A novel strategy for l-arginine production in engineered Escherichia coli

Abstract

Backgroundl-arginine is an important amino acid with applications in diverse industrial and pharmaceutical fields. n-acetylglutamate, synthesized from l-glutamate and acetyl-CoA, is a precursor of the l-arginine biosynthetic branch in microorganisms. The enzyme that produces n-acetylglutamate, n-acetylglutamate synthase, is allosterically inhibited by l-arginine. l-glutamate, as a central metabolite, provides carbon backbone for diverse biological compounds besides l-arginine. When glucose is the sole carbon source, the theoretical maximum carbon yield towards l-arginine is 96.7%, but the experimental highest yield was 51%. The gap of l-arginine yield indicates the regulation complexity of carbon flux and energy during the l-arginine biosynthesis. Besides endogenous biosynthesis, n-acetylglutamate, the key precursor of l-arginine, can be obtained by chemical acylation of l-glutamate with a high yield of 98%. To achieve high-yield production of l-arginine, we demonstrated a novel approach by directly feeding precursor n-acetylglutamate to engineered Escherichia coli.ResultsWe reported a new approach for the high yield of l-arginine production in E. coli. Gene argA encoding n-acetylglutamate synthase was deleted to disable endogenous biosynthesis of n-acetylglutamate. The feasibility of external n-acetylglutamate towards l-arginine was verified via growth assay in argA− strain. To improve l-arginine production, astA encoding arginine n-succinyltransferase, speF encoding ornithine decarboxylase, speB encoding agmatinase, and argR encoding an arginine responsive repressor protein were disrupted. Based on overexpression of argDGI, argCBH operons, encoding enzymes of the l-arginine biosynthetic pathway, ~ 4 g/L l-arginine was produced in shake flask fermentation, resulting in a yield of 0.99 mol l-arginine/mol n-acetylglutamate. This strain was further engineered for the co-production of l-arginine and pyruvate by removing genes adhE, ldhA, poxB, pflB, and aceE, encoding enzymes involved in the conversion and degradation of pyruvate. The resulting strain was shown to produce 4 g/L l-arginine and 11.3 g/L pyruvate in shake flask fermentation.ConclusionsHere, we developed a novel approach to avoid the strict regulation of l-arginine on ArgA and overcome the metabolism complexity in the l-arginine biosynthesis pathway. We achieve a high yield of l-arginine production from n-acetylglutamate in E. coli. Co-production pyruvate and l-arginine was used as an example to increase the utilization of input carbon sources.