BACKGROUND: Biobutanol production by clostridia via the acetone-butanol-ethanol (ABE) pathway is a promising future technology in bioenergetics , but identifying key regulatory mechanisms for this pathway is essential in order to construct industrially relevant strains with high tolerance and productivity. We have applied flow cytometric analysis to C. beijerinckii NRRL B-598 and carried out comparative screening of physiological changes in terms of viability under different cultivation conditions to determine its dependence on particular stages of the life cycle and the concentration of butanol. RESULTS: Dual staining by propidium iodide (PI) and carboxyfluorescein diacetate (CFDA) provided separation of cells into four subpopulations with different abilities to take up PI and cleave CFDA, reflecting different physiological states. The development of a staining pattern during ABE fermentation showed an apparent decline in viability, starting at the pH shift and onset of solventogenesis, although an appreciable proportion of cells continued to proliferate. This was observed for sporulating as well as non-sporulating phenotypes at low solvent concentrations, suggesting that the increase in percentage of inactive cells was not a result of solvent toxicity or a transition from vegetative to sporulating stages. Additionally, the sporulating phenotype was challenged with butanol and cultivation with a lower starting pH was performed; in both these experiments similar trends were obtained-viability declined after the pH breakpoint, independent of the actual butanol concentration in the medium. Production characteristics of both sporulating and non-sporulating phenotypes were comparable, showing that in C. beijerinckii NRRL B-598, solventogenesis was not conditional on sporulation. CONCLUSION: We have shown that the decline in C. beijerinckii NRRL B-598 culture viability during ABE fermentation was not only the result of accumulated toxic metabolites, but might also be associated with a special survival strategy triggered by pH change.

Department of Biotechnology University of Chemistry and Technology Prague Technicka 5 166 28 Prague Czech Republic

Zobrazit více v PubMed

Jones DT, Woods DR. Acetone–butanol fermentation revisited. Microbiol Rev. 1986;50:484–524. PubMed PMC

Yusri IM, Mamat R, Najafi G, Razman A, Awad OI, Azmi WH, Ishak WFW, Shaiful AIM. Alcohol based automotive fuels from first four alcohol family in compression and spark ignition engine: a review on engine performance and exhaust emissions. Renew Sustain Energy Rev. 2017;77:169–181. doi: 10.1016/j.rser.2017.03.080. DOI

Pfromm PH, Amanor-Boadu V, Nelson R, Vadlani P, Madl R. Bio-butanol vs. bio-ethanol: a technical and economic assessment for corn and switchgrass fermented by yeast or Clostridium acetobutylicum. Biomass Bioenergy. 2010;34:515–524. doi: 10.1016/j.biombioe.2009.12.017. DOI

Poehlein A, Solano JDM, Flitsch SK, Krabben P, Winzer K, Reid SJ, Jones DT, Green E, Minton NP, Daniel R, Durre P. Microbial solvent formation revisited by comparative genome analysis. Biotechnol Biofuels. 2017;10:15. doi: 10.1186/s13068-017-0742-z. PubMed DOI PMC

Jiang Y, Liu J, Jiang W, Yang Y, Yang S. Current status and prospects of industrial bio-production of n-butanol in China. Biotechnol Adv. 2015;33:1493–1501. doi: 10.1016/j.biotechadv.2014.10.007. PubMed DOI

Becerra M, Cerdán ME, González-Siso MI. Biobutanol from cheese whey. Microb Cell Fact. 2015;14:27. doi: 10.1186/s12934-015-0200-1. PubMed DOI PMC

Wang XF, Zhang ZT, Wang Y, Wang YF. Improvement of acetone–butanol–ethanol (ABE) production from switchgrass pretreated with a radio frequency-assisted heating process. Fuel. 2016;182:166–173. doi: 10.1016/j.fuel.2016.05.108. DOI

Ezeji TC, Qureshi N, Blaschek HP. Bioproduction of butanol from biomass: from genes to bioreactors. Curr Opin Biotechnol. 2007;18:220–227. doi: 10.1016/j.copbio.2007.04.002. PubMed DOI

Qureshi N, Liu S, Hughes S, Palmquist D, Dien B, Saha B. Cellulosic butanol (ABE) biofuel production from sweet sorghum bagasse (SSB): impact of hot water pretreatment and solid loadings on fermentation employing Clostridium beijerinckii P260. Bioenergy Res. 2016;9:1167–1179. doi: 10.1007/s12155-016-9761-z. DOI

Huang HB, Singh V, Qureshi N. Butanol production from food waste: a novel process for producing sustainable energy and reducing environmental pollution. Biotechnol Biofuels. 2015;8:12. doi: 10.1186/s13068-014-0194-7. PubMed DOI PMC

Gallazzi A, Branska B, Marinelli F, Patakova P. Continuous production of n-butanol by Clostridium pasteurianum DSM 525 using suspended and surface-immobilized cells. J Biotechnol. 2015;216:29–35. doi: 10.1016/j.jbiotec.2015.10.008. PubMed DOI

Qureshi N, Lai LL, Blaschek HP. Scale-up of a high productivity continuous biofilm reactor to produce butanol by adsorbed cells of Clostridium beijerinckii. Food Bioprod Process. 2004;82:164–173. doi: 10.1205/0960308041614891. DOI

Li HG, Ma XX, Zhang QH, Luo W, Wu YQ, Li XH. Enhanced butanol production by solvent tolerance Clostridium acetobutylicum SE25 from cassava flour in a fibrous bed bioreactor. Bioresour Technol. 2016;221:412–418. doi: 10.1016/j.biortech.2016.08.120. PubMed DOI

Wen Z, Wu M, Lin Y, Yang L, Lin J, Cen P. Artificial symbiosis for acetone–butanol–ethanol (ABE) fermentation from alkali extracted deshelled corn cobs by co-culture of Clostridium beijerinckii and Clostridium cellulovorans. Microb Cell Fact. 2014;13:92. doi: 10.1186/s12934-014-0092-5. PubMed DOI PMC

Wu PF, Wang GY, Wang GH, Borresen BT, Liu HJ, Zhang JN. Butanol production under microaerobic conditions with a symbiotic system of Clostridium acetobutylicum and Bacillus cereus. Microb Cell Fact. 2016;15:11. doi: 10.1186/s12934-015-0397-z. PubMed DOI PMC

Yen HW, Wang YC. The enhancement of butanol production by in situ butanol removal using biodiesel extraction in the fermentation of ABE (acetone–butanol–ethanol) Bioresour Technol. 2013;145:224–228. doi: 10.1016/j.biortech.2012.11.039. PubMed DOI

Wang YR, Chiang YS, Chuang PJ, Chao YP, Li SY. Direct in situ butanol recovery inside the packed bed during continuous acetone–butanol–ethanol (ABE) fermentation. Appl Microbiol Biotechnol. 2016;100:7449–7456. doi: 10.1007/s00253-016-7443-6. PubMed DOI

Mariano AP, Qureshi N, Maciel R, Ezeji TC. Bioproduction of butanol in bioreactors: new insights from simultaneous in situ butanol recovery to eliminate product toxicity. Biotechnol Bioeng. 2011;108:1757–1765. doi: 10.1002/bit.23123. PubMed DOI

Liu XB, Gu QY, Liao CL, Yu XB. Enhancing butanol tolerance and preventing degeneration in Clostridium acetobutylicum by 1-butanol-glycerol storage during long-term preservation. Biomass Bioenergy. 2014;69:192–197. doi: 10.1016/j.biombioe.2014.07.019. DOI

Liu XB, Gu QY, Yu XB. Repetitive domestication to enhance butanol tolerance and production in Clostridium acetobutylicum through artificial simulation of bio-evolution. Bioresour Technol. 2013;130:638–643. doi: 10.1016/j.biortech.2012.12.121. PubMed DOI

Zingaro KA, Papoutsakis ET. Toward a semisynthetic stress response system to engineer microbial solvent tolerance. Mbio. 2012;3:9. doi: 10.1128/mBio.00308-12. PubMed DOI PMC

Xue C, Zhao J, Chen L, Yang S-T, Bai F. Recent advances and state-of-the-art strategies in strain and process engineering for biobutanol production by Clostridium acetobutylicum. Biotechnol Adv. 2017;35:310–322. doi: 10.1016/j.biotechadv.2017.01.007. PubMed DOI

Dusséaux S, Croux C, Soucaille P, Meynial-Salles I. Metabolic engineering of Clostridium acetobutylicum ATCC 824 for the high-yield production of a biofuel composed of an isopropanol/butanol/ethanol mixture. Metab Eng. 2013;18:1–8. doi: 10.1016/j.ymben.2013.03.003. PubMed DOI

Pyne ME, Bruder M, Moo-Young M, Chung DA, Chou CP. Technical guide for genetic advancement of underdeveloped and intractable Clostridium. Biotechnol Adv. 2014;32:623–641. doi: 10.1016/j.biotechadv.2014.04.003. PubMed DOI

Lütke-Eversloh T, Bahl H. Metabolic engineering of Clostridium acetobutylicum: recent advances to improve butanol production. Curr Opin Biotechnol. 2011;22:634–647. doi: 10.1016/j.copbio.2011.01.011. PubMed DOI

Kuit W, Minton NP, López-Contreras AM, Eggink G. Disruption of the acetate kinase (ack) gene of Clostridium acetobutylicum results in delayed acetate production. Appl Microbiol Biotechnol. 2012;94:729–741. doi: 10.1007/s00253-011-3848-4. PubMed DOI PMC

Wang S, Dong S, Wang Y. Enhancement of solvent production by overexpressing key genes of the acetone–butanol–ethanol fermentation pathway in Clostridium saccharoperbutylacetonicum N1-4. Bioresour Technol. 2017;245:426–433. doi: 10.1016/j.biortech.2017.09.024. PubMed DOI

Jang YS, Lee JY, Lee J, Park JH, Im JA, Eom MH, Lee J, Lee SH, Song H, Cho JH, et al. Enhanced butanol production obtained by reinforcing the direct butanol-forming route in Clostridium acetobutylicum. mBio. 2012;3:e00314-12. doi: 10.1128/mBio.00314-12. PubMed DOI PMC

Zhao YS, Hindorff LA, Chuang A, Monroe-Augustus M, Lyristis M, Harrison ML, Rudolph FB, Bennett GN. Expression of a cloned cyclopropane fatty acid synthase gene reduces solvent formation in Clostridium acetobutylicum ATCC 824. Appl Environ Microbiol. 2003;69:2831–2841. doi: 10.1128/AEM.69.5.2831-2841.2003. PubMed DOI PMC

Mann MS, Dragovic Z, Schirrmacher G, Lütke-Eversloh T. Over-expression of stress protein-encoding genes helps Clostridium acetobutylicum to rapidly adapt to butanol stress. Biotechnol Lett. 2012;34:1643–1649. doi: 10.1007/s10529-012-0951-2. PubMed DOI

Rühl J, Schmid A, Blank LM. Selected Pseudomonas putida strains able to grow in the presence of high butanol concentrations. Appl Environ Microbiol. 2009;75:4653–4656. doi: 10.1128/AEM.00225-09. PubMed DOI PMC

Bowles LK, Ellefson WL. Effects of butanol on Clostridium acetobutylicum. Appl Environ Microbiol. 1985;50:1165–1170. PubMed PMC

Peabody GL, Kao KC. Recent progress in biobutanol tolerance in microbial systems with an emphasis on Clostridium. FEMS Microbiol Lett. 2016;363:fnw017. doi: 10.1093/femsle/fnw017. PubMed DOI

Liu Z, Qiao K, Tian L, Zhang Q, Liu ZY, Li FL. Spontaneous large-scale autolysis in Clostridium acetobutylicum contributes to generation of more spores. Front Microbiol. 2015;6:950. PubMed PMC

Kolek J, Branska B, Drahokoupil M, Patakova P, Melzoch K. Evaluation of viability, metabolic activity and spore quantity in clostridial cultures during ABE fermentation. FEMS Microbiol Lett. 2016;363:fnw031. doi: 10.1093/femsle/fnw031. PubMed DOI

Linhová M, Branská B, Patáková P, Lipovský J, Fribert P, Rychtera M, Melzoch K. Rapid flow cytometric method for viability determination of solventogenic clostridia. Folia Microbiol. 2012;57:307–311. doi: 10.1007/s12223-012-0131-8. PubMed DOI

Tracy BP, Gaida SM, Papoutsakis ET. Development and application of flow-cytometric techniques for analyzing and sorting endospore-forming Clostridia. Appl Environ Microbiol. 2008;74:7497–7506. doi: 10.1128/AEM.01626-08. PubMed DOI PMC

Jones SW, Paredes CJ, Tracy B, Cheng N, Sillers R, Senger RS, Papoutsakis ET. The transcriptional program underlying the physiology of clostridial sporulation. Genome Biol. 2008;9:R114. doi: 10.1186/gb-2008-9-7-r114. PubMed DOI PMC

Linhová M, Patáková P, Lipovský J, Fribert P, Paulová L, Rychtera M, Melzoch K. Development of flow cytometry technique for detection of thinning of peptidoglycan layer as a result of solvent production by Clostridium pasteurianum. Folia Microbiol. 2010;55:340–344. doi: 10.1007/s12223-010-0054-1. PubMed DOI

Díaz M, Herrero M, García LA, Quirós C. Application of flow cytometry to industrial microbial bioprocesses. Biochem Eng J. 2010;48:385–407. doi: 10.1016/j.bej.2009.07.013. DOI

Shapiro HM. Parameters and probes. In: Practical flow cytometry. New York: Wiley; 2005. p. 273–410. 10.1002/0471722731.ch7.

Want A, Hancocks H, Thomas CR, Stocks SM, Nebe-von-Caron G, Hewitt CJ. Multi-parameter flow cytometry and cell sorting reveal extensive physiological heterogeneity in Bacillus cereus batch cultures. Biotechnol Lett. 2011;33:1395–1405. doi: 10.1007/s10529-011-0566-z. PubMed DOI

Shi L, Gunther S, Hubschmann T, Wick LY, Harms H, Muller S. Limits of propidium iodide as a cell viability indicator for environmental bacteria. Cytometry Part A. 2007;71A:592–598. doi: 10.1002/cyto.a.20402. PubMed DOI

Kolek J, Diallo M, Vasylkivska M, Branska B, Sedlar K, López-Contreras AM, Patakova P. Comparison of expression of key sporulation, solventogenic and acetogenic genes in C. beijerinckii NRRL B-598 and its mutant strain overexpressing spo0A. Appl Microbiol Biotechnol. 2017;101:8279–8291. doi: 10.1007/s00253-017-8555-3. PubMed DOI

Liao ZP, Zhang YN, Luo S, Suo YK, Zhang SZ, Wang JF. Improving cellular robustness and butanol titers of Clostridium acetobutylicum ATCC824 by introducing heat shock proteins from an extremophilic bacterium. J Biotechnol. 2017;252:1–10. doi: 10.1016/j.jbiotec.2017.04.031. PubMed DOI

Jones AJ, Venkataramanan KP, Papoutsakis T. Overexpression of two stress-responsive, small, non-coding RNAs, 6S and tmRNA, imparts butanol tolerance in Clostridium acetobutylicum. FEMS Microbiol Lett. 2016;363:6. doi: 10.1093/femsle/fnw063. PubMed DOI

Tomas CA, Welker NE, Papoutsakis ET. Overexpression of groESL in Clostridium acetobutylicum results in increased solvent production and tolerance, prolonged metabolism, and changes in the cell’s transcriptional program. Appl Environ Microbiol. 2003;69:4951–4965. doi: 10.1128/AEM.69.8.4951-4965.2003. PubMed DOI PMC

Takano S, Pawlowska BJ, Gudelj I, Yomo T, Tsuru S. Density-dependent recycling promotes the long-term survival of bacterial populations during periods of starvation. mBio. 2017;8:e02336-02316. doi: 10.1128/mBio.02336-16. PubMed DOI PMC

Allcock ER, Reid SJ, Jones DT, Woods DR. Autolytic activity and an autolysis deficient mutant of Clostridium acetobutylicum. Appl Environ Microbiol. 1981;42:929–935. PubMed PMC

Vanderwesthuizen A, Jones DT, Woods DR. Autolytic activity and butanol tolerance of Clostridium acetobutylicum. Appl Environ Microbiol. 1982;44:1277–1281. PubMed PMC

Sandoval NR, Venkataramanan KP, Groth TS, Papoutsakis ET. Whole-genome sequence of an evolved Clostridium pasteurianum strain reveals Spo0A deficiency responsible for increased butanol production and superior growth. Biotechnol Biofuels. 2015;8:227. doi: 10.1186/s13068-015-0408-7. PubMed DOI PMC

Liu H, Huang D, Wen J. Integrated intracellular metabolic profiling and pathway analysis approaches reveal complex metabolic regulation by Clostridium acetobutylicum. Microb Cell Fact. 2016;15:36. doi: 10.1186/s12934-016-0436-4. PubMed DOI PMC

Zhang Y, Jiao SY, Lv J, Du RJ, Yan XN, Wan CX, Zhang RJ, Han B. Sigma factor regulated cellular response in a non-solvent producing Clostridium beijerinckii degenerated strain: a comparative transcriptome analysis. Front Microbiol. 2017;8:12. PubMed PMC

Sedlar K, Kolek J, Provaznik I, Patakova P. Reclassification of non-type strain Clostridium pasteurianum NRRL B-598 as Clostridium beijerinckii NRRL B-598. J Biotechnol. 2017;244:1–3. doi: 10.1016/j.jbiotec.2017.01.003. PubMed DOI

Müller S, Nebe-von-Caron G. Functional single-cell analyses: flow cytometry and cell sorting of microbial populations and communities. FEMS Microbiol Rev. 2010;34:554–587. doi: 10.1111/j.1574-6976.2010.00214.x. PubMed DOI

Tracy BP, Gaida SM, Papoutsakis ET. Flow cytometry for bacteria: enabling metabolic engineering, synthetic biology and the elucidation of complex phenotypes. Curr Opin Biotechnol. 2010;21:85–99. doi: 10.1016/j.copbio.2010.02.006. PubMed DOI

Müller S, Davey H. Recent advances in the analysis of individual microbial cells. Cytometry Part A. 2009;75A:83–85. doi: 10.1002/cyto.a.20702. PubMed DOI

González-Peñas H, Lu-Chau TA, Moreira MT, Lema JM. Assessment of morphological changes of Clostridium acetobutylicum by flow cytometry during acetone/butanol/ethanol extractive fermentation. Biotechnol Lett. 2015;37:577–584. doi: 10.1007/s10529-014-1702-3. PubMed DOI

Patakova P, Linhova M, Vykydalova P, Branska B, Rychtera M, Melzoch K. Use of fluorescent staining and flow cytometry for monitoring physiological changes in solventogenic clostridia. Anaerobe. 2014;29:113–117. doi: 10.1016/j.anaerobe.2013.10.006. PubMed DOI

Paulová L, Hyka P, Branská B, Melzoch K, Kovar K. Use of a mixture of glucose and methanol as substrates for the production of recombinant trypsinogen in continuous cultures with Pichia pastoris Mut+ J Biotechnol. 2012;157:180–188. doi: 10.1016/j.jbiotec.2011.10.010. PubMed DOI

Sekavova B, Melzoch K, Paulova L, Rychtera M. Application of flow cytometry to Saccharomyces cerevisiae population analysis. Chimia. 2005;59:745–748. doi: 10.2533/000942905777675741. DOI

Hewitt CJ, Nebe-Von-Caron G. An industrial application of multiparameter flow cytometry: assessment of cell physiological state and its application to the study of microbial fermentations. Cytometry. 2001;44:179–187. doi: 10.1002/1097-0320(20010701)44:3<179::AID-CYTO1110>3.0.CO;2-D. PubMed DOI

Millat T, Janssen H, Thorn GJ, King JR, Bahl H, Fischer RJ, Wolkenhauer O. A shift in the dominant phenotype governs the pH-induced metabolic switch of Clostridium acetobutylicum in phosphate-limited continuous cultures. Appl Microbiol Biotechnol. 2013;97:6451–6466. doi: 10.1007/s00253-013-4860-7. PubMed DOI

Nicolaou SA, Gaida SM, Papoutsakis ET. A comparative view of metabolite and substrate stress and tolerance in microbial bioprocessing: from biofuels and chemicals, to biocatalysis and bioremediation. Metab Eng. 2010;12:307–331. doi: 10.1016/j.ymben.2010.03.004. PubMed DOI

Mukhopadhyay A. Tolerance engineering in bacteria for the production of advanced biofuels and chemicals. Trends Microbiol. 2015;23:498–508. doi: 10.1016/j.tim.2015.04.008. PubMed DOI

Wang FQ, Kashket S, Kashket ER. Maintenance of Delta pH by a butanol-tolerant mutant of Clostridium beijerinckii. Microbiology. 2005;151:607–613. doi: 10.1099/mic.0.27587-0. PubMed DOI

Branduardi P, Porro D. n-butanol: challenges and solutions for shifting natural metabolic pathways into a viable microbial production. FEMS Microbiol Lett. 2016;363:7. doi: 10.1093/femsle/fnw070. PubMed DOI

Grimmler C, Janssen H, Krausse D, Fischer RJ, Bahl H, Durre P, Liebl W, Ehrenreich A. Genome-wide gene expression analysis of the switch between acidogenesis and solventogenesis in continuous cultures of Clostridium acetobutylicum. J Mol Microbiol Biotechnol. 2011;20:1–15. doi: 10.1159/000320973. PubMed DOI

Harris LM, Welker NE, Papoutsakis ET. Northern, morphological, and fermentation analysis of spo0A inactivation and overexpression in Clostridium acetobutylicum ATCC 824. J Bacteriol. 2002;184:3586–3597. doi: 10.1128/JB.184.13.3586-3597.2002. PubMed DOI PMC

Xue Q, Yang Y, Chen J, Chen L, Yang S, Jiang W, Gu Y. Roles of three AbrBs in regulating two-phase Clostridium acetobutylicum fermentation. Appl Microbiol Biotechnol. 2016;100:9081–9089. doi: 10.1007/s00253-016-7638-x. PubMed DOI

Steiner E, Scott J, Minton NP, Winzer K. An agr quorum sensing system that regulates granulose formation and sporulation in Clostridium acetobutylicum. Appl Environ Microbiol. 2012;78:1113–1122. doi: 10.1128/AEM.06376-11. PubMed DOI PMC

Jabbari S, Steiner E, Heap JT, Winzer K, Minton NP, King JR. The putative influence of the agr operon upon survival mechanisms used by Clostridium acetobutylicum. Math Biosci. 2013;243:223–239. doi: 10.1016/j.mbs.2013.03.005. PubMed DOI

Zingaro KA, Nicolaou SA, Papoutsakis ET. Dissecting the assays to assess microbial tolerance to toxic chemicals in bioprocessing. Trends Biotechnol. 2013;31:643–653. doi: 10.1016/j.tibtech.2013.08.005. PubMed DOI

Wang YF, Tian J, Ji ZH, Song M-Y, Li H. Intracellular metabolic changes of Clostridium acetobutylicum and promotion to butanol tolerance during biobutanol fermentation. Int J Biochem Cell Biol. 2016;78:297–306. doi: 10.1016/j.biocel.2016.07.031. PubMed DOI

Kanchanatawee S, Maddox IS. Effect of biomass concentration on the specific solvent productivity of Clostridium acetobutylicum in chemostat culture. J Ind Microbiol. 1991;7:151–154. doi: 10.1007/BF01576078. DOI

Qureshi N, Paterson AHJ, Maddox IS. Model for continuous production of solvents from whey permeate in a packed bed reactor using cells of Clostridium acetobutylicum immobilized by adsorption onto bonechar. Appl Microbiol Biotechnol. 1988;29:323–328. doi: 10.1007/BF00265814. DOI

Jain MK, Beacom D, Datta R. Mutant strain of C. acetobutylicum and process for making butanol. Google Patents, United States Patent US5192673A; 1993.

Sedlar K, Kolek J, Skutkova H, Branska B, Provaznik I, Patakova P. Complete genome sequence of Clostridium pasteurianum NRRL B-598, a non-type strain producing butanol. J Biotechnol. 2015;214:113–114. doi: 10.1016/j.jbiotec.2015.09.022. PubMed DOI

Lignocellulose-derived inhibitors can extend residence of Clostridium beijerinckii in active solventogenic state

Application of fed-batch strategy to fully eliminate the negative effect of lignocellulose-derived inhibitors in ABE fermentation

Effect of a Monascus sp. Red Yeast Rice Extract on Germination of Bacterial Spores

Deeper below the surface-transcriptional changes in selected genes of Clostridium beijerinckii in response to butanol shock

Changes in efflux pump activity of Clostridium beijerinckii throughout ABE fermentation

Phenotypic and Genomic Analysis of Clostridium beijerinckii NRRL B-598 Mutants With Increased Butanol Tolerance

A transcriptional response of Clostridium beijerinckii NRRL B-598 to a butanol shock

Acidogenesis, solventogenesis, metabolic stress response and life cycle changes in Clostridium beijerinckii NRRL B-598 at the transcriptomic level