Cell recycling during repeated very high gravity bio-ethanol fermentations using the industrial Saccharomyces cerevisiae strain PE-2
A very high gravity (VHG) repeated-batch fermentation system using an industrial strain of Saccharomyces cerevisiae PE-2 (isolated from sugarcane-to-ethanol distillery in Brazil) and mimicking industrially relevant conditions (high inoculation rates and low O2 availability) was successfully operated during fifteen consecutive fermentation cycles, attaining ethanol at 17.1 ± 0.2% (v/v) with a batch productivity of 3.5 ± 0.04 g l−1 h−1. Moreover, this innovative operational strategy (biomass refreshing step) prevented critical decreases on yeast viability levels and promoted high accumulation of intracellular glycerol and trehalose, which can provide an adaptive advantage to yeast cells under harsh industrial environments. This study contributes to the improvement of VHG fermentation processes by exploring an innovative operational strategy that allows attaining very high ethanol titres without a critical decrease of the viability level thus minimizing the production costs due to energy savings during the distillation process.
KeywordsBio-ethanol production Industrial strain PE-2 Saccharomyces cerevisiae Repeated-batch system Very high gravity fermentation
The authors thank COPAM—Companhia Portuguesa de Amidos SA (Portugal) for kindly providing the CSL, and Rosane Schwan (Federal University of Lavras, Brazil) for kindly providing the PE-2 yeast strain. The financial support of Fundação para a Ciência e a Tecnologia (FCT), Portugal, is acknowledged: project ProBioethanol PTDC/BIO/66151/2006, grant SFRH/BD/64776/2009 to F. B. Pereira and grant SFRH/BPD/44328/2008 to P. M. R. Guimarães.
- Cahill G, Murray DM, Walsh PK, Donnelly D (2000) Effect of the concentration of propagation wort on yeast cell volume and fermentation performance. J Am Soc Brew Chem 58:14–20Google Scholar
- Mills DR (1941) Differential staining of living and dead yeast cells. Food Res 6:361–371Google Scholar
- Moonjai N, Verstrepen KJ, Delvaux FR, Derdelinckx G, Verachtert H (2002) The effect of linoleic acid supplementation of cropped yeast on its subsequent fermentation performance and acetate esters. J Inst Brew 108:227–235Google Scholar
- Ohno T, Takahashi R (1986) Role of wort aeration in the brewing process. Part 1: oxygen uptake and biosynthesis of lipid by the final yeast. J Inst Brew 92:84–87Google Scholar
- Pereira FB, Guimarães PM, Teixeira JA, Domingues L (2011) Robust industrial Saccharomyces cerevisiae strains for very high gravity bio-ethanol fermentations. J Biosci Bioeng. doi: 10.1016/j.jbiosc.2011.03.022
- van Hoek P, de Hulster E, van Dijken JP, Pronk JT (2000) Fermentative capacity in high-cell-density fed-batch cultures of baker’s yeast. Biotechnol Bioeng 68:518–523Google Scholar
- Verbelen PJ, Saerens SMG, Van Mulders SE, Delvaux F, Delvaux FR (2009a) The role of oxygen in yeast metabolism during high cell density brewery fermentations. Biotechnol Lett 82:1143–1156Google Scholar