Efficient synthesis 1,4-cyclohexanedicarboxaldehyde by an engineered alcohol oxidase

In this study, we selected and engineered a flavin adenine dinucleotide (FAD)-dependent alcohol oxidase (AOX) to produce 1,4-cyclohexanedicarboxaldehyde (CHDA), an initial raw material for spiral compounds, from 1,4-cyclohexanedimethanol (CHDM). First, the structure of alcohol oxidase from Arthrobacter cholorphenolicus (AcCO) was analyzed, and the mechanism of AcCO-catalyzed primary alcohol oxidation was elucidated, demonstrating that the energy barrier of the hydride (H^-) transfer (13.4 kcal·mol^-1 and 20.4 kcal·mol^-1) decreases the catalytic efficiency of the primary alcohol oxidation reaction. Therefore, we designed a protein engineering strategy to adjust the catalytically active conformation to shorten the distance of hydride (H^-) transfer and further decreased the core energy barrier. Following this strategy, variant W4 (S101A/H351V/N378S/Q329N) was obtained with 112.5-fold increased catalytic efficiency to produce CHDA compared to that of the wild-type strain. The 3 L scale preparation of CHDA reached a titer up to 29.6 g·L^-1 with a 42.2% yield by an Escherichia coli whole-cell catalyst, which demonstrates the potential of this system for industrial application.