A novel approach to the production of clinical-grade dextran

Efficient unit operations for the production and purification of the enzyme dextransucrase and the biosynthesis and fractionation of dextrans have been developed and tested. An alternative process for the production of clinical-grade dextran has been proposed by integrating these processes to achieve improved dextran product yield and the recovery of fructose as a valuable by-product. The enzyme dextransucrase, which synthesizes dextran from sucrose, has been produced either by non-aerated fed-batch or continuous fermentations, purified by continuous ultracentrifugation and ultrafiltration and used in a bioreactor-separator stage for the biosynthesis of dextran. High molecular weight dextrans have been biosynthesized on continuous counter-current chromatographic bioreactor-separator systems. Membrane filtration and size exclusion continuous chromatography were used for the fractionation of the native dextran and production of clinical-grade dextran. The advantages of the proposed process over the conventional process are related to cost reduction due to the elimination of ethanol usage and recovery, improved product quality control and the production and recovery of fructose as a by-product.