L-2-aminobutyrate is a critical chiral precursor of new drugs, which has been widely used in chemical and pharmaceutical industries. In this study, the metabolic pathway of L-threonine in Escherichia coli THRD was extended to obtain an L-2-aminobutyrate producing strain. The threonine dehydratase encoding genes ilvA2 and ilvA4 were firstly individually overexpressed in E. coli THRD. The resulting strain THRD/pTrc99a-ilvA2 produced 18 g/L L-2-ketobutyrate in a 5 L fermenter by fed-batch fermentation. Subsequently, encoding genes of tyrosine aminotransferase, glutamate dehydrogenase, and leucine dehydrogenase, tyrB, gdh, and bcdBS, respectively, were overexpressed together with ilvA2 to catalyze the conversion of L-2-ketobutyrate to L-2-aminobutyrate. The strain THRD/pTrc99a-bcdBS-ilvA2 produced 19 g/L L-2-aminobutyrate. The effects of disrupting L-threonine exporters on L-2-aminobutyrate fermentation were investigated, and the production of L-2-aminobutyrate in strain THRDΔrhtC/pTrc99a-bcdBS-ilvA2 increased to 22 g/L. Taken together, the results clearly indicated that the L-threonine producing strain could be effectively transformed into an L-2-aminobutyrate producer by extending its downstream metabolic pathway. This study lays a solid basis for constructing L-2-aminobutyrate high producing strains. This study can also be referred in other metabolic engineering studies to biosynthesize new products by pathway extension.
WANG Ting
,
HAN Chao
,
MAO Qian
,
ZHANG Dezhi
,
CAI Ningyun
,
LIU Hongliang
,
LI Yanjun
,
CHEN Ning
. Construction of Escherichia coli strain producing L-2-aminobutyrate[J]. Food and Fermentation Industries, 2019
, 45(3)
: 56
-63
.
DOI: 10.13995/j.cnki.11-1802/ts.018611
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