The In Silico Optimization of a Batch Reactor for D-Fructose Production Using the Cetus Process with In Situ Cofactor Quick Regeneration

Currently, D-fructose (DF) is produced through enzymatic isomerization of beta-D-glucose (DG) under disadvantageous conditions (equilibrium conversion of 50%, costly separation, etc.). Alternatively, the two-step Cetus enzymatic process became a promising approach for producing high-purity DF. First, DG is oxidized to keto-glucose (kDG) using commercial pyranose 2-oxidase (P2Ox). To avoid the fast P2Ox inactivation by the in situ produced hydrogen peroxide, catalase is added to decompose this byproduct. The DG oxidation occurs with high conversion and selectivity, leading to kDG free of allergenic aldose compounds. Then, kDG is reduced to DF by using the NADPH cofactor and aldose reductase (ALR). This study aims to evaluate the continuous in situ regeneration of NADPH at the expense of formate decomposition in the presence of formate dehydrogenase (FDH). By adopting a kinetic model from literature, this in silico analysis determines the optimal operation of a batch reactor (BR) used in the Cetus second step to maximize the DF production and minimize the consumption of costly NADPH. Compared to its simple operation, the optimized BR with cofactor regeneration reported a 25% lower NADPH consumption, though the amount of the processed substrate is ca. 3× higher. Also, the costly enzymes (ALR, FDH) consumption is 2× smaller.