Metabolic engineering of Candida tropicalis for efficient production of 1,2,4-butanetriol

Abstract:

[Background] 1,2,4-butanetriol (BT), a chiral polyol, plays a role as a platform chemical in the synthesis of energetic materials such as 1,2,4-butanetriol trinitrate, which is used as a propellant in a variety of military applications, including aircraft, rockets, and missiles. With the rapid development of synthetic biology, building microbial cell factories for the production of 1,2,4-butanetriol has received increasing attention. [Objective] In this study, we employed metabolic engineering to optimize the exogenous 1,2,4-butanetriol synthesis pathway in a pre-constructed strain of Candida tropicalis, aiming to reduce the accumulation of intermediates and increase the production of 1,2,4-butanetriol. Furthermore, we evaluated the ability of the engineered strain to produce 1,2,4-butanetriol by fermentation with inexpensive corncob hydrolysate. [Methods] We employed promoter engineering to optimize the expression level of the xylose dehydrogenase gene and reduce the accumulation of xylonate. Furthermore, we enhanced the production of 1,2,4-butanetriol in C. tropicalis by using calcium carbonate as a neutralizer to regulate the pH and optimizing the concentration of iron ions in the fermentation medium. [Results] Through the combined efforts of metabolic engineering and fermentation process optimization, the final yield was increased by 42%, reaching 6.20 g/L in a 5 L fermenter. In addition, the engineered strain was capable of producing 2.60 g/L 1,2,4-butanetriol by using corncob hydrolysate as the substrate. [Conclusion] We improve the ability of C. tropicalis to synthesize 1,2,4-butanetriol by metabolic engineering and fermentation process optimization. Moreover, we for the first time evaluate the feasibility of C. tropicalis cell factories for the synthesis of 1,2,4-butanetriol with corncob hydrolysate, which provides support the large-scale production of 1,2,4-butanetriol by fermentation with biomass feedstocks.