Enhancing the production of S-adenosyl-L-methionine in Pichia pastoris GS115 by metabolic engineering

S-adenosyl-L-methionine is an important bioactive molecule participating in a number of biochemical reactions including the transmethylation and transsulphuration reactions of proteins and the biosynthesis of aliphatic polyamines. Strategies of metabolic engineering were used to alter the metabolic flux for enhancing the production of S-adenosyl-L-methionine (SAM) in Pichia pastoris GS115. These strategies include the over-expression of Sam 2 by knock-in technique and the disruption of Cbs by knock-out technique. Three strains, ZJGSU1 with knock- in of Sam 2, ZJGSU2 with knock-out of Cbs and ZJGSU3 with both knock-in of Sam 2 and knock -out of Cbs, were constructed for the effective production of SAM. Yields of SAM in strains ZJGSU1 and ZJGSU2 were 32- and 5-fold higher than in the original strain P. pastoris GS115, respectively. The strain ZJGSU3 had a dramatic increase in the SAM yield, and it was 46-fold higher compared to the original strain. These results indicate that there is a strong synergistic effect on the production of SAM by combining knock-in with knock-out techniques. The yield of SAM in ZJGSU3 strain was 4.37 g/L in a 3 L fermentor. This study provides deep insight into the effective industrial production of SAM in future.