Biological Pretreatment of Lignocellulosic Biomass

Vasco‐Correa, Juliana; Ge, Xinna; Li, Y.

doi:10.1016/b978-0-12-802323-5.00024-4

Cited by 43 publications

(29 citation statements)

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“…Fungal pretreatment is generally performed using wood-rotting fungi, such as white-, brown-, or soft-rot fungi, due to their ability to modify the components of the lignocellulosic biomass. Brown-rot fungi mainly degrade cellulose and hemicellulose, with little modification to the lignin, which is detrimental for the production of fermentable sugars [18]. Some soft-rot fungi have shown the ability to degrade lignin, while most of soft-rot fungi can only slightly modify it, while significantly degrading the structural carbohydrates [19].…”

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“…Additionally, fungal pretreatment is effective at larger feedstock particle sizes than most conventional pretreatments [17]. However, fungal pretreatment has some potential disadvantages compared to traditional pretreatments, including long reaction times (several weeks compared to hours), lower sugar yields (maximum sugar yields around 75% vs. >90%), and feedstock sterilization requirements [18].The fungal pretreatment of woody and herbaceous feedstocks has been performed using a variety of white-rot fungal strains. The fungal pretreatment of hardwoods such as poplar, willow, and rubberwood has resulted in 18-30% lignin degradation and a glucose yield of 17-55%, using strains such as Ceriporiopsis subvermispora, Echinodontium taxoddi, Trametes orientalis, and Trametes velutina [21][22][23][24][25][26].…”

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Techno-Economic Bottlenecks of the Fungal Pretreatment of Lignocellulosic Biomass

Vasco‐Correa

Shah

2019

Fermentation

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Fungal pretreatment is a biological process that uses rotting fungi to reduce the recalcitrance and enhance the enzymatic digestibility of lignocellulosic feedstocks at low temperature, without added chemicals and wastewater generation. Thus, it has been presumed to be low cost. However, fungal pretreatment requires longer incubation times and generates lower yields than traditional pretreatments. Thus, this study assesses the techno-economic feasibility of a fungal pretreatment facility for the production of fermentable sugars for a 75,700 m 3 (20 million gallons) per year cellulosic bioethanol plant. Four feedstocks were evaluated: perennial grasses, corn stover, agricultural residues other than corn stover, and hardwood. The lowest estimated sugars production cost ($1.6/kg) was obtained from corn stover, and was 4-15 times as much as previous estimates for conventional pretreatment technologies. The facility-related cost was the major contributor (46-51%) to the sugar production cost, mainly because of the requirement of large equipment in high quantities, due to process bottlenecks such as low sugar yields, low feedstock bulk density, long fungal pretreatment times, and sterilization requirements. At the current state of the technology, fungal pretreatment at biorefinery scale does not appear to be economically feasible, and considerable process improvements are still required to achieve product cost targets.Fermentation 2019, 5, 30 2 of 23 of water [5]. Additionally, most commercially available pretreatments, such as dilute acid and liquid hot water pretreatment, require an additional detoxification step, because their severe conditions promote the generation of compounds derived from lignocellulose, such as furans, weak acids and aromatic compounds, which could inhibit fermentative microorganisms, such as yeast and bacteria [6].A series of alternative methods have been proposed to reduce the severity of the conditions required for biomass fractionation and pretreatment. Use of extrusion, microwaves, ultrasound, or pulse electric field has shown to improve the biomass pretreatment process and allowed for the use of milder pretreatment conditions [7]. Biomass pretreatment with aqueous organic solvents (organosolv) [8,9], ozone (ozonolysis) [10], ionic liquids [11,12], or deep eutectic solvents [13] has shown promising results in biomass fractionation [14,15]. However, concerns about the costs, handling, and recovery of the chemicals present limitations in their large-scale applicability [14,16].Fungal pretreatment is as an alternative to conventional pretreatments that is performed at 25-30 • C, atmospheric pressure, in solid-state with low water use, and without added chemicals that can be corrosive and would need disposal or recovery [17]. Fungal pretreatment is generally performed using wood-rotting fungi, such as white-, brown-, or soft-rot fungi, due to their ability to modify the components of the lignocellulosic biomass. Brown-rot fungi mainly degrade cellulose and hemicellulose, with little modificati...

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Techno-Economic Bottlenecks of the Fungal Pretreatment of Lignocellulosic Biomass

Vasco‐Correa

Shah

2019

Fermentation

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“…Advantages include low energy consumption and capital costs. However, due to the slow rate, biological pretreatment is relevant only if combined with other methods or with storage prior to other forms of pretreatment [36].…”

Section: Pretreatment For Enzymatic Saccharificationmentioning

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Analytical Enzymatic Saccharification of Lignocellulosic Biomass for Conversion to Biofuels and Bio-Based Chemicals

2018

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Lignocellulosic feedstocks are an important resource for biorefining of renewables to bio-based fuels, chemicals, and materials. Relevant feedstocks include energy crops, residues from agriculture and forestry, and agro-industrial and forest-industrial residues. The feedstocks differ with respect to their recalcitrance to bioconversion through pretreatment and enzymatic saccharification, which will produce sugars that can be further converted to advanced biofuels and other products through microbial fermentation processes. In analytical enzymatic saccharification, the susceptibility of lignocellulosic samples to pretreatment and enzymatic saccharification is assessed in analytical scale using high-throughput or semi-automated techniques. This type of analysis is particularly relevant for screening of large collections of natural or transgenic varieties of plants that are dedicated to production of biofuels or other bio-based chemicals. In combination with studies of plant physiology and cell wall chemistry, analytical enzymatic saccharification can provide information about the fundamental reasons behind lignocellulose recalcitrance as well as about the potential of collections of plants or different fractions of plants for industrial biorefining. This review is focused on techniques used by researchers for screening the susceptibility of plants to pretreatment and enzymatic saccharification, and advantages and disadvantages that are associated with different approaches.

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“…Plants have evolved to make lignocellulose that is difficult to degrade, so biomass deconstruction requires expensive and energy-intensive methods. Deconstruction can be accomplished mechanically [7,8], chemically [9], physiochemically [10], and biologically [11]. Consolidated bioprocessing can simplify this process, since a single microbe is responsible for both deconstruction and conversion [12].…”

Section: Introductionmentioning

confidence: 99%

Modular Engineering of Biomass Degradation Pathways

Chaves

Presley

2019

Processes

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Production of fuels and chemicals from renewable lignocellulosic feedstocks is a promising alternative to petroleum-derived compounds. Due to the complexity of lignocellulosic feedstocks, microbial conversion of all potential substrates will require substantial metabolic engineering. Non-model microbes offer desirable physiological traits, but also increase the difficulty of heterologous pathway engineering and optimization. The development of modular design principles that allow metabolic pathways to be used in a variety of novel microbes with minimal strain-specific optimization will enable the rapid construction of microbes for commercial production of biofuels and bioproducts. In this review, we discuss variability of lignocellulosic feedstocks, pathways for catabolism of lignocellulose-derived compounds, challenges to heterologous engineering of catabolic pathways, and opportunities to apply modular pathway design. Implementation of these approaches will simplify the process of modifying non-model microbes to convert diverse lignocellulosic feedstocks.

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Biological Pretreatment of Lignocellulosic Biomass

Cited by 43 publications

References 81 publications

Techno-Economic Bottlenecks of the Fungal Pretreatment of Lignocellulosic Biomass

Techno-Economic Bottlenecks of the Fungal Pretreatment of Lignocellulosic Biomass

Analytical Enzymatic Saccharification of Lignocellulosic Biomass for Conversion to Biofuels and Bio-Based Chemicals

Modular Engineering of Biomass Degradation Pathways

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