Metabolic Engineering of Corynebacterium Glutamicum for the Utilization of Biomass-Derived Carbon and Energy Sources

Methanol is a pure and inexpensive raw material, which is mainly produced from fossil-fuel-based synthesis gas. Over the past years however, new approaches were developed for its production from renewable carbon sources. Methanol is an important carbon feedstock in the chemical industry, but has found only limited application in biotechnological production processes. This can be mostly attributed to the inability of most microbial platform organisms to utilize methanol as carbon and energy source. With the aim to turn methanol into a suitable feedstock for microbial production processes, we engineered the industrially important, but non-methylotrophic bacterium Corynebacterium glutamicum towards the utilization of methanol as auxiliary carbon source in a sugar-based medium [1,2].

Additionally, biomass-derived D-xylose represents an economically interesting substrate for the sustainable microbial production of value-added compounds. All currently described C. glutamicum strains utilize D-xylose via the commonly known isomerase pathway that leads to a significant carbon loss in the form of CO₂, in particular, when aiming for the synthesis of α-ketoglutarate and its derivatives (e.g. l-glutamate). Driven by the motivation to engineer a more carbon-efficient C. glutamicum strain, we functionally integrated the Weimberg pathway from Caulobacter crescentus in C. glutamicum [3]. This five-step pathway enabled a recombinant C. glutamicum strain to utilize D-xylose in D-xylose/D-glucose mixtures and thus represents a promising starting point for the engineering of efficient production strains, exhibiting only minimal carbon loss on D-xylose containing substrates.

 [1] Witthoff S., Mühlroth A., Marienhagen J., Bott M. (2013) C1 metabolism in Corynebacterium glutamicum: an endogenous pathway for oxidation of methanol to carbon dioxide. Appl. Environ. Microbiol. 79(22): 6974–6983.

 [2] Witthoff S., Schmitz K., Niedenführ S., Nöh K., Noack S., Bott M., Marienhagen J. (2015). Metabolic engineering of Corynebacterium glutamicum for the metabolization of methanol. Appl. Environ. Microbiol. 81(6): 2215–2225.

 [3] Radek A., Krumbach K., Gätgens J., Wendisch V. F., Wiechert W., Bott M., Noack S., Marienhagen J. (2014). Engineering of Corynebacterium glutamicum for minimized carbon loss during utilization of D-xylose containing substrates. J. Biotechnol. 192: 156–160.