of the lignocellulosic biomass comprising the following stages:

• a) A stage for acid hydrolysis of the biomass by an acid solution leading to a liquid fraction that contains the bulk of the hemicellulose in the form of products of hydrolysis and acid and to a solid fraction containing the bulk of the cellulose and the lignin,
• b) A stage for separating the solid fraction and the liquid fraction obtained in stage a),
• c) A stage for drying the solid fraction obtained in stage b),
• d) A stage for baking the dried solid fraction obtained in stage c) in the presence of or in the absence of an organic solvent, in a medium comprising at least one hydrated inorganic salt of Formula (I):
• MXn′n′H2O
• in which
• M is a metal selected from the groups 1 to 13 of the periodic table,
• X is an anion, and
• n is an integer between 1 and 6, and with
• n′ being between 0.5 and 12,
• making it possible to obtain a solid fraction and a liquid fraction containing the hydrated inorganic salt,
• e) A stage for separating the solid fraction and the liquid fraction obtained in stage d),
• f) Optionally, a stage for treatment of the solid fraction obtained in stage e),
• g) A stage for enzymatic hydrolysis of said solid fraction obtained from stage e) and/or f),
• and in which at least a portion of the liquid fraction obtained in stage b) is used for the growth of the microorganism that produces enzymes necessary for the enzymatic hydrolysis of stage g).