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Updated: Oct 19, 2026

Metabolic Pathway Confirmation and Discovery Through 13C-labeling of Proteinogenic Amino Acids
Published on: January 26, 2012
Carbon-loss-guided metabolic engineering improved carbon atom economy and industrial feedstock utilization for
Jianhang Liu1, Qi Sheng1, Chao Ye2
1School of Biotechnology and Key Laboratory of Industrial Biotechnology of Ministry of Education, Jiangnan University, Wuxi 214122, China.
Abstract:
l-Threonine is a high-value amino acid widely used in the feed, food, and pharmaceutical industries, but its industrial production is limited by low yield. In this study, whole-genome sequencing of industrial strain Thr1 was performed, and the genome-scale metabolic model GSMM-iJHL1061 was reconstructed. The model identified 54 CO2-related reactions and predicted 0.89 mol CO2 release per mol l-threonine synthesized, mainly from the PPP and TCA cycle. Attenuation of decarboxylation reactions involving ilvBN, lysA, gnd, and icd, combined with RuBisCO-Prk and cynT-pyc-based CO2 fixation, increased the yield to 0.66 g/g. Deletion of 166 non-essential genes generated Thr9, increasing the yield to 0.67 g/g. Further introduction of maltose hydrolysis and sucrose utilization systems generated Thr10, which produced 132.5 g/L l-threonine in a 1000-L fermenter, with a yield of 0.68 g/g. Overall, l-threonine yield was substantially improved through systems metabolic engineering, providing a useful reference for constructing high-yield microbial cell factories.
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