Characterization of a new lysine decarboxylase from Aliivibrio salmonicida for cadaverine production at alkaline pH

Lysine decarboxylases (LDCs) catalyze the conversion of l-lysine to cadaverine, a highly attractive building block for bio-based polyamides. Due to economic and environmental concerns, LDCs active at elevated pH are highly desirable. In this study, a new LDC from Aliivibrio salmonicida (AsLdc) was discovered, expressed, and characterized. Compared to the LDCs from Escherichia coli, LdcC and CadA, the latter was frequently used for cadaverine production, the purified AsLdc showed much higher activities at alkaline pH 7.0–8.5, for instance, 205.1 U/mg at pH 7.5 with 10 μg/mL enzyme, in comparison to 68.3 and 51.5 U/mg for CadA and LdcC, respectively. The activities of AsLdc and CadA correlated well with the proportions of decamers at the pH range of 5.0–8.5. AsLdc with a melting temperature of 79 °C was more thermostable than CadA (73.6 °C). When used for whole-cell biotransformation of l-lysine to cadaverine at pH 7.5, AsLdc completed the transformation within 7 h while the CadA did only 82.8%. These results indicate the high potential of the new AsLdc for the industrial production of cadaverine.