Diferenzas entre revisións de «Lignina»

 
==Biodegradación==
A biodegradación da lignina orixinaría a destrución da madeira, especialmente nas construcións de madeira. Porén, a biodegradación da lignina é un prerrequisito para o procesamenteo de [[biofuel]] a partir de materia prima vexetal. Os modos actuais de procesamento orixinan algúns residuos problemáticos despois de procesar os contidos dixeribles ou degradables. A mellora dos modos de degradación da lignina faría que a produción fose máis eficiente.
 
A lignina é indixerible polos encimas animais, pero algúns [[fungo]]s (como o ''Polyporus squamosus'') e [[bacteria]]s poden secretar [[ligninase]]s (tamén chamadas ''lignases'') que poden degradar o polímero. Os detalles da biodegradación non se coñecen. A vía utilizada depende do tipo de pudrición da madeira realizada polos fungos. Os encimas implicados poden empregar radicais libres para as reaccións de despolimerización. <ref>{{cita libro|autor= Michael J. Carlile, Sarah C. Watkinson|título= The Fungi|editor= [[Academic Press]]|ano= 1994|isbn= 0-12-159959-0}}</ref> Encimas lignolíticos ben coñecidos son a manganeso peroxidase, lignina peroxidase e celobiosa deshidroxenase. Ademais, a causa do seus enlaces cruzados cos outros compoñentes da parede celular, a lignina minimiza a accesibilidade da celulosa e hemicelulosa aos encimas microbianos. Por tanto, en xeral a lignina está asociada coa redución da dixestibilidade do conxunto da biomasa vexetal, o cal axuda a defender as plantas contra [[patóxeno]]s e [[praga]]s.<ref name=sarkanen/>
Biodegradation of lignin would lead to destruction of wooden goods, especially buildings. However biodegradation of lignin is a prerequisite for processing [[biofuel]] from plant raw materials. Current processing setups show some problematic residuals after processing the digestible or degradable contents. The improving of lignin degradation would drive the output from biofuel processing to better gain or better efficiency factor.
 
A degradación da lignina fana fungos e bacterias. A [[lignina peroxidase]] (ou "[[ligninase]]", con [[número EC]] 1.14.99) é unha [[hemoproteína]] do fungo ''[[Phanerochaete chrysosporium]] '' que presenta varias reaccións de degradación da lignina, todas dependentes do [[peróxido de hidróxeno]] para poder incorporar osíxeno molecular nos produtos de reacción. Hai tamén outros encimas microbianos que se cre están envolvidos na biodegradación da lignina, como a manganeso peroxidase, laccase, e celobiosa deshidroxenase.
Lignin is indigestible by animal [[enzyme]]s, but some [[fungi]] (such as the [[Dryad's saddle]]) and [[bacteria]] are able to secrete [[ligninase]]s (also named ''lignases'') that can [[Biodegradation|biodegrade]] the polymer. The details of the biodegradation are not yet well understood. The pathway depends on the type of wood decay - in fungi either [[Wood-decay fungus#Brown rot|brown rot]], [[Wood-decayfungus#Soft rot|soft rot]], or [[Spalting#White_Rot|white rot]]. The enzymes involved may employ [[free radical]]s for depolymerization reactions.<ref>{{cite book|last= Carlile|first= Michael J.|coauthors= Sarah C. Watkinson|title= The Fungi|publisher= [[Academic Press]]|year= 1994|isbn= 0-12-159959-0}}</ref> Well understood lignolytic enzymes are [[manganese peroxidase]], lignin peroxidase and [[cellobiose dehydrogenase]]. Furthermore, because of its cross-linking with the other cell wall components, it minimizes the accessibility of cellulose and hemicellulose to microbial enzymes. Hence, in general lignin is associated with reduced digestibility of the overall plant biomass, which helps defend against [[pathogens]] and [[Pest (organism)|pests]].<ref name=sarkanen/>
 
Lignin-relatedOs chemicalscompostos canrelacionados becoa furtherlignina processedpoden byser bacteriaposteriormente procesados polas bacterias. ForPor instanceexemplo, thea aerobicbacteria aeróbica [[Gram-negativenegativa]] soildo bacteriumsolo ''[[Sphingomonas paucimobilis]]'' ispode abledegradar toos degradecompostos lignin-relatedquímicos biphenylbifenilo chemicalrelacionados compoundscoa lignina. <ref>[http://aem.highwire.org/cgi/content/abstract/64/7/2520 Cloning of a Sphingomonas paucimobilis SYK-6 Gene Encoding a Novel Oxygenase That Cleaves Lignin-Related Biphenyl and Characterization of the Enzyme. Xue Peng, Takashi Egashira, Kaoru Hanashiro, Eiji Masai, Seiji Nishikawa, Yoshihiro Katayama, Kazuhide Kimbara and Masao Fukuda, Appl Environ Microbiol, July 1998, p. 2520-2527, Vol. 64, No. 7]</ref>
Lignin degradation is made by micro-organisms like fungi and bacteria. [[Lignin peroxidase]] (also "[[ligninase]]", [[Enzyme Commission number|EC number]] 1.14.99) is a [[hemoprotein]] from the white-rot fungus ''[[Phanerochaete chrysosporium]] '' with a variety of lignin-degrading reactions, all dependent on [[hydrogen peroxide]] to incorporate molecular oxygen into reaction products. There are also several other microbial enzymes that are believed to be involved in lignin biodegradation, such as [[manganese peroxidase]], [[laccase]], and [[Cellobiose dehydrogenase (acceptor)]].
 
Lignin-related chemicals can be further processed by bacteria. For instance, the aerobic Gram-negative soil bacterium ''[[Sphingomonas paucimobilis]]'' is able to degrade lignin-related biphenyl chemical compounds.<ref>[http://aem.highwire.org/cgi/content/abstract/64/7/2520 Cloning of a Sphingomonas paucimobilis SYK-6 Gene Encoding a Novel Oxygenase That Cleaves Lignin-Related Biphenyl and Characterization of the Enzyme. Xue Peng, Takashi Egashira, Kaoru Hanashiro, Eiji Masai, Seiji Nishikawa, Yoshihiro Katayama, Kazuhide Kimbara and Masao Fukuda, Appl Environ Microbiol, July 1998, p. 2520-2527, Vol. 64, No. 7]</ref>
 
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