Genome-scale metabolic modeling underscores the potential of Cutaneotrichosporon oleaginosus ATCC 20509 as a cell factory for biofuel production

Nhung Pham,Maarten Reijnders,Jan Springer,Bart Nijsse,Maria Suarez-Diez,Peter J Schaap,Gerrit Eggink

doi:10.1186/s13068-020-01838-1

Abstract

BackgroundCutaneotrichosporon oleaginosus ATCC 20509 is a fast-growing oleaginous basidiomycete yeast that is able to grow in a wide range of low-cost carbon sources including crude glycerol, a byproduct of biodiesel production. When glycerol is used as a carbon source, this yeast can accumulate more than 50% lipids (w/w) with high concentrations of mono-unsaturated fatty acids.ResultsTo increase our understanding of this yeast and to provide a knowledge base for further industrial use, a FAIR re-annotated genome was used to build a genome-scale, constraint-based metabolic model containing 1553 reactions involving 1373 metabolites in 11 compartments. A new description of the biomass synthesis reaction was introduced to account for massive lipid accumulation in conditions with high carbon-to-nitrogen (C/N) ratio in the media. This condition-specific biomass objective function is shown to better predict conditions with high lipid accumulation using glucose, fructose, sucrose, xylose, and glycerol as sole carbon source.ConclusionContributing to the economic viability of biodiesel as renewable fuel, C. oleaginosus ATCC 20509 can effectively convert crude glycerol waste streams in lipids as a potential bioenergy source. Performance simulations are essential to identify optimal production conditions and to develop and fine tune a cost-effective production process. Our model suggests ATP-citrate lyase as a possible target to further improve lipid production.

Highlights

Cutaneotrichosporon oleaginosus ATCC 20509 is a fast-growing oleaginous basidiomycete yeast that is able to grow in a wide range of low-cost carbon sources including crude glycerol, a byproduct of biodiesel pro‐ duction
C. oleaginosus appears to be one of the most accommodating and is able to grow in a wide range of industrially interesting operational conditions such as in food waste and municipal wastewater streams [7], whey permeate [8], office paper production waste streams [9, 10], spent yeast lysate from brewery industry and crude glycerol from biodiesel production [11, 12]
When the inexpensive waste product from biodiesel production, crude glycerol, is becoming abundantly available, this organism could play a major role in further upcycling of the biodiesel process, as lipids derived from C. oleaginosus grown on glycerol have high concentrations of monounsaturated fatty acids (MUFA) [18]

Summary

Results

For the formation of unsaturated fatty acids (C16:1, C18:1, and C18:2) a fatty acid desaturase is required [33]. Model prediction for lipid production in glycerol is noticeably different from that of other carbon sources This is consistent with findings in [44] who reported a maximum growth rate and lipid production of C. oleaginosus ATCC 20509 on glycerol in a fed-batch fermentation mode at 16 g/l glycerol and 0.27 g/l NH4Cl, corresponding to a C/N ratio of 100 mol/ mol. Using xylose as carbon source the Acetyl-CoA carboxylase (ACC) gene was found to be upregulated in Trichosporon oleaginosus strain IBC0246 under nitrogen limitation [52] and the same authors reported significant upregulation of fatty acid synthetase (FAS1 and FAS2), malic enzyme and ATP-citrate lyase (ACL) under these conditions. The model was able to predict lipid production at different C/N ratio qualitatively consistent with experimental data This suggests that in glycerol C. oleaginosus ATCC 20509 lipid metabolism is not regulated at the transcriptional level. Little is know on the regulation of this enzyme in C. oleaginosus

Conclusion

Background

Results and discussion

Conclusions

Materials and methods