Enzymatic hydrolysis of oil palm empty fruit bunch using membrane reactor

Abstract

Enzymatic hydrolysis of oil palm empty fruit bunch (EFB) was performed in a membrane reactor system. The reactor was incorporated with polyethersulfone (PES) ultrafiltration membrane to increase the cellulose conversion and reduce enzyme dosage. Parameters such as enzyme and substrate loading, transmembrane pressure (TMP) and cross-flow velocity (CFV) were investigated on the filtration flux behaviour and retention characteristics during filtration process. The cellulase enzyme was completely retained as the rejection was above 98 % for all cases and complete transmission of sugar molecules was achieved when polyethersulfone membranes with molecular weight cut-off (MWCO) of 10 kDa was used. Results on hydrodynamic parameters show that the permeate flux increased with increasing TMP and CFV. However, the enzyme and reducing sugar rejection remain fairly constant. The concentration polarisation (up to 75 % of total resistances) was the main factor that contributed to the flux decline followed by cake layer and membrane pores resistances. Cellulase was tested for its reusability up to 216 h in enzymatic membrane reactor. Productivity increased remarkably from 0.003 to 0.01 g reducing sugars/FPU enzyme in batch reactor and enzymatic membrane reactor. These results demonstrate the potential of using coupled enzymatic reactor and membrane separations for the production of reducing sugars and enzyme recovery in EFB hydrolysis.