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Techniques for the Evolution of Robust Pentose-fermenting Yeast for Bioconversion of Lignocellulose to Ethanol
Published on: October 24, 2016
Bioconversion of brewer's spent grains to bioethanol
Jane S White1, Biju K Yohannan, Graeme M Walker
1Yeast Research Group, School of Contemporary Science, University of Abertay, Dundee, Scotland, UK.
FEMS Yeast Research
|June 13, 2008
Summary
Spent grains, a brewing byproduct, can be converted into sugars for fuel ethanol production. Acid and enzyme treatments effectively released sugars, but yeast fermentation yielded lower ethanol due to inhibitory compounds.
Area of Science:
- Biotechnology
- Biomass Conversion
- Renewable Energy
Background:
- Spent grains (SG) are a significant lignocellulosic byproduct of the brewing industry.
- SG presents a potential feedstock for biofuel production, specifically fuel ethanol.
Purpose of the Study:
- To develop and optimize methods for converting SG into fermentable sugars.
- To evaluate the efficiency of SG hydrolysate fermentation into ethanol by selected yeast strains.
Main Methods:
- Spent grains were pretreated using dilute nitric acid (0.16 N HNO3) at 121°C for 15 minutes.
- Enzymatic hydrolysis with cellulase and hemicellulase preparations was employed to release sugars.
- Fermentation trials were conducted using Pichia stipitis and Kluyveromyces marxianus.
Main Results:
- Optimized pretreatment and enzymatic digestion yielded 40-48 g of reducing sugars per 100 g of SG.
- The hydrolysate contained significant concentrations of glucose (27 g/L), xylose (16.7 g/L), and arabinose (11.9 g/L).
- Ethanol yields of 8.3 g/L and 5.9 g/L were achieved with P. stipitis and K. marxianus, respectively.
Conclusions:
- Dilute acid and enzymatic pretreatment is a viable strategy for converting spent grains into fermentable sugars.
- The presence of inhibitory compounds in the spent grain hydrolysate impacted yeast fermentation efficiency.
- Further research is needed to mitigate inhibitors for improved ethanol yields from spent grains.
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