Characterization and Immobilization of a High Activity Lysine Decarboxylase from Serratia Proteamaculans NJ303 for...

Cadaverine, an essential precursor for bio-based nylon PA5X production, has emerged as a highly valuable compound in the engineered plastics and synthetic fibers industry. Current industrial biomanufacturing of cadaverine depends critically on the enzymatic activity of L-lysine decarboxylase (LDC). In this investigation, we systematically evaluated ten LDC variants originating from six distinct bacterial species, all cloned and expressed in Escherichia coli BL21(DE3). Comprehensive characterization identified SpLDC from Serratia proteamaculans as the most promising candidate, demonstrating exceptional catalytic activity under alkaline conditions. Enzymatic analysis showed that SpLDC established optimal activity at pH 6.5 and 52 °C, with remarkable stability maintained between pH 5.5-8.0 and temperatures of 37-52 °C during prolonged 12-hour incubations. Kinetic studies revealed favorable catalytic parameters (K_m = 11.5 mM, V_max = 1000 U/mg), indicating efficient substrate conversion. To enhance industrial applicability, we developed an immobilized enzyme system by genetically fusing SpLDC with a chitin-binding domain (ChBD) and subsequently immobilizing it on chitin supports. This engineered biocatalyst demonstrated superior performance compared to whole-cell systems, achieving a 3.4-fold enhancement in cadaverine production efficiency. The immobilized preparation exhibited excellent operational stability, retaining over 50% of its initial activity through ten repeated reaction cycles. This work establishes an efficient, stable, and reusable enzymatic platform for cadaverine biosynthesis, offering significant potential for sustainable nylon PA5X production at industrial scales.