Bioproduction of succinic acid from xylose by engineered Yarrowia lipolytica without pH control

Ashish A Prabhu; Rodrigo Ledesma-Amaro; Carol Sze Ki Lin; Frederic Coulon; Vijay Kumar Thakur; Vinod Kumar

doi:10.1186/s13068-020-01747-3

Bioproduction of succinic acid from xylose by engineered Yarrowia lipolytica without pH control

Biotechnol Biofuels. 2020 Jun 27:13:113. doi: 10.1186/s13068-020-01747-3. eCollection 2020.

Authors

Ashish A Prabhu¹, Rodrigo Ledesma-Amaro², Carol Sze Ki Lin³, Frederic Coulon¹, Vijay Kumar Thakur⁴, Vinod Kumar¹

Affiliations

¹ School of Water, Energy and Environment, Cranfield University, Cranfield, MK43 0AL UK.
² Department of Bioengineering and Imperial College Centre for Synthetic Biology, Imperial College London, London, SW7 2AZ UK.
³ School of Energy and Environment, City University of Hong Kong, Kowloon Tong, Kowloon, Hong Kong.
⁴ Biorefining and Advanced Materials Research Centre, Scotland's Rural College (SRUC), Edinburgh, UK.

Abstract

Background: Xylose is the most prevalent sugar available in hemicellulose fraction of lignocellulosic biomass (LCB) and of great interest for the green economy. Unfortunately, most of the cell factories cannot inherently metabolize xylose as sole carbon source. Yarrowia lipolytica is a non-conventional yeast that produces industrially important metabolites. The yeast is able to metabolize a large variety of substrates including both hydrophilic and hydrophobic carbon sources. However, Y. lipolytica lacks effective metabolic pathway for xylose uptake and only scarce information is available on utilization of xylose. For the economica feasibility of LCB-based biorefineries, effective utilization of both pentose and hexose sugars is obligatory.

Results: In the present study, succinic acid (SA) production from xylose by Y. lipolytica was examined. To this end, Y. lipolytica PSA02004 strain was engineered by overexpressing pentose pathway cassette comprising xylose reductase (XR), xylitol dehydrogenase (XDH) and xylulose kinase (XK) gene. The recombinant strain exhibited a robust growth on xylose as sole carbon source and produced substantial amount of SA. The inhibition of cell growth and SA formation was observed above 60 g/L xylose concentration. The batch cultivation of the recombinant strain in a bioreactor resulted in a maximum biomass concentration of 7.3 g/L and SA titer of 11.2 g/L with the yield of 0.19 g/g. Similar results in terms of cell growth and SA production were obtained with xylose-rich hydrolysate derived from sugarcane bagasse. The fed-batch fermentation yielded biomass concentration of 11.8 g/L (OD₆₀₀: 56.1) and SA titer of 22.3 g/L with a gradual decrease in pH below 4.0. Acetic acid was obtained as a main by-product in all the fermentations.

Conclusion: The recombinant strain displayed potential for bioconversion of xylose to SA. Further, this study provided a new insight on conversion of lignocellulosic biomass into value-added products. To the best of our knowledge, this is the first study on SA production by Y. lipolytica using xylose as a sole carbon source.

Keywords: Acetic acid; Succinic acid; Xylose; Yarrowia lipolytica; pH.