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Difference between revisions of "Hydrolysis"
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=== Origin and composition === | === Origin and composition === | ||
Hydrolysis can be performed as a pretreatment on any biowaste with a high lignocellulose content. Lignocellulose is typically the nonedible part of a plant, composed of a complex of cellulose, hemi-cellulose and lignin. | Hydrolysis can be performed as a pretreatment on any biowaste with a high lignocellulose content. Lignocellulose is typically the nonedible part of a plant, composed of a complex of cellulose, hemi-cellulose and lignin. Suitable feedstocks include grasses, straw, leaves, stems, shells, manure, paper waste, and others. The ratio between cellulose, hemi-cellulose and lignin varies wildly depending on the specific feedstock.<ref name=":1" /> | ||
=== Pre-treatment === | === Pre-treatment === | ||
* [[Sizing]] | * [[Sizing]] | ||
* | |||
== Process and technologies == | == Process and technologies == | ||
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=== Subcritical water === | === Subcritical water === | ||
Subcritical water hydrolysis (SWH) can also be called h''ydrothermal liquefaction'', ''hydrothermolysis'', or ''aquathermolysis''. The technique uses water at high temperatures and pressures to keep it in a liquid form. SWH can reduce reaction time and thereby degradation product formation, generates less waste water and lower corrosion requirements.<ref>{{Cite journal|title=Subcritical water hydrolysis of sugarcane bagasse: An approach on solid residues characterization|year=2016-02-01|author=D. Lachos-Perez, F. Martinez-Jimenez, C. A. Rezende, G. Tompsett, M. Timko, T. Forster-Carneiro|journal=The Journal of Supercritical Fluids|volume=108|page=69–78|doi=10.1016/j.supflu.2015.10.019}}</ref> | Subcritical water hydrolysis (SWH) can also be called h''ydrothermal liquefaction'', ''hydrothermolysis'', or ''aquathermolysis''. The technique uses water at high temperatures and pressures to keep it in a liquid form. SWH can reduce reaction time and thereby degradation product formation, generates less waste water and lower corrosion requirements.<ref>{{Cite journal|title=Subcritical water hydrolysis of sugarcane bagasse: An approach on solid residues characterization|year=2016-02-01|author=D. Lachos-Perez, F. Martinez-Jimenez, C. A. Rezende, G. Tompsett, M. Timko, T. Forster-Carneiro|journal=The Journal of Supercritical Fluids|volume=108|page=69–78|doi=10.1016/j.supflu.2015.10.019}}</ref> | ||
=== Enzymatic hydrolysis === | |||
Enzymatic hydrolysis is a catalytic decomposition of a chemical compound by reaction with water, such as the conversion of lignocellulosic materials, by the addition of specific enzymes. | |||
However, the hydrolysis of native lignocellulosic material is slow and is primarily governed by their structural features, since: | |||
1. cellulose present in biomass possesses highly resistant crystalline structure; | |||
2. lignin surrounding the cellulose forms a physical barrier; | |||
3. The sites available for enzymatic attack are limited. | |||
The cellulose present in lignocellulosic materials is composed of crystalline and amorphous components. The amorphous component is more susceptible to enzymatic attack than the crystalline component. The presence of lignin forms a physical barrier for enzymatic attack; therefore, treatments causing disruption of the lignin seal will increase the accessibility of cellulose to enzyme molecules and eventually its hydrolysis rate. The limitation of available sites for enzymatic attack stems from the fact that the average size of the capillaries in biomass is too small to allow the entry of large enzyme molecules; and thus, enzymatic attack is confined to the external surface [10]. | |||
Pretreatment, therefore, is an essential prerequisite to enhance the susceptibility of lignocellulosic materilas to enzyme action. An ideal pretreatment would accomplish reduction in lignin content, concommitant with a reduction in crystallinity, and an increase in surface area. The variety of pretreatments can be classified into physical, chemical, and biological depending on the mode of their action [10]. | |||
== Product == | == Product == | ||
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== References == | == References == | ||
<references /> | <references />10. ''The Nature of Lignocellulosics and Their Pretreatments for Enzymatic Hydrolysis L. T. Fan, Young-Hyun Lee and M. M. Gharpuray Department of Chemical Engineering Kansas State University Manhattan, KS 66506/U.S.A.'' | ||
[[Category:Primary processing]] | [[Category:Primary processing]] | ||