A two-enzyme cascade system for the bio-production of spermidine from putrescine

In vitro multiple-enzyme cascade system is becoming a promising biomanufacturing platform for producing biochemicals. Spermidine is a natural polyamine substance that is widely used in health care products and medicine. In this study, spermidine was synthesized by S-adenosylmethionine(SAM) decarboxylase and spermidine synthase through a two-enzyme cascade system in vitro. The factors influencing the efficiency of this cascade system, including the source of SAM decarboxylase, the expression conditions, the ratio of enzyme addition, reaction temperature, reaction pH, and metal ion additives were identified to determine the optimal conditions for spermidine production. With the optimized system, 3.7 g/L spermidine was finally produced from 2.5 g/L putrescine and 15 g/L SAM with the yield of 91.1 %.