Ethanol fermentation of energy beets by self-flocculating and non-flocculating yeasts

Specialized varieties of sugar beets (Energy Beets™) are being developed for producing industrial sugars in Arkansas’ Mississippi River Delta. To evaluate their suitability for producing regional fermentation feedstocks, we report initial cultivation trials and ethanol fermentation of raw beet juice and combined juice with pulp mash (JPM) liquefied with enzymes, comparing ethanol yields under different regimes by self-flocculating and non-flocculating yeasts. Nine varieties produced root yields averaging 115 Mg/ha and 18.5% sucrose contents. Raw beet juice fermentation yielded ethanol up to 0.48 g/g (sugar). JPM was directly fermented through either a sequential (SeqSF) or simultaneous saccharification and fermentation (SSF) process. For both yeast types, SSF was a more efficient process than SeqSF, with ethanol yields up to 0.47 g/g (sugar) and volumetric productivity up to 7.81 g/L/h. These results indicate the self-flocculating yeast is suitable for developing efficient bioprocesses to ferment industrial sugar from energy beets.