Hemicelluloses as structure regulators in the aggregation of native cellulose

Atalla, Rajai H.; Hackney, J. M.; Uhlin, I.; Thompson, Norman S.

doi:10.1016/0141-8130(93)90007-9

Cited by 156 publications

(88 citation statements)

References 4 publications

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“…In vitro reconstitution studies of XG and cellulose have shown that XG binds efficiently to cellulose even in the presence of other cell wall ~-glucans, arabinogalactans and pectins (Hayashi et al, 1987). It has also been shown that XG can compete successfully with the glucan chains of cellulose for binding since, when present in the culture medium, it leads to the formation of smaller-diameter Acetobacter cellulose microfibrils (Atalla et al, 1993). The cross-linking of cellulose by bound XG has also been inferred from electron microscope images of chelator and mild alkali-extracted cell walls (McCann et aL, 1990(McCann et aL, , 1992 and of artificially assembled bacterial cellulose-XG composites (Whitney etal., 1995).…”

Section: Introductionmentioning

confidence: 99%

Xyloglucan sidechains modulate binding to cellulose during in vitro binding assays as predicted by conformational dynamics simulations

1997

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SummaryCross-links between cellulose microfibrils and xyloglucan (XG) molecules play a major role in defining the structural properties of plant cell walls and the regulation of growth and development of dicotyledonous plants. How these cross-links are established and how they are regulated has yet to be determined. In a previous study, preliminary data were presented which suggested that the different sidechains of XG may play a role in controlling cellulose microfibriI-XG interactions. In this study, this question is addressed directly by analyzing to what extent the different sidechains of pea cell wall XG and nasturtium seed storage XG affect their binding to cellulose microfibrils. Of particular importance to this study are the chemical data indicating that pea XG possesses a trisaccharide sidechain, which is not found in nasturtium XG. To this end, conformational dynamic simulations have been used to predict whether oligosaccharides representative of pea and nasturtium XG can adopt a hypothesized cellulosebinding conformation and which of these XGs exhibits a preferential ability to bind cellulose. Extensive analysis of the conformational forms populated during 300 K and high-temperature Monte Carlo simulations established that a planar, sterically accessible, glucan backbone is essential for optimal cellulose-binding. For the trisaccharide sidechain-containing oligosaccharide as found in pea XG, sidechain orientation appeared to regulate the gradual acquisition of this hypothesized cellulose binding conformation. Thus, conformational forms were identified that included the twisted backbone (non-planar) putative solution form of XG, forms in which the trisaccharide sidechain orientation enables increased backbone planarity and steric accessibility, and finally a planar, sterically accessible, backbone. By applying these conformational requirements for cellulose binding, it has been Received 25 May 1996; revised 11 October 1996; accepted 12 November 1996. *For correspondence (fax +1 303 492 7744; e-mail levy@spot.colorado.edu).determined that pea XG possesses a two-to threefold occurrence of the cellulose binding conformation than nasturtium XG. Based on this finding, it was predicted that pea XG would bind to cellulose at a higher rate than nasturtium XG. In vitro binding assays showed that pea XG-avicel binding does indeed occur at a twofold higher rate than nasturtium XG-avicel binding. The enhanced ability of pea cell wall XG over nasturtium seed storage XG to associate with cellulose is consistent with a structural role of the former during epicotyl growth where efficient association with cellulose is a requirement. In contrast, the relatively low ability of nasturtium XG to bind cellulose is consistent with the need to enhance the accessibility of this polymer to glycanases during germination. These findings suggest potential roles for XG sidechain substitution, enabling XG to function in a variety of different biological contexts.

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Section: Introductionmentioning

confidence: 99%

Xyloglucan sidechains modulate binding to cellulose during in vitro binding assays as predicted by conformational dynamics simulations

1997

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“…The hemicelluloses are thought to act as a viscous matrix in which the fibrils are embedded and to provide a mechanically favorable 'stick-slip' mechanism when the fibre is loaded beyond elastic deformation (Fratzl et al 2004a, b;Keckes et al 2003). Copolymerisation experiments with bacterial cellulose (Atalla et al 1993;Tokoh et al 2002;Whitney et al 1998Whitney et al , 1999Whitney et al , 1995 and studies on the polymerization of lignin (Chen and Sarkanen 2003;Lewis et al 1999) also suggest an important role of the hemicelluloses for the structure of lignin and the formation of cellulose aggregates. In spruce wood, two kinds of hemicelluloses, xylan and glucomannan, are believed to be preferentially linked to lignin and cellulose respectively Salmén 2003, 2005;Olsson and Salmén 1992;Salmén 2004Salmén , 1998.…”

Section: Introductionmentioning

confidence: 99%

The implication of chemical extraction treatments on the cell wall nanostructure of softwood

et al. 2007

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Spruce wood was subjected to welldefined extraction treatments with sodium chlorite (NaClO 2 ) for delignification, as well as with sodium hydroxide (NaOH) at different concentrations for extraction of hemicelluloses. The corresponding changes of the macromolecular polymer assembly were investigated by small-angle X-ray scattering (SAXS). Measurements with Fourier-transform infrared (FTIR) spectroscopy and wide-angle scattering (WAXS) gave qualitative information about the effectiveness of the extraction process, while the scattering experiments provided information about the regularity and typical dimensions of the molecular structures. The scattering data indicated that delignification had only a moderate effect on the structural organisation of the cell wall, while further extraction with NaOH induced considerable nanostructural changes.

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“…Estes agregados conferem elevada resistência à tensão, tornando a celulose insolúvel em água e em um grande número de outros solventes. 18,19 As estrutura apresenta ramificações que interagem facilmente com a celulose, dando estabilidade e flexibilidade ao agregado. 20 Comparadas com a celulose, as hemiceluloses apresentam maior susceptibilidade à hidrólise ácida, pois oferecem uma maior acessibilidade aos ácidos minerais comumente utilizados como catalisadores.…”

Section: Características Estruturais Da Biomassa Lignocelulósicaunclassified

“…A produção de energia baseada na matriz lignocelulósica é uma importante rota alternativa que vem sendo mundialmente estudada. 18,39 O interesse pela otimização na obtenção do etanol de celulose vem crescendo muito, conforme já mencionado, em consequência de a celulose corresponder à substância de maior concentração na biomassa e por apresentar uma alta eficiência para produção de etanol quando submetido a reações de hidrólise. 16 A complexa estrutura da parede celular da biomassa lignoceluló-sica, no geral, é resistente à bioconversão.…”

Section: Recalcitrância Da Biomassa Lignocelulósica Da Cana-de-açúcarunclassified

Potencial da palha de cana-de-açúcar para produção de etanol

Santos¹,

Queiróz²,

Colodette³

et al. 2012

Quím. Nova

217

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Recebido em 26/4/11; aceito em 11/11/11; publicado na web em 13/1/12 POTENTIAL OF SUGARCANE STRAW FOR ETHANOL PRODUCTION. Sugarcane straw biomass accounts for 1/3 of the energy potential of sugarcane and represents a rich source of sugars. Studies have been intensified for the use of this biomass along with bagasse for the production of cellulosic ethanol. Development of this technological path will allow for taking full advantage of sugarcane, increasing ethanol production without expanding the area cultivated. However, in order for this technology to be viable certain challenges must be overcome, including establishment of appropriate conditions of pretreatment and hydrolysis of these materials for release of fermentable sugars.Keywords: sugarcane straw; lignocelullosic biomass; ethanol. INTRODUÇÃOA iminente escassez das reservas de petróleo, principal fonte energética mundial, juntamente com as preocupações da sociedade com a preservação ambiental, são os principais motivos que levaram os governos a buscarem estratégias para uma maior produção e maior consumo de combustíveis que sejam renováveis e sustentáveis. 1,2 Um dos principais objetivos do uso dos biocombustíveis é a substituição de combustíveis fósseis, permitindo a diminuição da dependência por recursos não renováveis e a redução das emissões de gases de efeito estufa. A queima de combustíveis fósseis representa aproximadamente 82% das emissões dos gases causadores do efeito estufa. 3 Portanto, seja pela questão ambiental global, seja pela importância em reduzir a dependência externa de energia, o etanol de cana-de-açúcar, que já apresenta indicadores ambientais muito positivos quando comparado a outras opções, representa uma alternativa viável na substituição de combustíveis fósseis. 4 O etanol obtido do caldo de cana-de-açúcar (etanol de primeira geração) é, até o momento, o único combustível com capacidade de atender à crescente demanda mundial por energia renovável de baixo custo e de baixo poder poluente. Deve-se considerar que as emissões gasosas com a queima do etanol são da ordem de 60% menores se comparadas às emissões da queima da gasolina, sendo ainda que o do CO 2 emitido é reabsorvido pela própria cana. 5 Atualmente, o etanol é produzido praticamente a partir de matérias-primas sacarinas ou amiláceas, cana-de-açúcar e milho, respectivamente. Entretanto, há um grande esforço da comunidade científica para o desenvolvimento de novos processos economicamente viáveis para o aproveitamento da componente lignocelulósica da biomassa, caso dos resíduos agrícolas (palha e bagaço de cana-de--açúcar, palha de trigo e resíduos de milho) e resíduos florestais (pó e restos de madeira), assim como o capim elefante para produção de etanol combustível (etanol de segunda geração). 6,7 O mais abundante recurso biológico renovável da terra é a biomassa lignocelulósica. 8 Estima-se que somente os EUA têm potencial para produzir mais de 1,3 bilhões de toneladas (base seca) de biomassa por ano. 9 Segundo Zhang, 10 um bilhão de toneladas de biomassa seca produz e...

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Hemicelluloses as structure regulators in the aggregation of native cellulose

Cited by 156 publications

References 4 publications

Xyloglucan sidechains modulate binding to cellulose during in vitro binding assays as predicted by conformational dynamics simulations

Xyloglucan sidechains modulate binding to cellulose during in vitro binding assays as predicted by conformational dynamics simulations

The implication of chemical extraction treatments on the cell wall nanostructure of softwood

Potencial da palha de cana-de-açúcar para produção de etanol

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