Modification of a cellulase system by engineering Penicillium oxalicum to produce cellulose nanocrystal

In this study, three endoglucanases (EGs; Cel7B, Cel5B, and Cel12A), one cellobiohydrolase (CBH), and two auxiliary proteins (swollenin: SWO1 and SWO4) were used to hydrolyze microcrystalline cellulose (MCC) for cellulose nanocrystal (CNC) preparation. The mixture experiment of the three EGs showed that high CNC yield was obtained when the ratio of Cel7B and Cel5B is 1:1.11 (protein weight). Moreover, the addition of CBH (1 mg/g) and SWO1 from Trichoderma reesei effectively increased the yield of CNC. On the basis of the results, the cellulase-producing strain of Penicillium oxalicum M12 was engineered to improve its cellulase system. An engineered strain of cEES performed well in CNC preparation. CNC with a yield of 11.79 % and a crystallinity of 83.85 % were produced using the crude enzyme from cEES as a means to hydrolyze MCC, and the size and shape of CNC were uniform and fusiform.