Cascade Synthesis of l-Homoserine Catalyzed by Lyophilized Whole Cells Containing Transaminase and Aldolase Activities: The Mathematical Modeling Approach

Abstract

Aldolase and transaminase coexpressed in Escherichia coli cells and lyophilized (i.e., lyophilized whole-cell biocatalyst (LWCB)) were used as biocatalysts for the one-pot cascade synthesis of l-homoserine with substrate cycling. The kinetic analysis of enzymes within lyophilized cells was performed to evaluate the behavior of the system. The best result among the performed fed-batch reactor experiments achieved was 640.8 mM (76.3 g L–1) of l-homoserine with a volume productivity of 2.6 g L–1 h–1. This is comparable with the results of the same cascade synthesis using cell-free extracts (CFEs) and significantly better than the reports in the literature applying fermentation technology. The approach applied here can serve as guidance for the design of microbial cells with an optimal ratio of expressed enzymes that act as biocatalysts in the cascade, resulting in lower biocatalyst cost, no need for the addition of expensive coenzymes, and enhanced enzyme stability as compared with cell-free extracts. ; This project has received funding from the European Union's Horizon 2020 Research and Innovation Program under Grant Agreement no. 635595 (CarbaZymes). This communication reflects only the beneficiary's view, and the European Commission is not responsible for any use that may be made of the information it contains. The authors gratefully acknowledge Prozomix Ltd. (United Kingdom) for providing the lyophilized whole cells. The authors also acknowledge the Ministerio de Ciencia e Innovación (MICIN), the Fondo Europeo de Desarrollo Regional (FEDER) (grant RTI2018-094637-B-I00), and Programación Conjunta Internacional (PCI2018-092937), through the initiative ERA CoBioTech (Tralaminol) ; Peer reviewed