Improving Enzymatic Saccharification and Ethanol Production from Hardwood by Deacetylation and Steam Pretreatment: Insight into Mitigating Lignin Inhibition

Chu, Qiulu; Wang, Rui; Tong, Wenyao; Jin, Yongcan; Hu, Jinguang; Song, Kai

doi:10.1021/acssuschemeng.0c05583

Cited by 41 publications

(14 citation statements)

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“…The negative effects of lignin on enzymatic hydrolysis have been comprehensively reviewed and discussed by many researchers. − , We also confirmed the inhibition of lignin (milled bamboo lignin, MBL) to the enzymatic conversion (EC) of typical microcrystalline cellulose (Avicel) (Figure S3). Based on macroscopic adsorption experiments, numerous studies had found that competitive adsorption of cellulase with lignin was more superior to that with cellulose in a coexisting buffer system, which significantly reduced the amount of effective cellulase molecules in the buffer solution for catalyzing the cellulose hydrolysis and in turn the glucose yield. ,, It is thus speculated that lignin might exhibit a higher adhesion strength with cellulase than that with cellulose …”

Section: Resultssupporting

confidence: 69%

Nanomechanics of Lignin–Cellulase Interactions in Aqueous Solutions

Zheng

Chang

et al. 2021

Biomacromolecules

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Efficient enzymatic hydrolysis of cellulose in lignocellulose to glucose is one of the most critical steps for the production of biofuels. The nonproductive adsorption of lignin to expensive cellulase highly impedes the development of biorefinery. Understanding the lignin–cellulase interaction mechanism serves as a vital basis for reducing such nonproductive adsorption in their practical applications. Yet, limited report is available on the direct characterization of the lignin–cellulase interactions. Herein, for the first time, the nanomechanics of the biomacromolecules including lignin, cellulase, and cellulose were systematically investigated by using a surface force apparatus (SFA) at the nanoscale in aqueous solutions. Interestingly, a cation−π interaction was discovered and demonstrated between lignin and cellulase molecules through SFA measurements with the addition of different cations (Na+, K+, etc.). The complementary adsorption tests and theoretical calculations further confirmed the validity of the force measurement results. This finding further inspired the investigation of the interaction between lignin and other noncatalytic-hydrolysis protein (i.e., soy protein). Soy protein was demonstrated as an effective, biocompatible, and inexpensive lignin-blocker based on the molecular force measurements through the combined effects of electrostatic, cation−π, and hydrophobic interactions, which significantly improved the enzymatic hydrolysis efficiencies of cellulose in pretreated lignocellulosic substrates. Our results offer quantitative information on the fundamental understanding of the lignin–cellulase interaction mechanism. Such unraveled nanomechanics provides new insights into the development of advanced biotechnologies for addressing the nonproductive adsorption of lignin to cellulase, with great implications on improving the economics of lignocellulosic biorefinery.

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Section: Resultssupporting

confidence: 69%

Nanomechanics of Lignin–Cellulase Interactions in Aqueous Solutions

Zheng

Chang

et al. 2021

Biomacromolecules

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“…4 c). In addition, the lignin coverage on fiber surface of EOS + 2N substrate was also quantitatively determined by O/C ratio of XPS analysis [ 45 ], which was even higher than that on EOS substrate surface (Table 4 ). Results confirmed the aggravated exterior lignin coverage caused by 2-naphthol addition in acid EOS treatment, which in turn proved the greater fluidity of the less repolymerized lignin that modified by 2-naphthol.…”

Section: Resultsmentioning

confidence: 99%

“…Enzymatic hydrolysis of the delignified substrate was performed as specified above. The gap between enzymatic hydrolysis of delignified and non-delignified EOS substrates indicated the total lignin inhibition on cellulose hydrolysis, including unproductive binding effect and surface barrier effect [ 45 ].…”

Section: Methodsmentioning

confidence: 99%

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Organosolv pretreatment assisted by carbocation scavenger to mitigate surface barrier effect of lignin for improving biomass saccharification and utilization

Chu

Tong

Chen

et al. 2021

Biotechnol Biofuels

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Background Ethanol organosolv (EOS) pretreatment is one of the most efficient methods for boosting biomass saccharification as it can achieve an efficient fractionation of three major constituents in lignocellulose. However, lignin repolymerization often occurs in acid EOS pretreatment, which impairs subsequent enzymatic hydrolysis. This study investigated acid EOS pretreatment assisted by carbocation scavenger (2-naphthol, 2-naphthol-7-sulfonate, mannitol and syringic acid) to improve biomass fractionation, coproduction of fermentable sugars and lignin adsorbents. In addition, surface barrier effect of lignin on cellulose hydrolysis was isolated from unproductive binding effect of lignin, and the analyses of surface chemistry, surface morphology and surface area were carried out to reveal the lignin inhibition mitigating effect of various additives. Results Four different additives all helped mitigate lignin inhibition on cellulose hydrolysis in particular diminishing surface barrier effect, among which 2-naphthol-7-sulfonate showed the best performance in improving pretreatment efficacy, while mannitol and syringic acid could serve as novel green additives. Through the addition of 2-naphthol-7-sulfonate, selective lignin removal was increased up to 76%, while cellulose hydrolysis yield was improved by 85%. As a result, 35.78 kg cellulose and 16.63 kg hemicellulose from 100 kg poplar could be released and recovered as fermentable sugars, corresponding to a sugar yield of 78%. Moreover, 22.56 kg ethanol organosolv lignin and 17.53 kg enzymatic hydrolysis residue could be recovered as lignin adsorbents for textile dye removal, with the adsorption capacities of 45.87 and 103.09 mg g−1, respectively. Conclusions Results in this work indicated proper additives could give rise to the form of less repolymerized surface lignin, which would decrease the unproductive binding of cellulase enzymes to surface lignin. Besides, the supplementation of additives (NS, MT and SA) resulted in a simultaneously increased surface area and decreased lignin coverage. All these factors contributed to the diminished surface barrier effect of lignin, thereby improving the ease of enzymatic hydrolysis of cellulose. The biorefinery process based on acidic EOS pretreatment assisted by carbocation scavenger was proved to enable the coproduction of fermentable sugars and lignin adsorbents, allowing the holistic utilization of lignocellulosic biomass for a sustainable biorefinery. Graphic abstract

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“…Then, the hydrolysate was transferred to a screw-capped tube and boiled for 5 min to stop the enzymatic reaction. The obtained solution was analyzed for the contents of the released reducing sugars using HPLC and the degree of saccharification (DS) , using eq . DS = c · v · f 1 m · f 2 where c denotes the concentration of sugar in the hydrolysate (mg mL –1 ), v represents the volume of hydrolysate (mL), f 1 indicates the factor (0.90 for glucose and 0.88 for xylose) used to convert polysaccharide to monosaccharide during saccharification, m refers to the initial weight of the dry substrate (mg), and f 2 denotes the factor for the content of carbohydrate in the substrate, which was cellulose and hemicellulose for DS calculations of glucose and xylose (mg mg –1 ), respectively.…”

Section: Methodsmentioning

confidence: 99%

High Production of Cellulase and Xylanase in Solid-State Fermentation by Trichoderma reesei Using Spent Copra and Wheat Bran in Rotary Bioreactor

Chysirichote

Phaiboonsilpa

Laosiripojana

2023

Ind. Eng. Chem. Res.

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The enzyme production for lignocellulose saccharification by solid-state fermentation (SSF) of a food manufacturing byproduct was successfully carried out in a 30 L rotary bioreactor. Defatted spent copra (SC) supplemented with wheat bran (WB) was used as a substrate for the SSF of Trichoderma reesei and aerated at various rates. Regression analysis showed that the carbohydrate/protein (C/P) ratio of the substrate and the supplied aeration rate were the important factors for producing the enzyme cocktail, including cellulases (FPase, CMCase, and cellobiase) and xylanase. The substrate containing SC:WB of 3:2 (or the C/P ratio of 5.4) and the aeration of 1.0 L kg −1 substrate min −1 were found to enhance the production of the enzymes up to 5.68, 8.66, 29.2, and 34.44 U g −1 of dry substrate for FPase, CMCase, cellobiase, and xylanase activities, respectively. This discovery provided a promising environment for other substrates to produce multi-enzymes for lignocellulosic saccharification. Additionally, mathematical models were generated to predict the saccharifying degree of the produced enzyme for lignocellulose saccharification.

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Improving Enzymatic Saccharification and Ethanol Production from Hardwood by Deacetylation and Steam Pretreatment: Insight into Mitigating Lignin Inhibition

Cited by 41 publications

References 59 publications

Nanomechanics of Lignin–Cellulase Interactions in Aqueous Solutions

Nanomechanics of Lignin–Cellulase Interactions in Aqueous Solutions

Organosolv pretreatment assisted by carbocation scavenger to mitigate surface barrier effect of lignin for improving biomass saccharification and utilization

High Production of Cellulase and Xylanase in Solid-State Fermentation by Trichoderma reesei Using Spent Copra and Wheat Bran in Rotary Bioreactor

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