Engineering <i>De Novo</i> Monoethanolamine Production From Glucose in <i>Escherichia coli</i>

Energy generation from oil, gas, or coal fired power plants results in significant CO₂ emissions which are only expected to increase in the future. For such static point sources, monoethanolamine (MEA) represents an effective solvent for post combustion CO₂ capture via gas scrubbing. Meanwhile, MEA finds additional industrial uses, including in detergents, emulsifiers, polishes, pharmaceuticals, and cosmetics. Since current methods for MEA production are energy intensive and unsustainable, this study investigated the systematic engineering of Escherichia coli for direct MEA biosynthesis from glucose. First, endogenous production of precursor serine was enhanced by i) deregulating feedback inhibition at phosphoglycerate dehydrogenase, ii) deleting multiple native serine deaminases and ethanolamine-ammonia lyase to prevent degradation, and iii) optimizing the carbon/nitrogen ratio in the culture medium. Two plant-derived serine decarboxylases (from Spinacia oleracea and Arabidopsis thaliana) were then evaluated with respect to their relative heterologous activity, of which the latter displayed the greatest activity in E. coli resting cells. The final engineered strain ultimately produced up to 515 mg/L MEA in shake flasks, and up to ~2.4 g/L MEA in a benchtop fed batch bioreactor. The collective data suggest that future improvements in MEA production should be possible via continued strain engineering to enhance the supply of precursor serine.