An environmentally friendly strategy for cadaverine bio-production: in situ utilization of CO2 self-released from L-lysine decarboxylation for pH control

Abstract

In this study, we propose a novel in situ pH control method for bio-production of cadaverine. The CO2 released from l-lysine decarboxylation in whole cell catalysis process was used to adjust the pH of the conversion system via sealing the reactor. The results showed that the self-released CO2 can well control the pH of the conversion system below 7.5 in the whole process, when the pressure of a reactor was maintained at 0.2 Mpa. Meanwhile, the system using self-released CO2 as pH control possess better ability of cadaverine production with less cell damage, compared with that of using HCl. The optimal conditions for cadaverine production using self-released CO2 as pH control were an initial concentration of l-lysine of 300.0 g/L, pyridoxal-5-phosphate of 0.15 mM, rotation of 300 rpm, time of 180 min, and resulting cadaverine of 208.2 g/L with 99.33 % conversion ratio of the substrate l-lysine. Furthermore, the protocol can be scaled up to a 3000 L reactor with similar yield and shorter conversion time (120 min) under optimized conditions, compared with that (180 min) of 7.5 L fermenter. Additionally, cadaverine of high purity (99.82 %) with recovery of 72.29 % was obtained by purification. This new approach provided a green and efficient method for industrial bio-production of cadaverine without the use of acids or other environmentally unfriendly reagents.