Cascaded valorization of brown seaweed to produce L-lysine and value-added products using Corynebacterium glutamicum streamlined by systems metabolic engineering

Sarah Lisa Hoffmann, Michael Kohlstedt, Lukas Jungmann, Michael Hutter, Ignacio Poblete-Castro, Judith Becker, Christoph Wittmann

Research output: Contribution to journalArticlepeer-review


Seaweeds emerge as promising third-generation renewable for sustainable bioproduction. In the present work, we valorized brown seaweed to produce L-lysine, the world's leading feed amino acid, using Corynebacterium glutamicum, which was streamlined by systems metabolic engineering. The mutant C. glutamicum SEA-1 served as a starting point for development because it produced small amounts of L-lysine from mannitol, a major seaweed sugar, because of the deletion of its arabitol repressor AtlR and its engineered L-lysine pathway. Starting from SEA-1, we systematically optimized the microbe to redirect excess NADH, formed on the sugar alcohol, towards NADPH, required for L-lysine synthesis. The mannitol dehydrogenase variant MtlD D75A, inspired by 3D protein homology modelling, partly generated NADPH during the oxidation of mannitol to fructose, leading to a 70% increased L-lysine yield in strain SEA-2C. Several rounds of strain engineering further increased NADPH supply and L-lysine production. The best strain, SEA-7, overexpressed the membrane-bound transhydrogenase pntAB together with codon-optimized gapN, encoding NADPH-dependent glyceraldehyde 3-phosphate dehydrogenase, and mak, encoding fructokinase. In a fed-batch process, SEA-7 produced 76 g L−1 L-lysine from mannitol at a yield of 0.26 mol mol−1 and a maximum productivity of 2.1 g L−1 h−1. Finally, SEA-7 was integrated into seaweed valorization cascades. Aqua-cultured Laminaria digitata, a major seaweed for commercial alginate, was extracted and hydrolyzed enzymatically, followed by recovery and clean-up of pure alginate gum. The residual sugar-based mixture was converted to L-lysine at a yield of 0.27 C-mol C-mol−1 using SEA-7. Second, stems of the wild-harvested seaweed Durvillaea antarctica, obtained as waste during commercial processing of the blades for human consumption, were extracted using acid treatment. Fermentation of the hydrolysate using SEA-7 provided L-lysine at a yield of 0.40 C-mol C-mol−1. Our findings enable improvement of the efficiency of seaweed biorefineries using tailor-made C. glutamicum strains.

Original languageEnglish
Pages (from-to)293-307
Number of pages15
JournalMetabolic Engineering
Publication statusPublished - Sep 2021


  • Fructokinase
  • Fructose
  • Glyceraldehyde 3-phosphate dehydrogenase
  • L-lysine
  • Macro algae
  • Mannitol 2-dehydrogenase
  • NADH
  • Oxidative pentose phosphate pathway
  • Protein engineering
  • Redox balancing
  • Seaweed
  • Transhydrogenase

ASJC Scopus subject areas

  • Biotechnology
  • Bioengineering
  • Applied Microbiology and Biotechnology


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