Dilute nitric-acid pretreatment of oat hulls for ethanol production

Скиба, Е. А.; Будаева, В. В.; Baibakova, O. V.; Золотухин, В. Н.; Сакович, Г. В.

doi:10.1016/j.bej.2016.09.003

Cited by 45 publications

(24 citation statements)

References 31 publications

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“…During the dilute acid pretreatment, hemicellulose is hydrolyzed into monomeric sugars, that is, xylose, arabinose, galactose, glucose, and mannose, with alternations in the lignin structure (Agrawal et al, 2015b(Agrawal et al, , 2017aSkiba et al, 2017). This, in turn, increases the pore volume and surface area of the substrate, improving the enzyme accessibility.…”

Section: Pretreatment and Chemical Composition Of Rice Strawmentioning

confidence: 99%

“…The LCCs enhance the integrity and rigidity of the plant cell wall, yielding a complex macromolecular assembly and rendering the recalcitrance for biorefining (Li et al, 2016). Thus, thermochemical pretreatment is essential to improve enzyme accessibility to carbohydrates, embedded within lignin, to produce fermentable sugars efficiently (Adsul et al, 2014;Agrawal et al, 2015a;Gaur et al, 2015;Saini et al, 2015;Antonopoulou et al, 2016;Skiba et al, 2017).…”

Section: Introductionmentioning

confidence: 99%

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Improved Enzymatic Hydrolysis of Pilot Scale Pretreated Rice Straw at High Total Solids Loading

et al. 2018

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Enzymatic hydrolysis at high solids loading has the potential to reduce both capital and operational expenditures. Here, pretreatment of rice straw (PRS) with dilute acid was carried out at a pilot scale (250 kg per day) at 162 • C for 10 min and 0.35% acid concentration, followed by enzymatic hydrolysis at different total solids loadings. It showed that although the total sugar concentration increased from 48 to 132 g/l, glucan conversion reduced by 27% (84-66.2%) with increasing solids from 5 to 20% in batch mode. Therefore, two different fed-batch approaches were evaluated to improve the glucan conversion by the sequential addition of a substrate and/or enzyme. At 20% solid loadings and a 3 filter paper units/g enzyme dosage, the highest glucan conversion obtained was 66% after 30 h of hydrolysis in batch mode. However, in an optimized fed-batch approach, the glucan yield was improved to 70% by simply dividing the substrate feeding into three batches, that is, 50% at 0 h, 25% each after 4 h, and 8 h of hydrolysis reaction. The addition of surfactant (Ecosurf E6) further improved the conversion to 72% after 30 h. The role of critical factors, that is, inhibitors, enzyme-lignin binding, and viscosity, was investigated during the course of hydrolysis in the batch and fed-batch approaches. This study suggests a sustainable approach for improved hydrolysis at high solids loadings by fine-tuning a simple process.

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Section: Pretreatment and Chemical Composition Of Rice Strawmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Improved Enzymatic Hydrolysis of Pilot Scale Pretreated Rice Straw at High Total Solids Loading

et al. 2018

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“…However, when acid concentrations or reaction times were too high, decomposition products of xylose, such as furfural, become inhibitory. Another study reported the effects of pretreatments of oat hulls with a 4% (w/w) nitric acid solution at atmospheric pressure [33]. These studies showed that pretreatments increased cellulose contents by 2 fold, diminished hemicellulose contents by 4.2 times and lignin contents by 1.5 times, and increased ash contents by 1.3 fold.…”

Section: Effects Of Pretreatments On Lignocellulose Contentsmentioning

confidence: 99%

“…Enzymatic hydrolysis of untreated and nitric acid pretreated oat hull feedstock was investigated previously [33]. The lowest concentration of reducing sugars was observed for untreated oat hulls, and after pretreating oat hulls with nitric acid solution and washing until neutral pH was achieved, the concentration of reducing sugars rose by a factor of 4.3.…”

Section: Effects Of Dilute Acid and Alkaline Concentrations On Sacchamentioning

confidence: 99%

Effect of Dilute Acid and Alkaline Pretreatments on Enzymatic Saccharfication of Palm Tree Trunk Waste for Bioethanol Production

Kusmiyati

Anarki

Nugroho

et al. 2019

Bull. Chem. React. Eng. Catal.

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The sugar palm tree (Arenga pinnata) was abundant in Indonesia and has high cellulose contents for bioethanol production. However, the lignin content was the major drawback which could inhibit saccharification enzymes and therefore removing the lignin from the biomass is important. This paper evaluated the effects of pretreatments using nitric acid (HNO3) and ammonium hydroxide (NH4OH) at 2 to 10% (v/v) on reducing sugar and ethanol contents and compared with the effects of steam pre-treatment. The pretreated samples were hydrolyzed using cellulase enzymes at pH 5.0 with a substrate concentration of 10% (w/v) for 24 to 72 h at 50 °C. Subsequent assessments of enzymatic saccharification following pre-treatment with 10% (v/v) HNO3 showed maximum reducing and total sugar contents in palm tree trunk waste of 5.320% and 5.834%, respectively, after 72 h of saccharification. Following pretreatment with 10% (v/v) of NH4OH, the maximum reducing and total sugar contents of palm tree trunk waste were 2.892% and 3.556%, respectively, after 72 h of saccharification. In comparison, steam pretreatments gave maximum reducing sugar and total sugar contents of 1.140% and 1.315% under the same conditions. Simultaneous saccharification and fermentation (SSF) was conducted at 37 °C (pH 4.8) and 100 rpm for 120 h using 10% (v/v) Saccharomyces cerevisiae and cellulase enzyme with a substrate concentration of 10% (w/v). The result showed the highest ethanol content of 2.648% was achieved by using 10% (v/v) HNO3. The use of 10% (v/v) NH4OH gained a yield of 0.869% ethanol while the steam pretreatment could obtained 0.102% ethanol. Copyright © 2019 BCREC Group. All rights reserved

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“…Oat straw and husks were investigated for the production of biogas [10], xylanase [11], xylitol [12], ethanol [12,13], bacterial cellulose [14][15][16], hydrogels [17], and polypropylene composites [18]. The pretreatment strategies to overcome lignocellulosic recalcitrance mostly included dilute-acid pretreatment using sulfuric acid [11,19] and nitric acid [13,[20][21][22][23], which exhibited the highest impact on dissolution of hemicellulose, and dilute-alkali pretreatment using sodium hydroxide [17,24] and ammonium hydroxide [25], which showed the highest impact on delignification. The use of concentrated salts solutions such as sodium benzoate [26] were also investigated for delignification.…”

Section: Introductionmentioning

confidence: 99%

Biorefining Oat Husks into High-Quality Lignin and Enzymatically Digestible Cellulose with Acid-Catalyzed Ethanol Organosolv Pretreatment

2020

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Oat husks are low-value lignocellulosic residues of oat processing that carry an environmental impact. Their polymers (cellulose, hemicellulose, and lignin) can be converted into a wide variety of value-added products; however, efficient pretreatment methods are needed that allow their fine separation for further tailored valorization. This study pioneered the use of milling-free and low acid-catalyzed ethanol organosolv for the delignification of oat husks, allowing their conversion into three high-quality streams, namely, glucan-rich, lignin-rich, and hemicellulosic compound-rich streams. Temperature, retention time, and solid-to-liquid ratio were found to impact the delignification of oat husks when using a one-factor-at-a-time strategy. The ideal conditions that were found (210 °C, 90 min, and solid-to-liquid ratio of 1:2) culminated into glucan and lignin fractions containing 74.5% ± 11.4% glucan and 74.9% ± 7.6% lignin, respectively. These high-purity lignin fractions open the possibility for higher value applications by lignin, potentially impacting the feasibility of second generation biorefineries. The glucan fraction showed 90% digestibility after 48 h of hydrolysis with 10 filter paper units of enzyme cocktail per gram of glucan. Considering the absence of size reduction and high solid loading, together with the quality of the obtained streams, organosolv pretreatment could be a potential strategy for the valorization of oat lignocellulosic residues.

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Dilute nitric-acid pretreatment of oat hulls for ethanol production

Cited by 45 publications

References 31 publications

Improved Enzymatic Hydrolysis of Pilot Scale Pretreated Rice Straw at High Total Solids Loading

Improved Enzymatic Hydrolysis of Pilot Scale Pretreated Rice Straw at High Total Solids Loading

Effect of Dilute Acid and Alkaline Pretreatments on Enzymatic Saccharfication of Palm Tree Trunk Waste for Bioethanol Production

Biorefining Oat Husks into High-Quality Lignin and Enzymatically Digestible Cellulose with Acid-Catalyzed Ethanol Organosolv Pretreatment

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