Development of a bacterial chassis for amine synthesis

The biocatalytic synthesis of chiral amines from carbonyl compounds and ammonia represents a major advancement in sustainable synthetic chemistry. Using whole cells for bioamination offers advantages such as low preparation cost and direct applicability; however, amine toxicity often limits these reactions when living cells are used. This thesis focuses on the generation, characterization, and biocatalytic application of amine-tolerant bacteria for sustainable, high-yielding amine synthesis. We employed adaptive laboratory evolution to generate amine-tolerant Escherichia coli strains that enabled the enantioselective reductive amination of prochiral ketones, achieving yields of up to 80% at high substrate loadings (up to 23 g L^-1), without cofactor supplementation. Additionally, the adapted strains facilitated the bioamination of alcohols with modest to good efficiency—typically outperforming non-adapted cells—and enabled the bioproduction of short-chain alkyl amines via enzymatic decarboxylation of amino acid precursors. The genomes of the amine-tolerant strains revealed a multifactorial adaptive response—primarily involving membrane modifications, stress coping, and regulatory mechanisms—that conferred cross-resistance to structurally diverse amines, likely through cell reinforcement or amine exclusion. Collectively, this thesis deepens our understanding of microbial adaptation to chemical stress and advances the development of robust whole-cell biocatalysts for amine production.