Saccharomyces cerevisiae pentose fermentation

The fermentation inhibitors include furan aldehydes, aliphatic acids, and phenolic compounds. The furan aldehydes, furfural, and hydroxymethyl furfural (HMF), are formed from pentoses and hexoses, respectively (4,5). Several studies indicate that furfural inhibits Saccharomyces cerevisiae, at least when present in high concentrations (6-10). HMF has a similar effect (11,12). 

Index Entries Bioethanol corn fiber oil Escherichia coli pentose fermentations Saccharomyces cerevisiae p-glucosidase. 

The yeast (Saccharomyces cerevisiae) enzymes are specific to six-carbon sugars, but wood and other forms of biomass also contain large quantities of pentose sugars, especially xylose in hardwoods. The pentoses are not fermentable to ethyl alcohol with conventional yeasts. However, researchers at the U.S.D.A. 

Johansson, B., Hahn-Gaegerdal, B. (2002). The non-oxidative pentose phosphate pathway controls the fermentation rate of xylulose, but not of xylose in Saccharomyces cerevisiae. FEMS Yeast Research, 2, 211 282. 

Verho, R., Londesborough, J., Penttilae, M., Richard, P. (2003). Engineering redox cofactor regeneration for improved pentose fermentation in Saccharomyces cerevisiae. Applied and Environmental Microbiology, 69(10), 5892-5897. 

Genetically Modified Organisms. Traditionally, Saccharomyces cerevisiae is used in industrial ethanol fermentation however, S. cerevisiae is not able to utilize pentoses, which present a significant fraction of the sugars present in lignocellulosic material. 

Some organisms, such as Zymomonas mohilis and Saccharomyces cerevisiae, are naturally able to produce ethanol as their major fermentation product. However, these two ethanologenic organisms are not naturally capable of using the pentose... 

Bettiga M, Bengtsson O, Hahn-Hagerdal B, Gorwa-Grausiund MF (2009) Arabinose and xylose fermentation by recombinant Saccharomyces cerevisiae expressing a fungal pentose utilization pathway. Microb Cell Fact 8(1) 40... 

Bioethanol is produced from the hydrolysate of lignocellulosic substrate after pretreatment and enzymatic hydrolysis. With high conversion of carbohydrates, hexose and pentose can be fermented by commercial or engineered Saccharomyces cerevisiae or other microorganisms. Depending on the feedstock and pretreatment processes, various types of growth-inhibiting compounds have been discovered to hinder the performance of fermentation. For example, HMF and furfural formed from dehydration of... 

As described by Vaughan-Martini and Martini (1998a), Saccharomyces appear microscopically as globose or ovoidal cells with multilateral budding and possibly pseudohyphae (Fig. 1.4). The yeast forms one to four ascospores, which are smooth and ellipsoidal. Colonies appear smooth, usually flat, and occasionally raised and opaque. The two primary species found in wines, S. bay anus and S. cerevisiae (anamorph Candida robusta), ferment glucose, sucrose, and raffinose and assimilate glucose, sucrose, maltose, raffinose, and ethanol but not nitrate. Saccharomyces can not utilize five-carbon sugars (e.g., pentoses). 

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