PROCESS FOR PRODUCING BIOETHANOL BY ENZYMATIC HYDROLYSIS OF CELLULOSE

The invention concerns a process for producing bioethanol comprising the steps of pretreatment (consisting in destructuring the lignocellulosic vegetable raw material by placing it in the presence of a mixture containing formic acid， acetic acid and water， then in separating cellulose)， of enzymatic hydrolysis and of alcoholic fermentation， characterized in that it comprises， prior to the enzymatic hydrolysis， a step of partial elimination of the lignins so as to obtain a residual overall level of lignins (T)， expressed as percentage by weight， which is non-zero and which is included in a range determined by a lower limit， and an upper limit Bsup， respectively equal to 0.30% and 4%. In order to obtain conditions of acidification before the enzymatic hydrolysis step， the process comprises a step for re- acidification of the mixture， which is carried out by means of an acid， or of a mixture of acids， of determined pKa， and in particular by means of weak organic acids such as acetic acid and/or formic acid. The invention concerns a process for producing bioethanol comprising the steps of pretreatment (consisting in destructuring the lignocellulosic vegetable raw material by placing it in the presence of a mixture containing formic acid， acetic acid and water， then in separating cellulose)， of enzymatic hydrolysis and of alcoholic fermentation， characterized in that it comprises， prior to the enzymatic hydrolysis， a step of partial elimination of the lignins so as to obtain a residual overall level of lignins (T)， expressed as percentage by weight， which is non-zero and which is included in a range determined by a lower limit， and an upper limit Bsup， respectively equal to 0.30% and 4%. In order to obtain conditions of acidification before the enzymatic hydrolysis step， the process comprises a step for re- acidification of the mixture， which is carried out by means of an acid， or of a mixture of acids， of determined pKa， and in particular by means of weak organic acids such as acetic acid and/or formic acid.