14
edits
Difference between revisions of "Hydrolysis"
no edit summary
(→Enzyme) |
|||
| Line 9: | Line 9: | ||
'''Acid hydrolysis''' is a hydrolysis process in which a protic acid is used to catalyze the hydrolysis reaction. A strong acid, such as formic, hydrochloric, nitric, phosphoric, or sulphuric acid can be used in concentrated or diluted form. '''Concentrated acid''' (10-30 %) can penetrate the lignin structure and break down the cellulose and hemicellulose to individual sugars at low temperatures and high yields. Downsides are the high acid consumption and high corrosion potential. These downsides are circumvented with the use of '''diluted acid''' (2-5%). However, higher temperatures are required, which can lead to side product formation such as furfural and 5-hydroxymethyl-furfural.<ref name=":1">{{Cite book|author=Alessandra Verardi, Isabella De Bari, Emanuele Ricca and Vincenza Calabrò|year=2012|section_title=Hydrolysis of Lignocellulosic Biomass: Current Status of Processes and Technologies and Future Perspectives|editor=Marco Aurelio Pinheiro Lima and Alexandra Pardo Policastro Natalense|book_title=Bioethanol|publisher=IntechOpen}}</ref> | '''Acid hydrolysis''' is a hydrolysis process in which a protic acid is used to catalyze the hydrolysis reaction. A strong acid, such as formic, hydrochloric, nitric, phosphoric, or sulphuric acid can be used in concentrated or diluted form. '''Concentrated acid''' (10-30 %) can penetrate the lignin structure and break down the cellulose and hemicellulose to individual sugars at low temperatures and high yields. Downsides are the high acid consumption and high corrosion potential. These downsides are circumvented with the use of '''diluted acid''' (2-5%). However, higher temperatures are required, which can lead to side product formation such as furfural and 5-hydroxymethyl-furfural.<ref name=":1">{{Cite book|author=Alessandra Verardi, Isabella De Bari, Emanuele Ricca and Vincenza Calabrò|year=2012|section_title=Hydrolysis of Lignocellulosic Biomass: Current Status of Processes and Technologies and Future Perspectives|editor=Marco Aurelio Pinheiro Lima and Alexandra Pardo Policastro Natalense|book_title=Bioethanol|publisher=IntechOpen}}</ref> | ||
=== Enzyme === | === Enzyme === | ||
Enzymatic hydrolysis processes allow to produce monomeric sugars from (ligno)cellulosic biomass by using specific enzymes (i.e. cellulases and hemicellulases) able to break down the chemical bonds in cellulose and hemicellulose polymers. Several factors can affect the efficiency of this process: accessible surface area and crystallinity of the biomass, as well as pH, time and temperatures of the process<ref>{{Cite journal|title=Investigation of Enzymatic Hydrolysis of Coffee Silverskin Aimed at the Production of Butanol and Succinic Acid by Fermentative Processes|year=2019-06-01|author=Saverio Niglio, Alessandra Procentese, Maria Elena Russo, Giovanni Sannia, Antonio Marzocchella|journal=BioEnergy Research|volume=12|issue=2|page=312–324|doi=10.1007/s12155-019-09969-6 | Enzymatic hydrolysis processes allow to produce monomeric sugars from (ligno)cellulosic biomass by using specific enzymes (i.e. cellulases and hemicellulases) able to break down the chemical bonds in cellulose and hemicellulose polymers. Several factors can affect the efficiency of this process: accessible surface area and crystallinity of the biomass, as well as pH, time and temperatures of the process<ref>{{Cite journal|title=Investigation of Enzymatic Hydrolysis of Coffee Silverskin Aimed at the Production of Butanol and Succinic Acid by Fermentative Processes|year=2019-06-01|author=Saverio Niglio, Alessandra Procentese, Maria Elena Russo, Giovanni Sannia, Antonio Marzocchella|journal=BioEnergy Research|volume=12|issue=2|page=312–324|doi=10.1007/s12155-019-09969-6}}</ref>. Enzymatic hydrolysis is gaining increased attention with respect to acid hydrolysis due to equipment corrosion, energy consumption, non-recyclability of reagents, fermentation inhibitors production during acid hydrolysis<ref>{{Cite journal|title=Enzymatic hydrolysis of lignocellulosic biomass: converting food waste in valuable products|year=2015-02-01|author=Gabriela Piccolo Maitan-Alfenas, Evan Michael Visser, Valéria Monteze Guimarães|journal=Current Opinion in Food Science|volume=1|page=44–49|doi=10.1016/j.cofs.2014.10.001}}</ref>. To increase the hydrolysis efficiency, a pretreatment step prior to enzymatic reaction is usually required due to the complex lignocellulosic biomass composition ([[Primary processing]]). | ||
=== Alkali === | === Alkali === | ||
'''Alkaline hydrolysis''' refers to hydrolysis reactions using hydroxide, commonly from sodium hydroxide or calcium hydroxide. The hydroxide breaks down the lignin bonds to make the cellulose more accessible. The reaction proceeds at lower temperature and pressure and residual alkali can be recycled. However, the pretreatment does result in irrecoverable salts in the product.<ref>{{Cite journal|title=Pretreatment of lignocellulosic sugarcane leaves and tops for bioethanol production|year=2020-01-01|journal=Lignocellulosic Biomass to Liquid Biofuels|page=301–324|doi=10.1016/B978-0-12-815936-1.00010-1|author=S. Niju, M. Swathika, M. Balajii|volume=}}</ref> | '''Alkaline hydrolysis''' refers to hydrolysis reactions using hydroxide, commonly from sodium hydroxide or calcium hydroxide. The hydroxide breaks down the lignin bonds to make the cellulose more accessible. The reaction proceeds at lower temperature and pressure and residual alkali can be recycled. However, the pretreatment does result in irrecoverable salts in the product.<ref>{{Cite journal|title=Pretreatment of lignocellulosic sugarcane leaves and tops for bioethanol production|year=2020-01-01|journal=Lignocellulosic Biomass to Liquid Biofuels|page=301–324|doi=10.1016/B978-0-12-815936-1.00010-1|author=S. Niju, M. Swathika, M. Balajii|volume=}}</ref> | ||