Enhancing acetic acid and 5-hydroxymethyl furfural tolerance of C. saccharoperbutylacetonicum through adaptive laboratory evolution

Supplementary material related to this article can be found, in the online version, at doi:https://doi.org/10.1016/j.procbio.2020.11.013.In this study, adaptive laboratory evolution (ALE) was applied to isolate four strains of Clostridium saccharoperbutylacetonicum able to grow in the presence of hemicellulosic hydrolysate inhibitors unsupported by the parental strain. Among them, isolate RAC-25 presented the best fermentative performance, producing 22.1g/L of ABE and 16.7g/L of butanol. Genome sequencing revealed a deletion in the arabinose transcriptional repressor gene (araR) and a mutation in the anti-sigma factor I that promoted a downregulation of sigI. Gene expression analysis indicated high expression of genes related to H+-pumps (ATP synthases), proline biosynthesis (gamma phosphate reductase) and chaperonins (Grol), suggesting an integrated mechanism that is probably coordinated by the repression of sigI. Therefore, in addition to highlighting the power of ALE for selecting robust strains, our results suggest that sigI and araR may be interesting gene targets for increased tolerance toward inhibitor compounds relevant for lignocellulosic biofuels production.The authors would like to thank the Brazilian Center for Research in Energy and Materials (CNPEM) for providing access to the bioprocess facility of the Brazilian Biorenewables National Laboratory, and CNPq (400803/2013-5), FCT (UID/BIO/04469), BioTecNorte Operation (NORTE-01-0145-FEDER-000004) and Portuguese Biological Data Network” (ref. LISBOA-01-0145-FEDER-022231) for financial support.info:eu-repo/semantics/publishedVersio