Journal
METABOLIC ENGINEERING
Volume 54, Issue -, Pages 244-254Publisher
ACADEMIC PRESS INC ELSEVIER SCIENCE
DOI: 10.1016/j.ymben.2019.04.012
Keywords
L-aspartate; beta-alanine; Escherichia coli; Cofactor self-sufficient system; High stoichiometric yield; Platform chemical
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Funding
- Key Research Program of the Chinese Academy of Sciences [ZDRW-ZS-2016-3-1]
- National Natural Science Foundation of China [31670051]
- Edanz Group China
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L-aspartate is an important 4-carbon platform compound that can be used as the precursor of numerous chemical products. The bioproduction of L-aspartate directly from biomass resources is expected to provide a more cost-competitive technique route. Yet little metabolic engineering work on this matter has been carried out. In this study, we designed a shortcut pathway of L-aspartate biosynthesis in Escherichia coll., with a maximized stoichiometric yield of 2 mol/mol glucose. L-aspartate aminotransferase (AspC) was overexpressed for producing L-aspartate and coexpressed with L-aspartate-a-decarboxylase (PanD) for producing L-aspartate's derivative beta-alanine. L-aspartate could only be detected after directing carbon flux towards oxaloacetate and blocking the futile cycle with TCA cycle. A cofactor self-sufficient system successfully improved the efficiency of AspC-catalyzing L-aspartate biosynthesis reaction, and the glucose uptake remolding capably decreased byproducts from pyruvate. More targets were modified for relieving the bottleneck during fed-batch bioconversion. As a result, 1.01 mol L-aspartate/mol glucose and 1.52 mol beta-alanine/mol glucose were produced in corresponding strains respectively. Fed-batch bioconversion allowed 249 mM (33.1 g/L) L-aspartate or 424 mM (37.7 g/L) beta-alanine production, respectively. The study provides a novel promising metabolic engineering route for the production of L-aspartate and its derivate chemicals using biomass resources. These results also represent the first report of the efficient bioproduction of L-aspartate directly from glucose in E. coll. and the highest yield of beta-alanine reported so far.
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