Abstract
Furfural is a major inhibitor in lignocellulose hydrolysate for Zymomonas mobilis. A mutant F211 strain with high furfural tolerance was obtained from our previous study. Thus, its key tolerance mechanism was studied in the present study. The function of mutated genes in F211 was identified by functional complementation experiments, revealing that the improved furfural tolerance was resulted from the C493T mutation of the ZCP4_0270 gene promoting cell flocculation and the mutation (G1075A)/downregulation of ZCP4_0970. Comparative transcriptome analysis revealed 139 differentially expressed genes between F211 and the control, CP4, in response to furfural stress. In addition, the reliability of the RNA-Seq data was also confirmed. The potential tolerance mechanism was further demonstrated by functional identification of tolerance genes as follows: (I) some upregulated or downregulated genes increase the levels of NAD(P)H, which is involved in the reduction of furfural to less toxic furfuryl alcohol, thus accelerating the detoxification of furfural; (II) the mutated ZCP4_0270 and upregulated cellulose synthetase gene (ZCP4_0241 and ZCP4_0242) increased flocculation to resist furfural stress; (III) upregulated molecular chaperone genes promote protein synthesis and repair stress-damaged proteins; and (IV) transporter genes ZCP4_1623–1,625 and ZCP4_1702–1703 were downregulated, saving energy for cell growth. The furfural-tolerant mechanism and corresponding functional genes were revealed, which provides a theoretical basis for developing robust chassis strains for synthetic biology efforts.
Highlights
Lignocellulosic biomass is an abundant renewable and sustainable resource used to produce biofuels and high-value chemicals (Yang et al, 2020)
Zymomonas mobilis may respond to stress in the following ways: (1) conversion of furfural to furfuryl alcohol reduces toxicity (Wang et al, 2017); (2) the genes related to macromolecule synthesis are upregulated to resist furfural stress (Miller et al, 2009; Yang et al, 2020); and (3) transcription factors regulate the expression of multiple genes in response to stress (He et al, 2012; Nouri et al, 2020)
The high furfural tolerance mutant strain F211 was obtained in an earlier study, and single nucleotide polymorphisms (SNPs) between F211 and control strain CP4 were identified by genome resequencing of F211 (Huang et al, 2018); in this study, functional identification of the mutations and RNA-Seq was performed to investigate the genotypic changes associated with furfural tolerance and reveal the molecular mechanism responsible for the improved furfural tolerance in F211
Summary
Lignocellulosic biomass is an abundant renewable and sustainable resource used to produce biofuels and high-value chemicals (Yang et al, 2020). A facultative anaerobic gram-negative bacterium that naturally produces ethanol, has excellent characteristics, such as a high specific rate of sugar uptake and high theoretical ethanol yield (Wang et al, 2018) It is a promising chassis strain for the production of high value-added products from lignocellulosic biomass (He et al, 2014). Zymomonas mobilis may respond to stress in the following ways: (1) conversion of furfural to furfuryl alcohol reduces toxicity (Wang et al, 2017); (2) the genes related to macromolecule synthesis are upregulated to resist furfural stress (Miller et al, 2009; Yang et al, 2020); and (3) transcription factors regulate the expression of multiple genes in response to stress (He et al, 2012; Nouri et al, 2020). (Huang et al, 2018); in this study, functional identification of the mutations and RNA-Seq was performed to investigate the genotypic changes associated with furfural tolerance and reveal the molecular mechanism responsible for the improved furfural tolerance in F211
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
