Coupling the fermentation and membrane separation process for polyamides monomer cadaverine production from feedstock lysine

Abstract

Nylon is a polyamide material with excellent performance used widely in the aviation and automobile industries, and other fields. Nylon monomers such as hexamethylene diamine and other monomers are in huge demand. Therefore, in order to expand the methods of nylon production, we tried to develop alternative bio-manufacturing processes which would make a positive contribution to the nylon industry. In this study, the engineered E. coli-overexpressing Lysine decarboxylases (LDCs) were used for the bioconversion of l-lysine to cadaverine. An integrated fermentation and microfiltration (MF) process for high-level cadaverine production by E. coli was established. Concentration was increased from 87 to 263.6 g/L cadaverine after six batch coupling with a productivity of 3.65 g/L-h. The cadaverine concentration was also increased significantly from 0.43 g cadaverine/g l-lysine to 0.88 g cadaverine/g l-lysine by repeated batch fermentation. These experimental results indicate that coupling the fermentation and membrane separation process could benefit the continuous production of cadaverine at high levels.

Keywords: batch fermentation, cadaverine; lysine decarboxylases, membrane separation, polyamides monomer.

FIGURE 1

The production of DAP. l‐lysine was converted to 5t6r by the action of lysine decarboxylase

FIGURE 2

Key factors bioconversion such as substrate concentration, temperature and time of fermentation were optimized for efficient reaction. (A) The final quantity of cadaverine produced by three lysine decarboxylases fermentation (pH = 7, temperature was 30℃ and the concentration of cadaverine was 20 g/L). (B) The fermentations of 20, 40, 60, and 80 g/L l‐lysine. (pH = 7, temperature was 30℃ and fermentation time was 96 h) (C) The temperature effecting cadaverine. (pH = 7, the concentration of cadaverine was 40 g/L) (D) The concentration of cadaverine and glucose in the broth with the change of OD₆₀₀ over the course of 72 h. (pH = 7, temperature was 30℃ and the concentration of cadaverine was 90 g/L)

FIGURE 3

Device schematic of coupling the fermentation and membrane separation process

FIGURE 4

The progress of batch fermentation coupling the fermentation and membrane separation. The concentration in broth of cadaverine in six batch of membrane separation and fermentation. (pH = 7, temperature was 30℃ and time in each batch was 12 h)