Kinetic analysis of galacto-oligosaccharides (GOS) formation from lactose in a broad range of operating parameters • Static and dynamic perturbation experiments performed to identify inhibition effects and reaction network • Catalytic cycle postulated and mechanistic kinetic models for GOS synthesis based on Christiansen methodology derived • Sensitivity analysis by parameter reduction techniques performed to reduce kinetic models to sensitive parameters only • Model validation successful, provides basis for process development and optimization

The production of prebiotics like galacto-oligosaccharides (GOS) on industrial scale is becoming more important due to increased demand. GOS are synthesized in batch reactors from bovine lactose using the cost intensive enzyme β-galactosidase (β-gal). Thus, the development of sustainable and more efficient production strategies, like enzyme immobilization in membrane reactors are a promising option. Activated methacrylatic monoliths were characterized as support for covalent immobilized β-gal to produce GOS. The macroporous monoliths act as immobilized pore-through-flow membrane reactors (PTFR) and reduce the influence of mass-transfer limitations by a dominating convective pore flow. Monolithic designs in the form of disks (0.34 mL) and for scale-up cylindric columns (1, 8 and 80 mL) in three different reactor operation configurations (semi-continuous, continuous and continuous with recirculation) were studied experimentally and compared to the free enzyme system. Kinetic data, immobilization efficiency, space-time-yield and long-term stability were determined for the immobilized enzyme. Furthermore, simulation studies were conducted to identify optimal operation conditions for further scale-up. Thus, the GOS yield could be increased by up to 60% in the immobilized PTFRs in semi-continuous operation compared to the free enzyme system. The enzyme activity and long-time stability was studied for more than nine months of intensive use.

Four different activated methacrylatic monoliths, acting as pore‐through‐flow membrane reactors in order to reduce enzyme costs and mass‐transfer limitations, were characterized as support for immobilization of β‐galactosidase to produce galacto‐oligosaccharides (GOS). GOS synthesis was studied in different operation modes. A higher affinity of the immobilized enzyme towards the transgalactosylation reaction could be obtained, which results in desired GOS with higher degree of polymerisation. Kinetic models were successfully parametrized forming a basis for process modeling and optimization.

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