Cellulase, Clostridia, and Ethanol

Demain, Arnold L.; Newcomb, Michael; Wu, Jiangbin

doi:10.1128/mmbr.69.1.124-154.2005

Cited by 804 publications

(611 citation statements)

References 345 publications

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“…Use of biofuels will offer several benefits, including reduced greenhouse gas emissions, decreased competition with tightening food supplies, enhanced rural economic development, and increased national energy security (Demain et al, 2005;Himmel et al, 2007;Lynd et al, 2002;Zhang et al, 2006b).…”

Section: Introductionmentioning

confidence: 99%

Comparative study of corn stover pretreated by dilute acid and cellulose solvent‐based lignocellulose fractionation: Enzymatic hydrolysis, supramolecular structure, and substrate accessibility

Zhu

Sathitsuksanoh

Vinzant

et al. 2009

Biotech & Bioengineering

198

164

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Liberation of fermentable sugars from recalcitrant biomass is among the most costly steps for emerging cellulosic ethanol production. Here we compared two pretreatment methods (dilute acid, DA, and cellulose solvent and organic solvent lignocellulose fractionation, COSLIF) for corn stover. At a high cellulase loading [15 filter paper units (FPUs) or 12.3 mg cellulase per gram of glucan], glucan digestibilities of the corn stover pretreated by DA and COSLIF were 84% at hour 72 and 97% at hour 24, respectively. At a low cellulase loading (5 FPUs per gram of glucan), digestibility remained as high as 93% at hour 24 for the COSLIF-pretreated corn stover but reached only $60% for the DA-pretreated biomass. Quantitative determinations of total substrate accessibility to cellulase (TSAC), cellulose accessibility to cellulase (CAC), and non-cellulose accessibility to cellulase (NCAC) based on adsorption of a nonhydrolytic recombinant protein TGC were measured for the first time. The COSLIF-pretreated corn stover had a CAC of 11.57 m 2 /g, nearly twice that of the DA-pretreated biomass (5.89 m 2 /g). These results, along with scanning electron microscopy images showing dramatic structural differences between the DA-and COSLIF-pretreated samples, suggest that COSLIF treatment disrupts microfibrillar structures within biomass while DA treatment mainly removes hemicellulose. Under the tested conditions COSLIF treatment breaks down lignocellulose structure more extensively than DA treatment, producing a more enzymatically reactive material with a higher CAC accompanied by faster hydrolysis rates and higher enzymatic digestibility.

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Section: Introductionmentioning

confidence: 99%

Comparative study of corn stover pretreated by dilute acid and cellulose solvent‐based lignocellulose fractionation: Enzymatic hydrolysis, supramolecular structure, and substrate accessibility

Zhu

Sathitsuksanoh

Vinzant

et al. 2009

Biotech & Bioengineering

198

164

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“…Another challenge in bacterial systems is the potential contamination with bacteriophages. An additional future option may be based on thermophilic cellulolytic Clostridia (Demain et al 2005;Lynd et al 2002). Although considerable progress has been made with respect to genetic engineering of these bacteria for homoethanolic fermentation, industrial implementation is not yet within reach.…”

Section: Introductionmentioning

confidence: 99%

Alcoholic fermentation of carbon sources in biomass hydrolysates by Saccharomyces cerevisiae: current status

Maris

Abbott

Bellissimi

et al. 2006

Antonie van Leeuwenhoek

429

276

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Fuel ethanol production from plant biomass hydrolysates by Saccharomyces cerevisiae is of great economic and environmental significance. This paper reviews the current status with respect to alcoholic fermentation of the main plant biomass-derived monosaccharides by this yeast. Wild-type S. cerevisiae strains readily ferment glucose, mannose and fructose via the Embden-Meyerhof pathway of glycolysis, while galactose is fermented via the Leloir pathway. Construction of yeast strains that efficiently convert other potentially fermentable substrates in plant biomass hydrolysates into ethanol is a major challenge in metabolic engineering. The most abundant of these compounds is xylose. Recent metabolic and evolutionary engineering studies on S. cerevisiae strains that express a fungal xylose isomerase have enabled the rapid and efficient anaerobic fermentation of this pentose.L-Arabinose fermentation, based on the expression of a prokaryotic pathway in S. cerevisiae, has also been established, but needs further optimization before it can be considered for industrial implementation. In addition to these already investigated strategies, possible approaches for metabolic engineering of galacturonic acid and rhamnose fermentation by S. cerevisiae are discussed. An emerging and major challenge is to achieve the rapid transition from proof-of-principle experiments under 'academic' conditions (synthetic media, single substrates or simple substrate mixtures, absence of toxic inhibitors) towards efficient conversion of complex industrial substrate mixtures that contain synergistically acting inhibitors.

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“…When one thinks of bacterial cellulases, the first system to come to mind is the cellulosomal system of C. thermocellum, possibly the most studied bacterial cellulase system [60,61]. Cellulosomal structures are also found in several other clostridia, including…”

Section: Clostridiummentioning

confidence: 99%

Bacterial genomes: what they teach us about cellulose degradation

Brumm

2013

Biofuels

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Cellulase, Clostridia, and Ethanol

Cited by 804 publications

References 345 publications

Comparative study of corn stover pretreated by dilute acid and cellulose solvent‐based lignocellulose fractionation: Enzymatic hydrolysis, supramolecular structure, and substrate accessibility

Comparative study of corn stover pretreated by dilute acid and cellulose solvent‐based lignocellulose fractionation: Enzymatic hydrolysis, supramolecular structure, and substrate accessibility

Alcoholic fermentation of carbon sources in biomass hydrolysates by Saccharomyces cerevisiae: current status

Bacterial genomes: what they teach us about cellulose degradation

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