The present invention concerns a production of liquefied lignocellulosic substrate by enzymatic reaction. 10% to 40% by weight dry matter of pre-treated lignocellulosic substrate is contacted, with water and enzymes at 0.1 to 60 mg of enzymes per gram of cellulose for a period of 1 to 24 hours. Over time, at least the value of one of the rheological characteristics of the reaction medium is measured. If a reduction of the value is detected over time, the following step a) is carried out: a) the feeding flow rate of pre-treated lignocellulosic substrate is increased, with or without modification of the flow rate of enzymes and/or water; If an increase of the value is detected over time, a step b) is carried out: b) the feeding flow rate of water and/or enzymes is increased, with or without modification of the flow rate of pre-treated lignocellulosic substrate.