ATP is not essential for cadaverine production by Escherichia coli whole-cell bioconversion

ATP plays an essential role in the substrate/product transmembrane transportation during whole-cell bioconversion. This study aimed to address the impact of ATP upon cadaverine synthesis by whole-cell biocatalysts. The results showed no significant change in the ATP content (P = 0.625), and the specific cadaverine yield (P = 0.374) was observed in enzyme-catalyzed cadaverine synthesis with exogenous addition of ATP, indicating that the enzyme-catalyzed process does not require the participation of ATP. Furthermore, a whole-cell biocatalyst co-overexpressed methionine adenosyltransferase (MetK), lysine decarboxylase (CadA), and lysine/cadaverine antiporter (CadB) was constructed and used to investigate the effect of ATP deficiency on the cadaverine production by conversion of L-methionine and L-lysine, simultaneously. The results showed no significant difference (P = 0.585) in the specific cadaverine content between high and low levels of intracellular ATP. In addition, the intra- and extracellular cadaverine concentration and the ratio of ATP/ADP of whole-cell biocatalyst were determined. Results showed that the extracellular cadaverine concentration was much higher than the intracellular concentration, and no significant changes in ATP/ADP ratio during cadaverine synthesis. In contrast, an inhibition effect of the proton motive force (PMF) inhibitor carbonyl cyanide m-chlorophenylhydrazone (CCCP) on cadaverine production was detected. These findings strongly suggest that cadaverine transport in whole-cell biocatalysts was energized by PMF rather than ATP. Finally, a model was proposed to describe cadaverine's PMF-driven transport under different external pHs during whole-cell biocatalysis. This study is the first to experimentally confirm that the cadaverine production by Escherichia coli whole-cell bioconversion is independent of intracellular ATP, which helps guide the subsequent construction of biocatalysts and optimize transformation conditions.