The role of Saccharomyces cerevisiae in stabilizing emulsions of hexadecane in aqueous media
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During downstream operations involved in the purification of hydrophobic biofuels produced by microorganisms, undesired stable emulsions may be formed. Understanding the mechanisms behind this stability is a pre-requisite for designing cost-effective strategies to break these emulsions. In this work, we aimed at increasing our knowledge on the mechanisms responsible for stabilizing yeast-containing oil-in-water emulsions. For this purpose, emulsions containing hexadecane and different yeast-based aqueous phases were prepared and analyzed for phase separation, surface charge density, particle size, and rheology. First, we observed that compounds present in fresh tablet baker’s yeast contribute to emulsion stability. In order to eliminate this effect, we generated stocks with this yeast in the laboratory, and compared its performance with an industrial fuel ethanol strain, namely Saccharomyces cerevisiae PE-2. We confirmed that the presence of yeast cells enhances emulsion stability. The cultivation medium (complex or defined) in which cells are grown, as well as the physiological state of the cells (pre- or post-diauxic), prior to emulsion preparation, influenced emulsion stability. The smaller cell size of tablet yeast probably also contributes to more stable emulsions, when compared to those prepared with yeast cells grown in the laboratory. Baker’s and fuel ethanol yeast cells in post-diauxic phase promote the formation of more stable emulsions than those with cells in the pre-diauxic physiological state. Finally, we propose a mechanism to explain the enhanced emulsion stability due to the presence of yeast cells, with electrostatic repulsion between emulsion droplets having the prevailing effect.
KeywordsBiofuels Stability of emulsions Yeast Saccharomyces cerevisiae Hexadecane Downstream processing
This study was funded by Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP, São Paulo, Brazil), grant number 2011/51707-1. AADM received a M.Sc. scholarship from Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq, Brasília, Brazil).
Compliance with ethical standards
This article does not contain any studies with human participants or animals performed by any of the authors.
Conflict of interest
All authors declare that they have no conflicts of interest.
- EIA - International energy outlook (2016) Report DOE/EIA-0484 (2016). Energy information administration, US Department of Energy, Washington, DC https://www.eia.gov/outlooks/ieo/pdf/0484(2016).pdf. Accessed 16 June 2017Google Scholar
- Elsanusi OA, Roy MM, Sidhu MS (2017) Experimental investigation on a diesel engine fueled by diesel-biodiesel blends and their emulsions at various engine operating conditions. Appl Energy 203:582-593. https://doi.org/10.1016/j.apenergy.2017.06.052
- Furtado GF, Picone CSF, Cuellar MC, Cunha RL (2015) Breaking oil-in-water emulsions stabilized by yeast. Coll and Surf B: Biointerfaces 128(0):568–576. https://doi.org/10.1016/j.colsurfb.2015.03.010
- Goldemberg J, Schaeffer R, Szklo A, Lucchesi R (2014) Oil and natural gas prospects in South America: can the petroleum industry pave the way for renewables in Brazil?. Energy Policy 64(0):58–70. https://doi.org/10.1016/j.enpol.2013.05.064
- Gutiérrez CP (2008) Estudio, optimización y escalado de nanoemulsiones o/w preparadas por inversión de fases. Universitat de Barcelona, ThesisGoogle Scholar
- Heeres AS, Picone CSF, van der Wielen LAM, Cunha RL, Cuellar MC (2014) Microbial advanced biofuels production: overcoming emulsification challenges for large-scale operation. Trends Biotechnol 32(4):221–229. https://doi.org/10.1016/j.tibtech.2014.02.002
- Heeres AS, Heijnen JJ, van der Wielen LAM, Cuellar MC (2016) Gas bubble induced oil recovery from emulsions stabilised by yeast components. Chem Eng Sci 145:31–44. https://doi.org/10.1016/j.ces.2016.02.011
- Huang X, Peng K, Feng Y, Liu J, Lu L (2013) Separation and characterization of effective demulsifying substances from surface of Alcaligenes sp. S-XJ-1 and its application in water-in-kerosene emulsion. Bioresour. Technol 139:257–264. https://doi.org/10.1016/j.biortech.2013.04.043 CrossRefPubMedGoogle Scholar
- Jang Y-S, Park JM, Choi S, Choi YJ, Seung DY, Cho JH, Lee SY (2012) Engineering of microorganisms for the production of biofuels and perspectives based on systems metabolic engineering approaches. Biotechnol Adv 30(5):989–1000. https://doi.org/10.1016/j.biotechadv.2011.08.015
- Kerschner C, Prell C, Feng K, Hubacek K (2013) Economic vulnerability to peak oil. Glob Environ Chang 23(6):1424–1433. https://doi.org/10.1016/j.gloenvcha.2013.08.015
- Luttik MA, Kotter P, Salomons FA, van der Klei IJ, van Dijken JP, Pronk JT (2000) The Saccharomyces cerevisiae ICL2 gene encodes a mitochondrial 2-methylisocitrate lyase involved in propionyl-coenzyme A metabolism. J Bacteriol 182(24):7007–7013. https://doi.org/10.1128/JB.182.24.7007-7013.2000 CrossRefPubMedPubMedCentralGoogle Scholar
- Maggio G, Cacciola G (2012) When will oil, natural gas, and coal peak?. Fuel 98(0):111–123. https://doi.org/10.1016/j.fuel.2012.03.021
- McClements DJ (2005) Food emulsions: principles, practices, and techniques, 2° edn. CRC Press, Washington, D.C.Google Scholar
- Moreira TCP, da Silva VM, Gombert AK, da Cunha RL (2016) Stabilization mechanisms of oil-in-water emulsions by Saccharomyces cerevisiae Coll and Surf B: Biointerfaces 143:399–405. https://doi.org/10.1016/j.colsurfb.2016.03.043
- Renninger NS, Newman JD, Reiling KK (2007) Fuel components, fuel compositions and methods of making and using same. Patent WO 2007139925 A2Google Scholar
- Tibayrenc P, Preziosi-Belloy L, Roger J-M, Ghommidh C (2010) Assessing yeast viability from cell size measurements? J Biotechnol 149(1–2):74-80. https://doi.org/10.1016/j.jbiotec.2010.06.019
- Valle-Rodríguez JO, Shi S, Siewers V, Nielsen J (2014) Metabolic engineering of Saccharomyces cerevisiae for production of fatty acid ethyl esters, an advanced biofuel, by eliminating non-essential fatty acid utilization pathways. Appl Energy 115(0):226-232. https://doi.org/10.1016/j.apenergy.2013.10.003
- Walker GM (2000) Yeast physiology and biotchnology 2° edn. John Wiley & Sons, New York, ChichesterGoogle Scholar
- Werner-Washburne M, Braun EL, Crawford ME, Peck VM (1996) Stationary phase in Saccharomyces cerevisiae. Mol Microbiol 19(6):1159–1166. https://doi.org/10.1111/j.1365-2958.1996.tb02461.x CrossRefPubMedGoogle Scholar