Production of Putrescine in Metabolic Engineering Corynebacterium crenatum by Mixed Sugar Fermentation

Putrescine, a biogenic diamine, serves as an important component in various polyamides, medicine, and surfactants. One challenge for efficient putrescine production is to construct high-efficiency microbial cells. In this study, we designed the metabolic engineering strategies to significantly enhance the putrescine titer in Corynebacterium crenatum SYPA. First, an optimal synthetic pathway of putrescine comprising arginine decarboxylase (speA) and agmatinase (speB) genes from Escherichia coli was selected and introduced into C. crenatum. For efficient production of putrescine, the expression of agmatinase was optimized through a ribosome binding site regulation strategy. Next, the putrescine yield was furthermore increased by the knockout of snaA, speE, and cgmR to block putrescine degradation and overexpression of exporter CgmA. Additionally, the xylose utilization pathway was constructed for putrescine synthesis. Finally, the titer of putrescine was 41.5, 36.8, and 33.4 g/L from glucose, mixed sugar, and simulated wheat straw hydrolysates by fed-batch culture for 72 h, respectively. The yield was 0.18 g/g glucose, 0.15 g/g sugar, and 0.14 g/g sugar, respectively. To our knowledge, those results were the highest putrescine titers ever reported in the engineering of C. crenatum and Corynebacterium glutamicum. The engineering strains had the potential to produce putrescine from biomass hydrolysates.