Metabolic engineering of Corynebacterium glutamicum for production of L-leucine and 2-ketoisocaproate

En savoir plus sur le livre

The depletion of fossil energy sources has intensified the search for sustainable production processes using renewable resources. Biotechnological methods employing microorganisms like Corynebacterium glutamicum as biocatalysts are crucial for producing valuable substances, including the branched-chain amino acids L-valine, L-isoleucine, and L-leucine, along with their keto acid precursors, which have various commercial uses in food, feed, and pharmaceuticals. This work focuses on the metabolic engineering of C. glutamicum to create efficient strains for L-leucine and 2-ketoisocaproate production. A key enzyme in L-leucine biosynthesis, the leuA-encoded 2-isopropylmalate synthase, is feedback-inhibited at low L-leucine concentrations. A feedback-resistant variant was identified in a weak L-leucine producer strain, B018, obtained through random mutagenesis. The leuA_B018 gene was integrated into the C. glutamicum genome, alongside other modifications to enhance L-leucine production, including deletions of the ltbR and iolR genes, reduction of citrate synthase activity, and introduction of a modified ilvN gene. The resulting strains were evaluated in shake flask and bioreactor cultivations, achieving L-leucine levels exceeding 24 g l-1 under fed-batch conditions. The maximum molar yield and productivity were 0.30 mol per mol glucose and 4.3 mmol l-1 h-1, respectively, demonstrating the potential for industrial application in a d