Product removal strategy and fouling mechanism for cellulose hydrolysis in enzymatic membrane reactor

Abstract

One of the critical problems in enzymatic membrane reactor for lignocellulosic biomass conversion is the decline in the performance due to membrane fouling. In this study, cellulose hydrolysis was carried out in an enzymatic membrane reactor with different substrate concentrations (5–20 g/L) and different product removal strategies in order to investigate their effects on the fouling mechanism, membrane performance, and the product yield. The membrane flux decline was less severe in the intermittent product removal at 24 h interval than the product removal at 4 h interval. The cellulose conversion was more than 80% and the productivity of 9.1 g reducing sugar/ g cellulase was achieved. The cellulose conversion decreased from 88.48 to 61.43% with increasing substrate concentration and the flux also declined from 23.92 to 15.15 L/m2 h. The membrane surface roughness increased with increasing substrate concentration, with the highest at 38.50 nm at 20 g/L. The cake formation model was the predominant fouling mechanisms at all substrate concentrations. Our study indicates that the product removal strategies and substrate concentrations have significant impact on the separation process and membrane fouling during enzymatic hydrolysis of cellulose.