Multi-membrane integrated ultrafiltration process for fractionation and purification of low molecular-weight dextrans from acidic hydrolysate

Traditional separation can hardly provide low-molecular-weight (LMW) dextrans with a narrow molecular weight distribution (polydispersity index ≤ 1.4) for pharma-industry. This study revealed the challenges of fine separation of LMW dextrans using membrane technology by investigating the influences of fouling on dextran’s penetrating pattern across the membrane using a model system with pre−depositing dextran. Subsequently, a control strategy was used to develop a cascade membrane process for high-efficient separation. The formation of a gel layer from retained dextran altered the rejection of different molecules. This issue was addressed by to regulating fouling with diafiltration, thereby enhancing separation efficiency and accuracy. Ultimately, the membrane cascade system with M1/M2/M5 successfully separated the industrial acidic hydrolysate in 3 fractions (at 2 bar), in which the 6.3-kDa fraction reached a MW distribution of 1.4 with recovery >90 %. This process enables precise MW control, demonstrating scalable production of high-purity dextrans aligned with pharmacopeial standards.