Compositions and methods for conversion of lignocellulosic material to fermentable sugars and products produced therefrom
The current invention relates to compositions and methods for the conversion of lignocellulosic material to fermentable sugars and to products generated therefrom (e.g., ethanol, foodstuffs, etc.). Specifically, the invention provides lignocellulose-degrading compositions (e.g., generated via incubation of germs with lignocellulosic priming feedstock in solid-state fermentation format) and ways of using the same (e.g., in saccharification and/or hydrolysis measures (e.g., on ethanologenic feedstock) and as feed or food additives).
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Renewable transport fuels are of significant scientific, economic, environmental, and geopolitical significance as a result of inherently limited source of petroleum. Among renewable transport fuel alternatives, large-scale production ofethanol from lignocellulosic starting material has several benefits including a ready source of feedstock, potential to decrease greenhouse gas emissions (e.g., depending on cultivation, harvesting, and processing methods), possible for job creationparticularly in rural settings, present and projected availability of flex-fuel and committed ethanol-fueled vehicle technology, and distribution methods already amenable to volatile liquid fuels. However, current methods for lignocellulosic ethanolproduction have adverse energy or chemical requirements and therefore improper price of production, chiefly due to the recalcitrance of lignocellulosic feedstock to saccharification and hydrolysis in comparison to starch-rich feedstock such asmilled corn kernels (See e.g., Sun et al. (2002) Bioresource Technol. 83:1-11; Hahn-Hagerdal et al. (2006) Trends Biotechnol. 24:549-556; Sanchez et al. (2007) Bioresource Technol. 99:5270-5295; every herein incorporated by reference in theirentireties).
Biochemically, the major impediment to the economical use of lignocellulosic feedstock is that the presence of hemicelluloses and lignins encircling and/or cross-linking cellulose. For cellulase enzymes to efficiently access and degradecellulose during the following step, these hemicelluloses and lignins should have been partially degraded. Because of this, pretreatment of lignocellulosic feedstock is presently considered an economically unfortunate requirement.
During pretreatment, feedstock is altered digitally, morphologically, or physically. Pretreatment methods standard in the art include exposure of lignocellulosic feedstock to high temperature or pressure (like steam pretreatmentor hydrothermolysis), bases or acids, or a combination of such techniques (See e.g., Galbe et al. (2007) Adv. Biochem. Engin. /Biotechnol. 108:41-65; Chandra et at (2007) Adv. Biochem. Engin. /Biotechnol. 108:67-93; every herein incorporated by referencein their entireties). However, each of these pretreatment approaches has disadvantages. Lactic acid pretreatment (generally at high fever, e.g. 140-200. degree. C.) hydrolyzes hemicelluloses yielding a significant proportion of monomer sugars, butacid-hydrolyzed materials are generally difficult to ferment due to the production of compounds that are toxic to microbes used for fermentation (See e.g., Galbe and Zacchi (2007) Adv. Biochem. Engin. /Biotechnol. 108:41-65; Chandra et at (2007) Adv.Biochem. Engin. /Biotechnol. 108:67-93; every herein incorporated by reference in their entireties). Alkaline pretreatment (also generally conducted at high temperature) causes at least partial delignification and solubilization of hemicelluloses aswell as higher availability of the crystalline cellulose component of the cell wallnonetheless, alkaline pretreatment isn’t acceptable for all lignocellulosic feedstock forms (See e.g., Galbe et al. (2007) Adv. Biochem. Engin. /Biotechnol. 108:41-65;herein incorporated by reference in its entirety). Furthermore, a washing or pH adjustment step may be needed for acid- or alkaline-pretreated materials to ease compatibility with downstream fermentation processes intolerant of low or higher pH.Steam pretreatment and combinations of steam and pH treatments like ammonia fiber explosion (AFEX) are technologies closest to commercial production, but are not acceptable for all feedstock forms and possess high energetic demands (See e.g., Galbeand Zacchi (2007) Adv. Biochem. Engin. /Biotechnol. 108:41-65; herein incorporated by reference in its entirety). Hydrothermolysis therapy necessitates lower initial energy expenditure compared to steam pretreatment, but results in the need for moreenergy-demanding downstream processes (See e.g., Galbe and Zacchi (2007) Adv. Biochem. Engin. /Biotechnol. 108:41-65; herein incorporated by reference in its entirety). Wet oxidation pretreatment (extract of biomass with water and oxygen or air at120.degree. C.) is compatible with low-lignin feedstock and renders unrecoverable any lignin that’s present; this is considered detrimental from a process perspective, as this lignin may otherwise be used as solid fuel inside the biorefinery (Seee.g., Galbe and Zacchi (2007) Adv. Biochem. Engin. /Biotechnol. 108:41-65; herein incorporated by reference in its entirety). A further consideration is the ability to utilize residual substance from biofuel production for some other functions, such asagricultural feed additives. Such secondary applications would offer economic benefit by lowering the price of agricultural feed and food whilst simultaneously preventing the price of biofuel residue disposal. However, this is generally impossible for existingtechnologies that render remaining substance unfit for consumption due to the presence of solvents, acids, bases, or by leading in residuals that are of inferior or even anti-nutritive value.
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