An electrospun chitosan-based nanofibrous membrane reactor immobilized by the non-glycosylated rPGA for hydrolysis of pectin-rich biomass

Most native polygalacturonases are glycosylated. Owing to the influence of attached glycans on the function of proteins, an immobilized non-glycosylated polygalacturonase is fabricated for the degradation of pectin-rich biomass pectin into fermentable sugars. Recombinant non-glycosylated and glycosylated PGAs expressed by E. coli and P. pastoris, respectively, were prepared. As application model, recombinant polygalacturonases in immobilized enzyme membrane reactors were tested. The electrospun chitosan-based nanofibrous membrane was selected as the support matrix. The maximum enzyme loading efficiency and enzyme binding efficiency of non-glycosylated polygalacturonase and glycosylated polygalacturonase were 89.12 mg/g and 84.13% and 34.16 mg/g and 87.18%, respectively, suggesting that the glycosylation of polygalacturonases had a serious effect on its immobilization. The membranes were characterized by scanning electron microscope, Fourier transform infrared spectroscopy and X-ray diffraction. Furthermore, the glycosylation can significantly enhance the stability of recombinant polygalacturonases. Meanwhile, the glycosylation influenced their specific activity and degradation pattern. Most interesting of all, some d-galacturonic acid monomers occurred in the hydrolysate after the degradation of pectin by the non-glycosylated polygalacturonase, and the yield of reducing sugar could be 31.98 mg after 60min, with a conversion rate of 63.96%. Thus, the constructed reactor has potential in using pectin-rich biomass as the feedstock.