Lignin contributions to the nanoscale porosity of raw and treated lignocelluloses as observed by calorimetric thermoporometry

Driemeier, Carlos; Oliveira, Marcelo M.; Curvelo, A. A. S.

doi:10.1016/j.indcrop.2015.11.084

Cited by 22 publications

(14 citation statements)

References 22 publications

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“…This can also lead to an enhancement in the accessibility to the lignin and so to an increase in its unproductive binding to enzymes [ 62 , 63 ]. The increase in porosity and lignin removal are likely to be intertwined as lignin has a well-known pore-filler role [ 17 ].…”

Section: Resultsmentioning

confidence: 99%

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Multimodal analysis of pretreated biomass species highlights generic markers of lignocellulose recalcitrance

Herbaut

Zoghlami

Habrant

et al. 2018

Biotechnol Biofuels

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BackgroundBiomass recalcitrance to enzymatic hydrolysis has been assigned to several structural and chemical factors. However, their relative importance remains challenging to evaluate. Three representative biomass species (wheat straw, poplar and miscanthus) were submitted to four standard pretreatments (dilute acid, hot water, ionic liquid and sodium chlorite) in order to generate a set of contrasted samples. A large array of techniques, including wet chemistry analysis, porosity measurements using NMR spectroscopy, electron and fluorescence microscopy, were used in order to determine possible generic factors of biomass recalcitrance.ResultsThe pretreatment conditions selected allowed obtaining samples displaying different susceptibility to enzymatic hydrolysis (from 3 up to 98% of the initial glucose content released after 96 h of saccharification). Generic correlation coefficients were calculated between the measured chemical and structural features and the final saccharification rates. Increases in porosity displayed overall strong positive correlations with saccharification efficiency, but different porosity ranges were concerned depending on the considered biomass. Lignin-related factors displayed highly negative coefficients for all biomasses. Lignin content, which is likely involved in the correlations observed for porosity, was less detrimental to enzymatic hydrolysis than lignin composition. Lignin influence was highlighted by the strong negative correlation with fluorescence intensity which mainly originates from monolignols in mature tissues.ConclusionsOur results provide a better understanding of the factors responsible for biomass recalcitrance that can reasonably be considered as generic. The correlations with specific porosity ranges are biomass species-dependent, meaning that enzymes cocktails with fitted enzyme size are likely to be needed to optimise saccharification depending on the biomass origin. Lignin composition, which probably influences its structure, is the most important parameter to overcome to enhance enzymes access to the polysaccharides. Accordingly, fluorescence intensity was found to be a rapid and simple method to assess recalcitrance after pretreatment.Electronic supplementary materialThe online version of this article (10.1186/s13068-018-1053-8) contains supplementary material, which is available to authorised users.

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Section: Resultsmentioning

confidence: 99%

“…Biomass porosity is partially attributed to its lignin content [ 17 ]. Although lignin is recognised as one of the main factors hindering biomass conversion, understanding the influence of its composition and structure is still challenging.…”

Section: Introductionmentioning

confidence: 99%

Multimodal analysis of pretreated biomass species highlights generic markers of lignocellulose recalcitrance

Herbaut

Zoghlami

Habrant

et al. 2018

Biotechnol Biofuels

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“…It is worthwhile to analyze FBW profiles looking separately into different length scales. Following a previous study [ 19 ], we separately analyzed FBW < 4 nm and the 10–200-nm range (Fig. 3 c), the latter expressed as pore area in units of m 2 /g.…”

Section: Resultsmentioning

confidence: 99%

“…The main output from the technique is the FBW profile, given as cumulative distribution as a function of pore diameter in the range of 1–200 nm. Thermoporometry analysis was executed using a DSC TA Q200 with an auto sampler and RCS90 cooling unit, according to the procedure described previously [ 33 ] and recently updated [ 19 ].…”

Section: Methodsmentioning

confidence: 99%

Toward an understanding of the increase in enzymatic hydrolysis by mechanical refining

Assis

Huang

Driemeier

et al. 2018

Biotechnol Biofuels

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BackgroundMechanical refining is a low-capital and well-established technology used in pulp and paper industry to improve fiber bonding for product strength. Refining can also be applied in a biorefinery context to overcome the recalcitrance of pretreated biomass by opening up the biomass structure and modifying substrate properties (e.g., morphology, particle size, porosity, crystallinity), which increases enzyme accessibility to substrate and improves carbohydrate conversion. Although several characterization methods have been used to identify the changes in substrate properties, there is no systematic approach to evaluate the extent of fiber cell wall disruption and what physical properties can explain the improvement in enzymatic digestibility when pretreated lignocellulosic biomass is mechanically refined. This is because the fiber cell wall is complex across multiple scales, including the molecular scale, nano- and meso-scale (microfibril), and microscale (tissue level). A combination of advanced characterization tools is used in this study to better understand the effect of mechanical refining on the meso-scale microfibril assembly and the relationship between those meso-scale modifications and enzymatic hydrolysis.ResultsEnzymatic conversion of autohydrolysis sugarcane bagasse was improved from 69.6 to 77.2% (11% relative increase) after applying mechanical refining and an increase in enzymatic digestibility is observed with an increase in refining intensity. Based on a combination of advanced characterizations employed in this study, it was found that the refining action caused fiber size reduction, internal delamination, and increase in pores and swellability.ConclusionsA higher level of delamination and higher increase in porosity, analyzed by TEM and DSC, were clearly demonstrated, which explain the faster digestibility rate during the first 72 h of enzymatic hydrolysis for disc-refined samples when compared to the PFI-refined samples. In addition, an increased inter-fibrillar distance between cellulose microfibrils at the nano–meso-scale was also revealed by SFG analysis, while no evidence was found for a change in crystalline structure by XRD and solid-state NMR analysis.

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“…12,21,22 It has been shown that such aggregates contribute to a characteristic thermoporometric Figure 5c), which was attributed to water pockets associated with surface irregularities of the lignin aggregates. 23 This thermoporometric signature is absent after alkaline reactions ( Figure 5a,b), indicating absence of lignin aggregates in the alkalitreated biomass.…”

Section: ■ Resultsmentioning

confidence: 94%

Produção de etanol celulósico por >i<Spathaspora passalidarum>/i< a partir do bagaço de cana-de-açúcar: estratégia para melhorar fermentabilidade e estudo do perfil metabólico durante fermentação de hidrolisado hemicelulósico

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Lignin contributions to the nanoscale porosity of raw and treated lignocelluloses as observed by calorimetric thermoporometry

Cited by 22 publications

References 22 publications

Multimodal analysis of pretreated biomass species highlights generic markers of lignocellulose recalcitrance

Multimodal analysis of pretreated biomass species highlights generic markers of lignocellulose recalcitrance

Toward an understanding of the increase in enzymatic hydrolysis by mechanical refining

Produção de etanol celulósico por >i<Spathaspora passalidarum>/i< a partir do bagaço de cana-de-açúcar: estratégia para melhorar fermentabilidade e estudo do perfil metabólico durante fermentação de hidrolisado hemicelulósico

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