Production, fractionation and purification of galacto-oligosaccharides from whey lactose.

摘要

The following study aimed to optimize the production, fractionation and purification of galacto-oligosaccharides (GOSs) from whey lactose. Also, a market analysis was done to determine whether the GOS end product would be competitive in the prebiotic market. The first phase of the study involved optimization of GOS production from beta-galactosidase treatment of lactose. These optimized conditions were then applied to develop equivalent ultrafiltration (UF) free-enzyme and immobilized-enzyme systems. The effects of fluid pressure on enzyme performance were studied for the OF free-enzyme systems. In immobilized-enzyme systems, the effects of immobilizing agents on enzyme performance were studied. The two systems were made equivalent based on enzyme activity and compared as recycle-batch and continuous systems. The effect of residual monosaccharides on GOS production was also studied. In phase 2 of this study, model sugar solutions were investigated under various nanofiltration (NF) temperature, pressure, pH and concentration conditions for maximal mono-/disaccharide removal and minimal oligosaccharide loss. Optimum conditions were then applied to develop a NF diafiltration process to fractionate GOSs from the monosaccharides and lactose contained in the enzymatic sugar mixture. In phase 3 of the study, oligosaccharide model solutions were applied to ion exclusion chromatography (IEC) columns using high performance liquid chromatography (HPLC). Model solutions were studied at various flow rates, column temperatures and particle sizes to determine optimal resolution. These optimal conditions were then used to separate individual GOSs contained within the GOS fractionate from phase 2. Finally, the overall process and final product were studied for process economics and marketability. A continuous OF free-enzyme system with 42.3 U/ML of initial enzyme and 270 g/L of initial lactose was determined to achieve optimal GOS production, with relatively high maximum GOS yields (22%) and product throughput (∼140 g/h) within relatively short start-up time (15 min). Fluid pressures did not inactivate enzymes in OF free-enzyme systems, while immobilizing agents severely inactivated enzymes within immobilized systems (50-90% inactivation). During the NF GOS fractionation phase, pH and concentration showed the strongest effect on sugar retention. (Abstract shortened by UMI.)