An Overview of Factors Influencing the Enzymatic Hydrolysis of Lignocellulosic Feedstocks

Esteghlalian, Ali R.; Srivastava, Vinit; Gilkes, Neil R.; Gregg, David J.; Saddler, John N.

doi:10.1021/bk-2001-0769.ch006

Cited by 38 publications

(33 citation statements)

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“…Esteghlalian et al [31] reported similar kinetic behavior, although other investigators have reported that temperature has little effect on maximum xylose yields [32,33].…”

Section: Acid-catalyzed Prehydrolysis/pretreatmentmentioning

confidence: 84%

Continuous biomass fractionation process for producing ethanol and low‐molecular‐weight lignin

Kadam

Chin

Brown

2009

Env Prog and Sustain Energy

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A continuous biomass fractionation process for producing ethanol and low-molecular-weight lignin was developed, and its economic feasibility was evaluated. The two-stage process fractionates biomass into three streams: a solid cellulose stream and two liquid streams containing mostly hemicellulosic sugars and lignin, respectively. Process optimization was conducted using corn stover as feedstock in a continuous pilot-scale unit, with the goals of efficient hemicellulose and lignin hydrolysis for the countercurrent first and cocurrent second stage, respectively. Countercurrent prehydrolysis in an extruder is a novel feature of the process. Autohydrolysis at 2108C followed by NaOH (0.06 g/g biomass) catalyzed delignification at 2208C was determined to be optimal. Economic feasibility of the process for ethanol production was compared to that of the National Renewable Energy Laboratory (NREL; Golden, CO) process. Major differences between the two scenarios are that the PureVision process generates lignin as a sellable output but needs to replace the lost fuel value of the lignin with additional stover. The minimum ethanol selling price, calculated following the NREL protocol, is projected to be lower for the PureVision process ($0.94/gal) than that for the NREL process ($1.07/gal)-the differential depending on lignin selling price-indicating a process with commercial potential.

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“…Esteghlalian et al [31] reported similar kinetic behavior, although other investigators have reported that temperature has little effect on maximum xylose yields [32,33].…”

Section: Acid-catalyzed Prehydrolysis/pretreatmentmentioning

confidence: 84%

Continuous biomass fractionation process for producing ethanol and low‐molecular‐weight lignin

Kadam

Chin

Brown

2009

Env Prog and Sustain Energy

View full text Add to dashboard Cite

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“…Physical treatments such as heating are extensively reported and have been shown to be more effective for disruption of cellulose structure, thereby enhancing the porosity of biomass residues and their accessibility to microorganisms during fermentation. however, this type of pretreatment is energy-consuming and does not remove the lignin content which withstands the enzymatic degradation (14,87). Most of the chemical pretreatments that have been assessed to date (typically acid and alkali based methods) have the primary goal of enhancing the accessibility of biohydrogen-producing bacteria to cellulose by solubilizing the hemicellulose and lignin, and to a lesser degree decreasing the degree of polymerization and crystallinity of the cellulosic component and thus allowing biohydrogen-producing bacteria to have access to soluble sugars (42).…”

Section: Applications Of Response Surface Methodology For Determinatimentioning

confidence: 99%

Fermentative Biohydrogen Modelling and Optimization Research in Light of Miniaturized Parallel Bioreactors

Sekoai

Kana

2013

Biotechnology & Biotechnological Equipment

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“…Lignin acts as a physical barrier, preventing the digestible parts of the substrate from being hydrolysed, and binds non-productively to the cellulolytic enzymes [8]. The presence of hemicellulose reduces the mean pore size of the substrate and therefore reduces the accessibility of cellulose to hydrolytic enzymes.…”

Section: Lignin and Hemicellulose Contentsmentioning

confidence: 99%

Biological Pretreatment of Lignocellulosic Substrates for Enhanced Delignification and Enzymatic Digestibility

2011

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Sheer enormity of lignocellulosics makes them potential feedstock for biofuel production but, their conversion into fermentable sugars is a major hurdle. They have to be pretreated physically, chemically, or biologically to be used by fermenting organisms for production of ethanol. Each lignocellulosic substrate is a complex mix of cellulose, hemicellulose and lignin, bound in a matrix. While cellulose and hemicellulose yield fermentable sugars, lignin is the most recalcitrant polymer, consisting of phenyl-propanoid units. Many microorganisms in nature are able to attack and degrade lignin, thus making access to cellulose easy. Such organisms are abundantly found in forest leaf litter/composts and especially include the wood rotting fungi, actinomycetes and bacteria. These microorganisms possess enzyme systems to attack, depolymerize and degrade the polymers in lignocellulosic substrates. Current pretreatment research is targeted towards developing processes which are mild, economical and environment friendly facilitating subsequent saccharification of cellulose and its fermentation to ethanol. Besides being the critical step, pretreatment is also cost intensive. Biological treatments with white rot fungi and Streptomyces have been studied for delignification of pulp, increasing digestibility of lignocellulosics for animal feed and for bioremediation of paper mill effluents. Such lignocellulolytic organisms can prove extremely useful in production of bioethanol when used for removal of lignin from lignocellulosic substrate and also for cellulase production. Our studies on treatment of hardwood and softwood residues with Streptomyces griseus isolated from leaf litter showed that it enhanced the mild alkaline solubilisation of lignins and also produced high levels of the cellulase complex when growing on wood substrates. Lignin loss (Klason lignin) observed was 10.5 and 23.5% in case of soft wood and hard wood, respectively. Thus, biological pretreatment process for lignocellulosic substrate using lignolytic organisms such as actinomycetes and white rot fungi can be developed for facilitating efficient enzymatic digestibility of cellulose.

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An Overview of Factors Influencing the Enzymatic Hydrolysis of Lignocellulosic Feedstocks

Cited by 38 publications

References 0 publications

Continuous biomass fractionation process for producing ethanol and low‐molecular‐weight lignin

Continuous biomass fractionation process for producing ethanol and low‐molecular‐weight lignin

Fermentative Biohydrogen Modelling and Optimization Research in Light of Miniaturized Parallel Bioreactors

Biological Pretreatment of Lignocellulosic Substrates for Enhanced Delignification and Enzymatic Digestibility

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