Multiplex modification of Escherichia coli for enhanced β-alanine biosynthesis through metabolic engineering.

β-Alanine is the only naturally occurring β-amino acid, widely used in the fine chemical and pharmaceutical fields. In this study, metabolic design strategies were attempted in Escherichia coli W3110 for enhancing β-alanine biosynthesis. Specifically, heterologous L-aspartate-α-decarboxylase was used, the aspartate kinase I and III involved in competitive pathways were down-regulated, the β-alanine uptake system was disrupted, the phosphoenolpyruvate carboxylase was overexpressed, and the isocitrate lyase repressor repressing glyoxylate cycle shunt was delete, the glucose uptake system was modified, and the regeneration of amino donor was up-regulated. On this basis, a plasmid harboring the heterologous panD and aspB was constructed. The resultant strain ALA17/pTrc99a-panD-aspB could yield 4.20 g/L β-alanine in shake flask and 43.94 g/L β-alanine (a yield of 0.20 g/g glucose) in 5-L bioreactor via fed-batch cultivation. These modification strategies were proved effective and the constructed β-alanine producer was a promising microbial cell factory for industrial production of β-alanine.