Biovalorization of Lignin-Derived Substrates to Vanillylamine via a Self-Sufficient Amino Donor and Cofactor Recycling Whole-Cell Platform.

Abstract

Lignin valorization through bioconversion to high-value chemicals is crucial for sustainable bioprocessing. Vanillin (VN), a primary lignin derivative, can be transaminated into vanillylamine (VM), a key precursor for capsaicin and pharmaceuticals. This study established a novel self-sufficient redox-complementary whole-cell system, facilitating the recycling of L-alanine and cofactors for efficient VM biosynthesis. Ammonium formate (AF) was employed as amino donor and co-substrate. Recombinant E. coli strain, co-expressing ω-transaminase (CvTA), L-alanine dehydrogenase (ALD), and formate dehydrogenase (FDH), showed higher yield in shorter reaction time compared to the strain expressing only CvTA and ALD. Intermittent feeding strategy was developed to mitigate VN cytotoxicity problem and a remarkable yield of 97.3±1.0% was achieved of VM from 60 mM VN under optimized biotransamination conditions (37ºC, pH 8.0, VN:AF=1:5, and 1.5 mM NAD⁺). Notably, a double-plasmid E. coli recombinant harboring CvTA, ALD, FDH, and aromatic dioxygenase (ADO) was constructed to convert isoeugenol into VM with a 73.2±1.1% yield. This efficient biotransamination platform not only offers a sustainable route to VM for capsaicin production but also promotes lignin valorization for a greener bioeconomy.