Abstract
A bench-scale unit for the development of an enzymatic process for the bioconversion of lignocellulosics to ethanol has been used to study the recycling of waste-water streams to minimize fresh-water requirements and reduce effluent streams. Willow, after impregnation with sulphur dioxide, was steam-pretreated, enzymatically hydrolysed, and the sugars produced were fermented using S. cerevisiae. The fermentation broth was distilled and the stillage was fractionated by evaporation into six separate condensate fractions and a residue. The overall yield of ethanol from willow was 65% of the theoretical yield based on total fermentable sugars. The inhibitory effect of the evaporation condensates was assessed by fermentation using S. cerevisiae. The non-volatile residue of the stillage was found to be inhibitory to fermentation. The ethanol yield decreased from 0.37 g/g in a pure sugar reference to 0.31 g/g in the residue and the average ethanol fermentation rate decreased fi om 6.3 g/(l h) to 2.7 g/(l h), respectively. The evaporation condensates, containing the volatile components, showed no negative effects on fermentation. The intermediate evaporation condensate fractions, fractions 4 and 5, had the lowest chemical oxygen demand (GOD), 1560 and 1120 mg/l, compared with 33 300 mg/l for the stillage. Therefore, these fractions can be released directly into the effluent without further treatment. Copyright (C) 1997 Elsevier Science Ltd.
Original language | English |
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Pages (from-to) | 171-179 |
Journal | Bioresource Technology |
Volume | 58 |
Issue number | 2 |
DOIs | |
Publication status | Published - 1996 |
Subject classification (UKÄ)
- Industrial Biotechnology
- Chemical Engineering
Free keywords
- ethanol production
- enzymatic process
- lignocellulosics
- willow
- steam
- treatment
- inhibitors
- waste-water recycling