Escherichia coli BL21(DE3) Optimized Deletion Mutant as the Host for Whole Cell Biotransformation of N‑acetyl‑D‑neuraminic Acid

Abstract N‑acetyl‑D‑neuraminic acid (Neu5Ac) is the precursor for antiflu medicine Zanamivir. Chemoenzymatic synthesis of Neu5Ac involves N-acetyl-D-glucosamine 2-epimerase (AGE)-catalyzed epimerization of N-acetyl-D-glucosamine to N-acetyl-D-mannosamine (ManNAc), and aldolase-catalyzed condensation between ManNAc and pyruvate. Herein, via whole cell biotransformation system, BT0453, cloned from Bacteroides thetaiotaomicron, showed the highest biotransformation yield. Next, an optimized host was obtained by deleting the Escherichia coli BL21(DE3) chromosomal genes involved in product exportation, substrate degradation and pH change, a significant 16.5% yield improvement was observed with the host. The research highlights the importance of host’s chromosome engineering for biotransformation.