Category Archives: Biofuel Technologies

Physical Pretreatments

Changing the structure of biomass, typically increasing the enzyme accessible surface area, and reducing the degrees of polymerization of biomass, are possible by physical pretreatments such as size reduction (Zhu and Pan 2010; Harun et al. 2011). Different types of milling (e. g., ball milling, hammer milling, colloid milling, two-roll milling, and vibro energy milling), irradiations (e. g., by micro­waves, […]

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Hydrogen Peroxide-Producing Enzymes

Fungi, white-rot basidiomycetes in particular, require H2O2 to allow the extra­cellular peroxidase enzymes to function in lignin degradation. The H2O2 is pro­vided by oxidases that are produced by the fungus and act by reducing molecular O2 to H2O2 alongside the oxidation of a co-substrate (Dashtban et al. 2009; Isroi et al. 2011). Two such oxidases are glyoxal oxidase (GLOX; EC […]

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Ethanol from Starch

Starch is a one of the best and most high yielding feedstock for ethanol production, but yeast S. cereviciae cannot utilize it directly. Hydrolysis is required to produce ethanol from starch by fermentation. Starch was traditionally hydrolyzed by acids, but the specificity of the enzymes, their inherent mild reaction conditions, and the absence of secondary reactions have made the amylases […]

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Other Environmental Impacts

Apart from life-cycle GHG emissions, Table 2.3 shows the other three environ­mental impact potentials including acidification potential (AP) which is expressed as g SO2 eq., eutrophication potential (EP) which is measured in g PO3 eq., and photochemical ozone creation potential (POCP) is measured relative to ethylene as expressed in g C2H4 eq. which is determined based on the impact potential […]

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Plant Cell Wall

Lignocellulosic biomass refers to plant biomass. All plant cells are surrounded by an extracellular matrix known as the cell wall, a polysaccharide-rich matrix which is a major component of terrestrial plants. The plant cell wall is a composite structure and is divided into three layers; the middle lamella, the primary wall and the secondary wall (Carpita and Gibeaut 1993; Somerville […]

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Operating at High Solid Content

Operating at high solid content in the enzymatic hydrolysis process is crucial for large-scale development of bioproduct and biofuel production processes. The aim of utilizing high solid content is to reach high sugar concentrations and subse­quently high concentrations of fermentation products, such as ethanol (Jprgensen et al. 2007a; Hodge et al. 2009). Furthermore, maintaining high substrate con­centrations throughout the conversion […]

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Lignin

Lignin, a very complex polymer, playing a cementing role to connect cells, increases the mechanical strength properties, and makes plant resistant against diseases and biodegradation by microorganisms. Lignin is sometimes referred as glue between hemicellulose and cellulose components; while sometimes the hemicellulose is referred as glue between lignin and cellulose. Anyway, hemi — cellulose and lignin are known to cover […]

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Scanning Electron Microscopy

A scanning electron microscope (SEM) is an electron microscope that images a sample by scanning it with a beam of electrons in a raster scan pattern. The electrons bombard the atoms of the sample and the signal produced reflects information about the sample’s surface topography, composition and other prop­erties such as electrical conductivity.

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Engineering Product Forming Ability into Biomass Degraders

Several species of cellulolytic fungi, such as Trichoderma reesei, naturally pro­duce a large repertoire of saccharolytic enzymes to digest lignocellulose effi­ciently, assimilate all lignocellulosic sugars, and convert these sugars into ethanol, showing that they naturally possess all pathways for conversion of lignocellulose into bioethanol (Chambergo et al. 2002; Lynd et al. 2002). It has been shown that a biorefinery consuming […]

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Chemical Pretreatments

Chemical pretreatment is treatment of the lignocelluloses using chemicals to modify the crystalline structure of cellulose and remove and/or modify hemicel — luloses and lignin (Taherzadeh and Karimi 2008; Zhu and Pan 2010). There are several reviews and chapter books which present and compare chemical pre­treatments (McMillan 1994; Wyman 1996; Galbe and Zacchi 2007; Taherzadeh and Karimi 2008; Alvira et […]

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