Bioreaction-separation on continuous chromatographic systems

Abstract

Combined bioreaction and separation has been carried out successfully on a simulated moving column continuous countercurrent chromatographic reactor-separator (SCCR-S) system. The continuous inversion of sucrose to glucose and fructose using invertase and the biosynthesis of dextran from sucrose in the presence of the enzyme dextransucrase have been studied.

100% sucrose conversions were achieved and product purities of up to 95% w/v were obtained in the inversion studies. The operation was carried out on a preparative scale with throughputs in excess of 16 kg of dry sugar solids per cubic metre of resin per hour used. The simultaneous inversion and product separation was found to overcome problems associated with substrate inhibition. Complete reaction and separation was obtained at feed concentrations as high as 55% w/v.

Previous studies on the biosynthesis of dextran on batch chromatographic systems showed significant improvements in product yields. The simultaneous removal of the acceptor by product fructose from the reaction mixture led to the formation of greater amounts of high molecular weight dextran (over 80% more than the conventional process at 20% w/v sucrose concentration). To carry out dextran biosynthesis on the SCCR-S system, it was necessary to repack it with larger-size resin to allow for the high pressures caused by the more viscous dextran. Complete conversions have been achieved at sucrose concentrations of 5% w/v with dextran and fructose product purities of up to 100% and 97% respectively obtained under certain conditions. Some levan formation occurred after about 50 h of operation, which is readily removed from the dextran in the normal dextran processing procedures.