Dekkera/Brettanomyces yeasts for ethanol production from renewable sources under oxygen-limited and low-pH conditions |
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Authors: | Galafassi Silvia Merico Annamaria Pizza Francesca Hellborg Linda Molinari Francesco Pikur Jure Compagno Concetta |
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Institution: | 1.Dipartimento di Scienze Biomolecolari e Biotecnologie, Università degli Studi di Milano, via Celoria 26, 20133, Milan, Italy ;2.Cell and Organism Biology, Lund University, Sölvegatan 35, 22362, Lund, Sweden ;3.Dipartimento di Scienze e Tecnologie Alimentari e Microbiologiche, Università degli Studi di Milano, via Celoria 2, 20133, Milan, Italy ; |
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Abstract: | Industrial fermentation of lignocellulosic hydrolysates to ethanol requires microorganisms able to utilise a broad range of
carbon sources and generate ethanol at high yield and productivity. D. bruxellensis has recently been reported to contaminate commercial ethanol processes, where it competes with Saccharomyces cerevisiae 4, 26]. In this work Brettanomyces/Dekkera yeasts were studied to explore their potential to produce ethanol from renewable sources under conditions suitable for industrial
processes, such as oxygen-limited and low-pH conditions. Over 50 strains were analysed for their ability to utilise a variety
of carbon sources, and some strains grew on cellobiose and pentoses. Two strains of D. bruxellensis were able to produce ethanol at high yield (0.44 g g−1 glucose), comparable to those reported for S. cerevisiae. B. naardenensis was shown to be able to produce ethanol from xylose. To obtain ethanol from synthetic lignocellulosic hydrolysates we developed
a two-step fermentation strategy: the first step under aerobic conditions for fast production of biomass from mixtures of
hexoses and pentoses, followed by a second step under oxygen limitation to promote ethanol production. Under these conditions
we obtained biomass and ethanol production on synthetic lignocellulosic hydrolysates, with ethanol yields ranging from 0.2
to 0.3 g g−1 sugar. Hexoses, xylose and arabinose were consumed at the end of the process, resulting in 13 g l−1 of ethanol, even in the presence of furfural. Our studies showed that Brettanomyces/Dekkera yeasts have clear potential for further development for industrial processes aimed at production of ethanol from renewable
sources. |
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