The ion transporter endows ion- and pH-homeostasis enhancing L-arginine synthesis in Corynebacterium crenatum

Abstract:

L-arginine is a semi-essential amino acid that is widely used in food, pharmacy and feed industries. In recent years, the metabolic engineering of L-arginine producing strains is rarely involved in the field of ion transport. [Objective] In this study, we found that adding appropriate K⁺ in the medium was beneficial to Corynebacterium crenatum SYPA5-5 to increase L-arginine production. [Methods] Transcriptome of C. crenatum SYPA5-5 was analyzed under the concentrations of 0.5 g/L and 2.5 g/L K₃PO₄. We selected significant monovalent cation/H⁺ antiporter Mrp1A and cation transport ATPase CTAP1 to investigate the relation among K⁺ transport, growth and L-arginine synthesis in C. crenatum SYPA5-5. [Results] The genes mrp1 and ctap1 were deleted and overexpressed to analyze their effects on the production of L-arginine in C. crenatum SYPA5-5. The overexpression of Mrp1A and CTAP1 was beneficial to ion homeostasis, pH tolerance and osmoregulation, ultimately increasing L-arginine production. In fed-batch fermentation, L-arginine production of 5-5(mrp1), 5-5(ctap1) and 5-5(mrp1ctap1) strains reached 61.4 g/L, 63.9 g/L and 65.3 g/L. The yield reached 0.383, 0.392 and 0.395 g/g, which were 34.9%, 38.0% and 39.1% increase compared with C. crenatum SYPA5-5, respectively. [Conclusions] The CTAP1 is K⁺ transporter that can transport K⁺ from extracellular to intracellular. Meanwhile, the Mrp1A can transport K⁺ and Na⁺ to the extracellular, and the extracellular H⁺ was transported into the cell, thus maintaining the intracellular pH stability. The study of Mrp1A and CTAP1 provide a foundation for understanding the relationship between ion transport mechanisms and L-arginine synthesis.

Key words:Corynebacterium crenatum SYPA5-5;cation transport ATPase CTAP1;monovalent cation/H⁺ antiporter Mrp1A;K⁺