期刊
FERMENTATION-BASEL
卷 7, 期 4, 页码 -出版社
MDPI
DOI: 10.3390/fermentation7040288
关键词
second-generation bioethanol; softwood hydrolysate; Saccharomyces cerevisiae; automated propagation strategy; non-fermentable carbon sources; C5; C6 co-consumption; xylose
Propagating yeast on non-fermentable carbon sources can enhance xylose metabolism and improve efficiency in xylose fermentation.
An economically viable production of second-generation bioethanol by recombinant xylose-fermenting Saccharomyces cerevisiae requires higher xylose fermentation rates and improved glucose-xylose co-consumption. Moreover, xylose-fermenting S. cerevisiae recognises xylose as a non-fermentable rather than a fermentable carbon source, which might partly explain why xylose is not fermented into ethanol as efficiently as glucose. This study proposes propagating S. cerevisiae on non-fermentable carbon sources to enhance xylose metabolism during fermentation. When compared to yeast grown on sucrose, cells propagated on a mix of ethanol and glycerol in shake flasks showed up to 50% higher xylose utilisation rate (in a defined xylose medium) and a double maximum fermentation rate, together with an improved C5/C6 co-consumption (on an industrial softwood hydrolysate). Based on these results, an automated propagation protocol was developed, using a fed-batch approach and the respiratory quotient to guide the ethanol and glycerol-containing feed. This successfully produced 71.29 +/- 0.91 g/L yeast with an average productivity of 1.03 +/- 0.05 g/L/h. These empirical findings provide the basis for the design of a simple, yet effective yeast production strategy to be used in the second-generation bioethanol industry for increased fermentation efficiency.
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