Enhancing pH stability of lysine decarboxylase via rational engineering and its application in cadaverine industrial production

Cadaverine, an important C5 platform compound, is the raw material of polyamides. Under a carbon neutral context, cadaverine bio-production using lysine decarboxylase as a catalyst from the sustainable resource L-lysine is more attractive than chemical synthesis from fossil resources because it is environmentally-friendly and highly efficient. However, the alkaline conditions caused by accumulation of cadaverine decreases lysine decarboxylase activity, which limits its industrial applications. Herein, we aimed to improve cadaverine enzymatic production via enhancing stability of lysine decarboxylase from Escherichia coli (EcCadA) under alkaline pH by rational engineering. Mutations of interfacial disulfide bonds between subunits in the EcCadA decamer, M1 (L89C/L442C), M2 (F102C/L547C), and M3 (V12C/D41C) were chosen. M3 exhibited a 6-fold increase in cadaverine production at pH 10.0. Non-reduced SDS-PAGE analysis demonstrated that the proportion of decamers was greatly increased compared to wild-type enzyme. In addition, molecular dynamics simulations showed that the distance between subunits increased with increased pH, especially in region B. Finally, the fed-batch bioconversion of cadaverine from L-lysine in a 5 L fermenter using M3 by whole-cell catalysis led to 418 g/L cadaverine, which is the highest titer produced to date. This study provided a more efficient enzyme to industrially produce cadaverine with reduced acid use.