Microaerobic growth-decoupled production of α-ketoglutarate and succinate from xylose in a one-pot process using Corynebacterium glutamicum

Background: Lignocellulosic biomass is the most abundant raw material on earth. Its efficient use for novel bio-based materials is essential for an emerging bioeconomy. Possible building blocks for such materials are the key TCA-cycle intermediates α-ketoglutarate and succinate. These organic acids have a wide range of potential applications, particularly in use as monomers for established or novel biopolymers. Recently, Corynebacterium glutamicum was successfully engineered and evolved towards an improved utilization of d-xylose via the Weimberg pathway, yielding the strain WMB2_evo . The Weimberg pathway enables a carbon-efficient C5-to-C5 conversion of d-xylose to α-ketoglutarate and a shortcut route to succinate as co-product in a one-pot process.

Methods and results: C. glutamicum WMB2_evo was grown under dynamic microaerobic conditions on d-xylose, leading to the formation of comparably high amounts of succinate and only small amounts of α-ketoglutarate. Subsequent carbon isotope labeling experiments verified the targeted production route for both products in C. glutamicum WMB2_evo . Fed-batch process development was initiated and the effect of oxygen supply and feeding strategy for a growth-decoupled co-production of α-ketoglutarate and succinate were studied in detail. The finally established fed-batch production process resulted in the formation of 78.4 mmol L^-1 (11.45 g L^-1 ) α-ketoglutarate and 96.2 mmol L^-1 (11.36 g L^-1 ) succinate.

Conclusion: The developed one-pot process represents a promising approach for the combined supply of bio-based α-ketoglutarate and succinate. Future work will focus on tailor-made down-stream processing of both organic acids from the fermentation broth to enable their application as building blocks in chemical syntheses. Alternatively, direct conversion of one or both acids via whole-cell or cell-free enzymatic approaches can be envisioned; thus, extending the network of value chains starting from cheap and renewable d-xylose.