Modeling-based optimal control policies for a multienzymatic system with distinct thermal stabilities in packed-bed reactors

Multienzyme systems are highly attractive for allowing a one-pot reactor configuration, but require compromise operational conditions. This work aims at a model-based productivity and economic comparison between one-pot and in-series reactor configurations under optimally controlled temperature and lactose feed-flow rate profile. The case study evaluates the sequential conversion of lactose to fructose, catalyzed by a labile β-galactosidase from Aspergillus oryzae and a highly stable glucose isomerase from Streptomyces murinus. Kinetic and thermal deactivation parameters were derived from literature available data for these biocatalyst. Considering Michaelis-Menten-type kinetics and thermal decay, the optimization aimed to maximize fructose concentration or productivity across three biocatalyst distributions. The results highlight that complex kinetics drive non-monotonic optimal temperature profiles. Furthermore, results show that for enzymes with pronounced thermal stability mismatches, the sequential configuration outperforms one-pot alternatives. When maximizing productivity, the in-series design achieved an average productivity of (Formula presented), orders of magnitude higher than the limit of (Formula presented), observed in optimized one-pot systems. When maximizing productivity under an equivalent total enzyme load of 300 g·L−1[jls-end-space/], the in-series design with individually immobilized enzymes achieved an average productivity of 2412.90 kg· h−1[jls-end-space/], orders of magnitude higher than the limit of  ∼  130 kg·h−1 observed in optimized one-pot systems utilizing a multienzyme biocatalyst. While one-pot setups increase feed flow rates to protect the labile enzyme, compartmentalization enables thermal decoupling. A techno-economic evaluation confirms that this productivity leap translates into an increase in profitability, completely offsetting the higher capital costs of the in-series configuration.