Precise measurement of decarboxylase and applied cascade enzyme for simultaneous cadaverine production with carbon dioxide recovery

Background: Bio-based nylon is synthesized from putrescine, cadaverine, or 4-amino butyric acid through decarboxylases by a green process aimed toward a renewable nylon market. Thus, quantifying the activity of the key enzyme decarboxylase with precision and efficiency, is critical for the development of the system. Moreover, one molecular carbon dioxide releasing from the reaction should be considered in greenhouse gas effect. Methods: We established a new assay based on pH value decline by using different alkaline solution to absorb and capture the CO₂ released during decarboxylation. The pH change is corresponding to decarboxylase activity. On the other hand, carbonic anhydrase (CA), phosphoribulokinase (PRK) and ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBisCo) genes involved in CO₂ respiration, were applied with lysine decarboxylase (CadA) for simultaneous production of cadaverine and recovery of CO₂. Significant Findings: The correlation between lysine, glutamate, or arginine conversion and its pH changes in different decarboxylases was successfully determined using a numerical equation with a high regression value (R² > 0.95). For cascade enzymatic reaction, RuBisCo was hardly co-expressed with CadA. Therefore, the strain with CadA and CA resulted in the release of the least amount of CO₂ among all the varieties, reaching the best CO₂ assimilation capability of −4.95 g-CO₂/g-dry cell weight (DCW) and an acceptable DAP of 15.67 g/L. This illustrates a new trend of bio-mitigation of CO₂ with simultaneous production of a variety of desirable chemicals.