Deconstruction of Lignocellulose into Soluble Sugars by Native and Designer Cellulosomes

ABSTRACT Lignocellulosic biomass, the most abundant polymer on Earth, is typically composed of three major constituents: cellulose, hemicellulose, and lignin. The crystallinity of cellulose, hydrophobicity of lignin, and encapsulation of cellulose by the lignin-hemicellulose matrix are three major f...

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Autores principales:	Sarah Moraïs, Ely Morag, Yoav Barak, Dan Goldman, Yitzhak Hadar, Raphael Lamed, Yuval Shoham, David B. Wilson, Edward A. Bayer
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Lenguaje:	EN
Publicado:	American Society for Microbiology 2012
Materias:	Microbiology QR1-502
Acceso en línea:	https://doaj.org/article/212ae9808afc4b93baf6eb4674103f9b
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spelling	oai:doaj.org-article:212ae9808afc4b93baf6eb4674103f9b2021-11-15T15:39:11ZDeconstruction of Lignocellulose into Soluble Sugars by Native and Designer Cellulosomes10.1128/mBio.00508-122150-7511https://doaj.org/article/212ae9808afc4b93baf6eb4674103f9b2012-12-01T00:00:00Zhttps://journals.asm.org/doi/10.1128/mBio.00508-12https://doaj.org/toc/2150-7511ABSTRACT Lignocellulosic biomass, the most abundant polymer on Earth, is typically composed of three major constituents: cellulose, hemicellulose, and lignin. The crystallinity of cellulose, hydrophobicity of lignin, and encapsulation of cellulose by the lignin-hemicellulose matrix are three major factors that contribute to the observed recalcitrance of lignocellulose. By means of designer cellulosome technology, we can overcome the recalcitrant properties of lignocellulosic substrates and thus increase the level of native enzymatic degradation. In this context, we have integrated six dockerin-bearing cellulases and xylanases from the highly cellulolytic bacterium, Thermobifida fusca, into a chimeric scaffoldin engineered to bear a cellulose-binding module and the appropriate matching cohesin modules. The resultant hexavalent designer cellulosome represents the most elaborate artificial enzyme composite yet constructed, and the fully functional complex achieved enhanced levels (up to 1.6-fold) of degradation of untreated wheat straw compared to those of the wild-type free enzymes. The action of these designer cellulosomes on wheat straw was 33 to 42% as efficient as the natural cellulosomes of Clostridium thermocellum. In contrast, the reduction of substrate complexity by chemical or biological pretreatment of the substrate removed the advantage of the designer cellulosomes, as the free enzymes displayed higher levels of activity, indicating that enzyme proximity between these selected enzymes was less significant on pretreated substrates. Pretreatment of the substrate caused an increase in activity for all the systems, and the native cellulosome completely converted the substrate into soluble saccharides. IMPORTANCE Cellulosic biomass is a potential alternative resource which could satisfy future demands of transportation fuel. However, overcoming the natural lignocellulose recalcitrance remains challenging. Current research and development efforts have concentrated on the efficient cellulose-degrading strategies of cellulosome-producing anaerobic bacteria. Cellulosomes are multienzyme complexes capable of converting the plant cell wall polysaccharides into soluble sugar products en route to biofuels as an alternative to fossil fuels. Using a designer cellulosome approach, we have constructed the largest form of homogeneous artificial cellulosomes reported to date, which bear a total of six different cellulases and xylanases from the highly cellulolytic bacterium Thermobifida fusca. These designer cellulosomes were comparable in size to natural cellulosomes and displayed enhanced synergistic activities compared to their free wild-type enzyme counterparts. Future efforts should be invested to improve these processes to approach or surpass the efficiency of natural cellulosomes for cost-effective production of biofuels.Sarah MoraïsEly MoragYoav BarakDan GoldmanYitzhak HadarRaphael LamedYuval ShohamDavid B. WilsonEdward A. BayerAmerican Society for MicrobiologyarticleMicrobiologyQR1-502ENmBio, Vol 3, Iss 6 (2012)
institution	DOAJ
collection	DOAJ
language	EN
topic	Microbiology QR1-502
spellingShingle	Microbiology QR1-502 Sarah Moraïs Ely Morag Yoav Barak Dan Goldman Yitzhak Hadar Raphael Lamed Yuval Shoham David B. Wilson Edward A. Bayer Deconstruction of Lignocellulose into Soluble Sugars by Native and Designer Cellulosomes
description	ABSTRACT Lignocellulosic biomass, the most abundant polymer on Earth, is typically composed of three major constituents: cellulose, hemicellulose, and lignin. The crystallinity of cellulose, hydrophobicity of lignin, and encapsulation of cellulose by the lignin-hemicellulose matrix are three major factors that contribute to the observed recalcitrance of lignocellulose. By means of designer cellulosome technology, we can overcome the recalcitrant properties of lignocellulosic substrates and thus increase the level of native enzymatic degradation. In this context, we have integrated six dockerin-bearing cellulases and xylanases from the highly cellulolytic bacterium, Thermobifida fusca, into a chimeric scaffoldin engineered to bear a cellulose-binding module and the appropriate matching cohesin modules. The resultant hexavalent designer cellulosome represents the most elaborate artificial enzyme composite yet constructed, and the fully functional complex achieved enhanced levels (up to 1.6-fold) of degradation of untreated wheat straw compared to those of the wild-type free enzymes. The action of these designer cellulosomes on wheat straw was 33 to 42% as efficient as the natural cellulosomes of Clostridium thermocellum. In contrast, the reduction of substrate complexity by chemical or biological pretreatment of the substrate removed the advantage of the designer cellulosomes, as the free enzymes displayed higher levels of activity, indicating that enzyme proximity between these selected enzymes was less significant on pretreated substrates. Pretreatment of the substrate caused an increase in activity for all the systems, and the native cellulosome completely converted the substrate into soluble saccharides. IMPORTANCE Cellulosic biomass is a potential alternative resource which could satisfy future demands of transportation fuel. However, overcoming the natural lignocellulose recalcitrance remains challenging. Current research and development efforts have concentrated on the efficient cellulose-degrading strategies of cellulosome-producing anaerobic bacteria. Cellulosomes are multienzyme complexes capable of converting the plant cell wall polysaccharides into soluble sugar products en route to biofuels as an alternative to fossil fuels. Using a designer cellulosome approach, we have constructed the largest form of homogeneous artificial cellulosomes reported to date, which bear a total of six different cellulases and xylanases from the highly cellulolytic bacterium Thermobifida fusca. These designer cellulosomes were comparable in size to natural cellulosomes and displayed enhanced synergistic activities compared to their free wild-type enzyme counterparts. Future efforts should be invested to improve these processes to approach or surpass the efficiency of natural cellulosomes for cost-effective production of biofuels.
format	article
author	Sarah Moraïs Ely Morag Yoav Barak Dan Goldman Yitzhak Hadar Raphael Lamed Yuval Shoham David B. Wilson Edward A. Bayer
author_facet	Sarah Moraïs Ely Morag Yoav Barak Dan Goldman Yitzhak Hadar Raphael Lamed Yuval Shoham David B. Wilson Edward A. Bayer
author_sort	Sarah Moraïs
title	Deconstruction of Lignocellulose into Soluble Sugars by Native and Designer Cellulosomes
title_short	Deconstruction of Lignocellulose into Soluble Sugars by Native and Designer Cellulosomes
title_full	Deconstruction of Lignocellulose into Soluble Sugars by Native and Designer Cellulosomes
title_fullStr	Deconstruction of Lignocellulose into Soluble Sugars by Native and Designer Cellulosomes
title_full_unstemmed	Deconstruction of Lignocellulose into Soluble Sugars by Native and Designer Cellulosomes
title_sort	deconstruction of lignocellulose into soluble sugars by native and designer cellulosomes
publisher	American Society for Microbiology
publishDate	2012
url	https://doaj.org/article/212ae9808afc4b93baf6eb4674103f9b
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Deconstruction of Lignocellulose into Soluble Sugars by Native and Designer Cellulosomes

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