Co-fermentation of glucose, xylose and/or cellobiose by yeast
Inventors
Jeffries, Thomas W. • Willis, Laura B. • Long, Tanya M. • Su, Yi-Kai
Assignees
US Department of Agriculture USDA • Wisconsin Alumni Research Foundation
Publication Number
US-8530211-B2
Publication Date
2013-09-10
Expiration Date
2032-04-19
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Abstract
Provided herein are methods of using yeast cells to produce ethanol by contacting a mixture comprising xylose with a Spathaspora yeast cell under conditions suitable to allow the yeast to ferment at least a portion of the xylose to ethanol. The methods allow for efficient ethanol production from hydrolysates derived from lignocellulosic material and sugar mixtures including at least xylose and glucose or xylose, glucose and cellobiose.
Core Innovation
The invention provides methods of using yeast cells, specifically Spathaspora passalidarum, to produce ethanol by fermenting mixtures comprising xylose, glucose, and optionally cellobiose under conditions suitable to allow fermentation of at least a portion of the sugars to ethanol. These methods enable efficient ethanol production from hydrolysates derived from lignocellulosic materials and sugar mixtures including xylose and glucose or xylose, glucose, and cellobiose.
The problem addressed is the limitation of current ethanol production methods that rely on starch or sucrose feedstocks, which compete with food supplies and cause ecological damage. Additionally, existing yeasts and bacteria engineered for ethanol production from xylose or other sugars suffer from drawbacks such as low production rates, glucose repression of utilization of other sugars, susceptibility to inhibitors, and regulatory issues. There is a need for yeasts capable of fermenting glucose, xylose, cellobiose, and other sugars from lignocellulosic materials at high rates and yields without these drawbacks.
Claims Coverage
The patent contains multiple claims focusing on a method for ethanol production using Spathaspora passalidarum yeast strains, including adaptations and specific fermentation conditions. The main inventive features cover the yeast strain used, substrate mixtures, fermentation conditions, and adaptations for improved performance.
Use of Spathaspora passalidarum NN245 for co-fermentation of xylose and glucose
A method of producing ethanol by contacting a mixture comprising xylose and glucose with Spathaspora passalidarum yeast strain NN245 under conditions allowing fermentation of xylose either before or during glucose fermentation.
Adaptation of yeast for hydrolysate growth
Use of Spathaspora passalidarum yeast adapted for growth in hydrolysates to improve fermentation performance.
Control of glucose concentration in mixture
Fermentation performed with glucose concentration less than or equal to about 30 g/l in the mixture.
Fermentation of cellobiose in mixtures
Method includes fermentation of mixtures that further comprise cellobiose, with conditions suitable for fermenting at least a portion of cellobiose to ethanol.
Oxygen limitation during fermentation
Fermentation under oxygen-limiting conditions with oxygen concentration less than or equal to about 2.1% in the mixture to enhance ethanol production.
Use of hydrolysates from specific biomass sources
The mixture fermented can be a hydrolysate derived from various biomass sources including corn stover, grain hulls, wood types, grasses, and other listed plants.
Adaptation to acidic hydrolysates and acetic acid tolerance
Yeast adapted to growth in acidic hydrolysates, including tolerance to at least 3.0 g/l acetic acid, prior to fermentation.
Ethanol production rate and yield parameters
The method achieves an ethanol production rate greater than or equal to about 0.5 g/l·h and ethanol yield greater than or equal to about 0.3 grams ethanol per gram sugar consumed.
The claims cover a method using the specific yeast strain Spathaspora passalidarum NN245 and its adapted forms to ferment mixtures containing xylose, glucose, and optionally cellobiose under controlled oxygen-limiting conditions from hydrolysates of lignocellulosic biomass, achieving efficient ethanol production rates and yields.
Stated Advantages
Efficient fermentation of xylose and cellobiose in the presence of glucose, overcoming glucose repression issues seen in other yeasts.
Capability to ferment sugar mixtures derived from lignocellulosic hydrolysates, enabling renewable fuel production from non-food biomass.
Yeast strains have minimal growth and nutrient requirements suitable for minimal media, lowering production costs.
Adapted yeast strains show improved tolerance to inhibitors such as acetic acid and better fermentation performance in hydrolysate media.
High ethanol yields (at least about 0.30 g ethanol per gram sugar) and production rates (at least about 0.5 g/l·h) under controlled oxygen limitation.
Documented Applications
Production of ethanol from hydrolysates derived from lignocellulosic material including agricultural residues, hardwoods, grasses, and other biomass sources.
Industrial fermentation in bioreactors ranging from 1 liter to 1,000,000 liters to produce ethanol from mixtures of glucose, xylose, and cellobiose.
Use in renewable fuel production from biomass feedstocks that do not compete with food supplies.
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