High-Level Conversion of l-lysine into Cadaverine by Escherichia coli Whole Cell Biocatalyst Expressing Hafnia alvei l-lysine Decarboxylase

Abstract

Cadaverine is a C5 diamine monomer used for the production of bio-based polyamide 510. Cadaverine is produced by the decarboxylation of l-lysine using a lysine decarboxylase (LDC). In this study, we developed recombinant Escherichia coli strains for the expression of LDC from Hafnia alvei. The resulting recombinant XBHaLDC strain was used as a whole cell biocatalyst for the high-level bioconversion of l-lysine into cadaverine without the supplementation of isopropyl β-d-1-thiogalactopyranoside (IPTG) for the induction of protein expression and pyridoxal phosphate (PLP), a key cofactor for an LDC reaction. The comparison of results from enzyme characterization of E. coli and H. alvei LDC revealed that H. alvei LDC exhibited greater bioconversion ability than E. coli LDC due to higher levels of protein expression in all cellular fractions and a higher specific activity at 37 °C (1825 U/mg protein > 1003 U/mg protein). The recombinant XBHaLDC and XBEcLDC strains were constructed for the high-level production of cadaverine. Recombinant XBHaLDC produced a 1.3-fold higher titer of cadaverine (6.1 g/L) than the XBEcLDC strain (4.8 g/L) from 10 g/L of l-lysine. Furthermore, XBHaLDC, concentrated to an optical density (OD600) of 50, efficiently produced 136 g/L of cadaverine from 200 g/L of l-lysine (97% molar yield) via an IPTG- and PLP-free whole cell bioconversion reaction. Cadaverine synthesized via a whole cell biocatalyst reaction using XBHaLDC was purified to polymer grade, and purified cadaverine was successfully used for the synthesis of polyamide 510. In conclusion, an IPTG- and PLP-free whole cell bioconversion process of l-lysine into cadaverine, using recombinant XBHaLDC, was successfully utilized for the production of bio-based polyamide 510, which has physical and thermal properties similar to polyamide 510 synthesized from chemical-grade cadaverine.