Effects of biotic and abiotic factors on ethanol concentration in stored sugarbeet roots.

BACKGROUND: Ethanol is a common contaminant in sugarbeet factories that is believed to be produced by fermentation of sucrose by microbes present in the factory. Ethanol, however, may also enter factory processing streams as a contaminant in delivered sugarbeet roots, although no studies have examined whether harvested and stored roots contain ethanol or evaluated factors that might affect ethanol accumulation in postharvest roots. Research was conducted to determine the capability and extent to which sugarbeet roots produce and accumulate ethanol following harvest and determine the effects of storage temperature, duration, ventilation, and rots on root ethanol concentration.

RESULTS: Harvested and stored sugarbeet roots contained the gene transcripts and enzymatic activities required for fermentation and accumulated ethanol at concentrations of 300 to 900 ppm. Root ethanol concentrations were unaffected by storage temperature or duration during 90 days storage at 5, 12, or 20 °C and were unaffected by reductions in root ventilation that lowered oxygen concentrations by 32%. However, the fungal pathogens, Botrytis cinerea and Penicillium vulpinum, and the opportunistic bacterium, Leuconostoc suionicum, significantly increased ethanol concentration in rotted root tissues.

CONCLUSION: Sugarbeet roots delivered to factories contain ethanol and contribute to ethanol in factory processing streams. Results indicate that healthy roots constitutively produce ethanol at low levels and that storage diseases significantly elevate root ethanol concentrations. Efforts to reduce postharvest sucrose loss due to fermentation, therefore, should consider not only fermentation by microbes in the factory, but also fermentation within harvested and stored roots. Published 2025. This article is a U.S. Government work and is in the public domain in the USA.