Advanced Bioethanol Production Technologies: A Perspective

Himmel, Michael E.; Adney, William S.; Baker, John O.; Elander, Richard T.; McMillan, James D.; Nieves, Rafael A.; Sheehan, John; Thomas, Steven R.; Vinzant, Todd B.; Zhang, Min

doi:10.1021/bk-1997-0666.ch001

Cited by 76 publications

(35 citation statements)

References 72 publications

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“…Fuel ethanol can be produced in a sustainable way using sugars as raw material. It can also potentially be obtained at a reduced cost from agricultural residues [Aristidou and Penttilä, 2000;Himmel et al, 1997;Ingram et al, 1998]. Lignocellulosic biomass is the most abundant source of sugars , but those sugars are polymerized in the hemicellulose and cellulose fractions.…”

Section: Introductionmentioning

confidence: 99%

Specific Ethanol Production Rate in Ethanologenic <i>Escherichia coli</i> Strain KO11 Is Limited by Pyruvate Decarboxylase

Huerta-Beristain¹,

Utrilla²,

Hernández-Chávez³

et al. 2008

Microb Physiol

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Modification of ethanol productivity and yield, using mineral medium supplemented with glucose or xylose as carbon sources, was studied in ethanologenic Escherichia coli KO11 by increasing the activity of five key carbon metabolism enzymes. KO11 efficiently converted glucose or xylose to ethanol with a yield close to 100% of the theoretical maximum when growing in rich medium. However, when KO11 ferments glucose or xylose in mineral medium, the ethanol yields decreased to only 70 and 60%, respectively. An increase in GALP_Ec (permease of galactose-glucose-xylose) or PGK_Ec (phosphoglycerate kinase) activities did not change xylose or glucose and ethanol flux. However, when PDC_Zm (pyruvate decarboxylase from Zymomonas mobilis) activity was increased 7-fold, the yields of ethanol from glucose or xylose were increased to 85 and 75%, respectively, and organic acid formation rates were reduced. Furthermore, as a response to a reduction in acetate and ATP yield, and a limited PDC_Zm activity, an increase in PFK_Ec (phosphofructokinase) or PYK_Bs (pyruvate kinase from Bacillus stearothermophilus) activity drastically reduced glucose or xylose consumption and ethanol formation flux. This experimental metabolic control analysis showed that ethanol flux in KO11 is negatively controlled by phosphofructokinase and pyruvate kinase, and positively influenced by the PDC_Zm activity level.

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Section: Introductionmentioning

confidence: 99%

Specific Ethanol Production Rate in Ethanologenic <i>Escherichia coli</i> Strain KO11 Is Limited by Pyruvate Decarboxylase

Huerta-Beristain¹,

Utrilla²,

Hernández-Chávez³

et al. 2008

Microb Physiol

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“…Their sequential utilization extends fermentation times and can result in incomplete substrate consumption if products reach inhibitory levels before slowly utilized sugars are consumed (14). Moreover, cofermentation of xylose with cellobiose (Cb) could reduce enzyme costs and facilitate simultaneous saccharification and fermentation.…”

mentioning

confidence: 99%

Cofermentation of Glucose, Xylose, and Cellobiose by the Beetle-Associated Yeast Spathaspora passalidarum

Headman

et al. 2012

Appl Environ Microbiol

122

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dFermentation of cellulosic and hemicellulosic sugars from biomass could resolve food-versus-fuel conflicts inherent in the bioconversion of grains. However, the inability to coferment glucose and xylose is a major challenge to the economical use of lignocellulose as a feedstock. Simultaneous cofermentation of glucose, xylose, and cellobiose is problematic for most microbes because glucose represses utilization of the other saccharides. Surprisingly, the ascomycetous, beetle-associated yeast Spathaspora passalidarum, which ferments xylose and cellobiose natively, can also coferment these two sugars in the presence of 30 g/liter glucose. S. passalidarum simultaneously assimilates glucose and xylose aerobically, it simultaneously coferments glucose, cellobiose, and xylose with an ethanol yield of 0.42 g/g, and it has a specific ethanol production rate on xylose more than 3 times that of the corresponding rate on glucose. Moreover, an adapted strain of S. passalidarum produced 39 g/liter ethanol with a yield of 0.37 g/g sugars from a hardwood hydrolysate. Metabolome analysis of S. passalidarum before onset and during the fermentations of glucose and xylose showed that the flux of glycolytic intermediates is significantly higher on xylose than on glucose. The high affinity of its xylose reductase activities for NADH and xylose combined with allosteric activation of glycolysis probably accounts in part for its unusual capacities. These features make S. passalidarum very attractive for studying regulatory mechanisms enabling bioconversion of lignocellulosic materials by yeasts.

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“…Himmel, et al provides a comprehensive overview of recent technical progress on bioethanol. 4 As impressive as this progress has been, the price of bioethanol remains too high to compete with existing cheap sources of gasoline as a direct fuel substitute. Thus, the Biofuels Program continues to push toward a goal of producing bioethanol at prices competitive with gasoline.…”

Section: L3ackgroundmentioning

confidence: 99%

Role of Bioethanol in Global Climate Change

Sheehan¹

1998

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Advanced Bioethanol Production Technologies: A Perspective

Cited by 76 publications

References 72 publications

Specific Ethanol Production Rate in Ethanologenic <i>Escherichia coli</i> Strain KO11 Is Limited by Pyruvate Decarboxylase

Specific Ethanol Production Rate in Ethanologenic <i>Escherichia coli</i> Strain KO11 Is Limited by Pyruvate Decarboxylase

Cofermentation of Glucose, Xylose, and Cellobiose by the Beetle-Associated Yeast Spathaspora passalidarum

Role of Bioethanol in Global Climate Change

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