Abstract
Lignocellulosic ethanol is produced by yeast fermentation of lignocellulosic hydrolysates generated by chemical pretreatment and enzymatic hydrolysis of plant cell walls. The conversion of xylose into ethanol in hydrolysates containing microbial inhibitors is a major bottleneck in biofuel production. We identified sodium salts as the primary yeast inhibitors, and evolved a Saccharomyces cerevisiae strain overexpressing xylose catabolism genes in xylose or glucose-mixed medium containing sodium salts. The fully evolved yeast strain can efficiently convert xylose in the hydrolysates to ethanol on an industrial scale. We elucidated that the amplification of xylA, XKS1 and pentose phosphate pathway-related genes TAL1, RPE1, TKL1, RKI1, along with mutations in NFS1, TRK1, SSK1, PUF2 and IRA1, are responsible and sufficient for the effective xylose utilization in corn stover hydrolysates containing high sodium salts. Our evolved or reverse-engineered yeast strains enable industrial-scale production of lignocellulosic ethanol and the genetic foundation we uncovered can also facilitate transfer of the phenotype to yeast cell factories producing chemicals beyond ethanol.
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Data availability
The raw data of whole-genome sequencing and RNA sequencing in this work have been deposited in the NCBI under the project accession number PRJNA827654. Haploid genome assembly and annotation have been deposited under the NCBI project accession number PRJNA556784. The proteomics sequencing datasets have been submitted to the iProX database with the project ID IPX0004391000. Source data are provided with this paper.
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Acknowledgements
We thank H.-Y. Ren, W. Li and H. Yang from Novozymes for corn stover hydrolysates preparation, phenotype confirmation and research suggestions; J. Chen, Y.-M. Liu, L.-Y. Diao, X. Wang, J.-L. Liu, Y.-Y. Kong, J. Zhu, L.-Y. Wang and S. Xu from S.Y.’s laboratory for assistance with the experiments; X. Li and X.-T. Li from the Chinese Academy of Science for GWAS analyses; and Z.-J. Li from Angel Yeast, Z.-B. Shen from Tianguan and F.-Y. Bai and F.-L. Li from the Chinese Academy of Science for helpful suggestions on yeast chassis selection. This work was supported by National Natural Science Foundation of China (grant nos. 21825804 and 31921006), National Key R&D Program of China (grant nos. 2021YFC2103703, 2023YFF1000202) to S.Y.
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W.-P.W. and S.Y. conceived the project. S.Y., W.-P.W., C.H., J.-J.Y. and Y.-W.Z. designed the experiments. F.-H.Q. and Y.-W.Z. performed most of the experiments. S.Y., Y.J., J.-J.Y. and Y.-W.Z. analyzed the data. C.H. and K.B.S. helped with experiments. J.-J.Y. performed the bioinformatic analyses in this study. S.Y., Y.-W.Z., J.-J.Y. and Y.J. discussed the data and wrote the paper.
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This work was partially funded by Novozymes. Patent applications have been filed by the Novozymes, Shanghai Research and Development Center of Industrial Biotechnology (CIBT) and Center for Excellence of Molecular Plant Science (CEMPS) based on this work. The pending patent application (application number WO2016045569) covers the method for producing lignocellulosic ethanol using evolved yeasts in this study. The patent applicant is Novozymes and K.B.S., Y.J., S.Y. and F.-H.Q. are listed as inventors. S.Y., J.-J.Y. and Y.J. are inventors of a granted patent related to the NFS1 variant for improving xylose use in S. cerevisiae (patent number CN202010475833.9). The patent applicant is CEMPS. The pending patent application (application number CN2023074360) covers the other gene targets for improving S. cerevisiae’s performance in lignocellulosic hydrolysates in this study. The patent applicant is CEMPS and CIBT and S.Y., Y.-W.Z., J.-J.Y., F.-H.Q. and Y.J. are listed as inventors. S.Y. has contributed to the scientific advisory board at Angel Yeast. Some authors receive royalty payment from xylose yeast customers. The other authors declare no competing interests.
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Zhang, YW., Yang, JJ., Qian, FH. et al. Engineering a xylose fermenting yeast for lignocellulosic ethanol production. Nat Chem Biol (2024). https://doi.org/10.1038/s41589-024-01771-6
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DOI: https://doi.org/10.1038/s41589-024-01771-6