Features of Promising Technologies for Pretreatment of Lignocellulosic Biomass

Laboratory of Renewable Resources Engineering, Department of Agricultural and Biological Engineering, Purdue University, Potter Engineering Center, 500 Central Drive, West Lafayette, IN 47907-2022, USA.
Bioresource Technology (Impact Factor: 4.49). 05/2005; 96(6):673-86. DOI: 10.1016/j.biortech.2004.06.025
Source: PubMed


Cellulosic plant material represents an as-of-yet untapped source of fermentable sugars for significant industrial use. Many physio-chemical structural and compositional factors hinder the enzymatic digestibility of cellulose present in lignocellulosic biomass. The goal of any pretreatment technology is to alter or remove structural and compositional impediments to hydrolysis in order to improve the rate of enzyme hydrolysis and increase yields of fermentable sugars from cellulose or hemicellulose. These methods cause physical and/or chemical changes in the plant biomass in order to achieve this result. Experimental investigation of physical changes and chemical reactions that occur during pretreatment is required for the development of effective and mechanistic models that can be used for the rational design of pretreatment processes. Furthermore, pretreatment processing conditions must be tailored to the specific chemical and structural composition of the various, and variable, sources of lignocellulosic biomass. This paper reviews process parameters and their fundamental modes of action for promising pretreatment methods.

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Available from: Bruce Edwin Dale, Sep 29, 2015
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    • "These parameters can be used to benchmark a conceptual process design. Process economic analysis also enables estimation of an absolute production cost for ethanol or other potential products necessary for comparing biorefinery-based costs to existing processes [3]. The combination of experimental data and economic modelling results in a matrix that matches feedstocks with different pretreatment options, as well as for comparing the impact of each stage of processes. "
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    ABSTRACT: Several strategies based on a two steps organosolv pretreatment followed by enzymatic hydrolysis of sugarcane bagasse (SCB) were evaluated with the objective of selecting operational conditions suitable to promote an efficient and low cost production of ethanol. Initially, the influence of six variables used for the organosolv pretreatment was studied. The variables included the time of the first organosolv pretreatment step, the use of 45% ethanol as pulping solution, solid-to-liquid ratio of the ethanol solution used during the first pretreatment step, time of second organosolv pretreatment, concentration of ethanol and concentration of NaOH solution used in the second pretreatment step. Further assays of enzymatic hydrolysis were carried out to promote additional reduction in the costs of the process and improve the results of cellulose conversion to glucose. Eliminating the milling step of the pretreated SCB, using a commercial tensoactive (composed of esters and several surfactants), and recycling 50% of the slurry obtained during the second step of organosolv pretreatment as reaction medium proved to be feasible for use during the enzymatic hydrolysis. Fermentation of the glucose medium produced under the selected pretreatment conditions to ethanol by Saccharomyces cerevisiae occurred with 81% efficiency and a cost of 102.88 $/hL of ethanol.
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    • "Table 1, in NaOH hydrolysis, the alkali hydrolysed the end groups of polysaccharides and thus promoted degradation and decomposition. This is because it leads to delignification, disruption of structural linkages, decrystallization of cellulose, and depolymerization of the carbohydrates (Esposito et al. 1993; Mosier et al. 2005). Sodium hydroxide acts as a nucleophile during lignin degradation, which fragments and dissolves lignin. "
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    ABSTRACT: This study compares the efficacy of a soaking pretreatment with an alkaline solution for banana pseudostem prior to enzymatic hydrolysis. Banana pseudostem was pretreated by soaking in sodium hydroxide solutions at various concentrations and durations. The pretreatment more than doubled delignification but retained 82.09% of the holocellulose content and 73.74% of the cellulose content. The enzymatic (Trichoderma reesei) digestibility of pretreated banana pseudostem was found to have been enhanced by 44.41% as compared to initial biomass. This was evidenced by higher enzymatic activities (endoglucanase, exoglucanase, and β-glucosidase) on the treated sample. Meanwhile, glucose yield showed a proportional relationship with incubation time and enzyme loading throughout the hydrolysis process.
    Bioresources 11/2015; 10(1):1213-1223. DOI:10.15376/biores.10.1.1213-1223 · 1.43 Impact Factor
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    • "The increased photosynthetic efficiency of elephant grass is attributed to its C4 metabolism (Euclides et al., 2008). Steam explosion is recognised as one of the most effective and widely used pretreatment methods developed to date (Mosier et al., 2005; Ramos, 2003; Ramos et al., 1992, 2000). Steam explosion allows a relatively easy fractionation and recovery in high yields of the three main components of the plant cell wall: cellulose, hemicellulose, and lignin (Brugnago et al., 2011). "
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    ABSTRACT: In this work, steam explosion was used a pretreatment method to improve the conversion of elephant grass (Pennisetum purpureum) to cellulosic ethanol. This way, enzymatic hydrolysis of vaccum-drained and water-washed steam-treated substrates was carried out with Penicillium echinulatum enzymes while Saccharomyces cerevisiae CAT-1 was used for fermentation. After 48h of hydrolysis, the highest yield of reducing sugars was obtained from vaccum-drained steam-treated substrates that were produced after 10min at 200°C (863.42±62.52mg/g). However, the highest glucose yield was derived from water-washed steam-treated substrates that were produced after 10min at 190°C (248.34±6.27mg/g) and 200°C (246.00±9.60mg/g). Nevertheless, the highest ethanol production was obtained from water-washed steam-treated substrates that were produced after 6min at 200°C. These data revealed that water washing is a critical step for ethanol production from steam-treated elephant grass and that pretreatment generates a great deal of water soluble inhibitory compounds for hydrolysis and fermentation, which were partly characterized as part of this study. Copyright © 2015 Elsevier Ltd. All rights reserved.
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