Development of a membrane bioreactor for enzymatic hydrolysis of cellulose

Cellulose hydrolysis is an important step in the production of bioethanol from lignocellulose. Using enzymes, as a biocatalyst, is expected to have a lower utility cost compared to the conventional acidic hydrolysis because it is carried out at milder conditions and does not require subsequent treatment step. The major obstacle to the practical realization of the potentials of enzymatic hydrolysis is the high cost of the enzymes and the slow reaction rate due to the inhibition of the enzyme by the products. In this work, a membrane bioreactor was simulated to tackle these two obstacles and enhance the reaction rate. It was found that for a 5000 kg h−1 lignocellulosic feed, to achieve 50% hydrolysis conversion, a 125 m3 membrane bioreactor containing 923 kg m−3 cellulase need to be used. The amount of the enzyme that escapes from the system and needs replacement was estimated at 92 kg h−1. The membrane reactor model was further tested using the competitive product inhibition model for the hydrolysis of totally amorphous Carboxymethylcellulose (CMC). It was shown that the reactor volume required to achieve a conversion of 50% was significantly less than that required for the lignocelluloses, even at a lower membrane mass transfer coefficient.