Impact of hydrothermal pre-treatment to chemical composition, enzymatic digestibility and spatial distribution of cell wall polymers

Holopainen-Mantila, Ulla; Marjamaa, Kaisa; Merali, Zara; Käsper, Andres; Bot, Peter de; Jääskeläinen, Anna Stiina; Waldron, Keith W.; Kruus, Kristiina; Tamminen, Tarja

doi:10.1016/j.biortech.2013.03.152

Cited by 50 publications

(20 citation statements)

References 31 publications

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“…Fibrous components can be mostly found in the three aleurone layers of the barley grain and mainly consist of cellulose, arabinoxylan and mixed-linked β-glucan [50]. According to previous studies, the arabinoxylan fraction may be more susceptible to low pH and heat than the cellulose and β-glucan fractions [16], [51], [52]. The β-glucan fraction in barley may even be stabilized by LA and heat treatment [16].…”

Section: Discussionmentioning

confidence: 99%

Lactic Acid and Thermal Treatments Trigger the Hydrolysis of Myo-Inositol Hexakisphosphate and Modify the Abundance of Lower Myo-Inositol Phosphates in Barley (Hordeum vulgare L.)

et al. 2014

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Barley is an important source of dietary minerals, but it also contains myo-inositol hexakisphosphate (InsP6) that lowers their absorption. This study evaluated the effects of increasing concentrations (0.5, 1, and 5%, vol/vol) of lactic acid (LA), without or with an additional thermal treatment at 55°C (LA-H), on InsP6 hydrolysis, formation of lower phosphorylated myo-inositol phosphates, and changes in chemical composition of barley grain. Increasing LA concentrations and thermal treatment linearly reduced (P<0.001) InsP6-phosphate (InsP6-P) by 0.5 to 1 g compared to the native barley. In particular, treating barley with 5% LA-H was the most efficient treatment to reduce the concentrations of InsP6-P, and stimulate the formation of lower phosphorylated myo-inositol phosphates such as myo-inositol tetraphosphate (InsP4) and myo-inositol pentaphosphates (InsP5). Also, LA and thermal treatment changed the abundance of InsP4 and InsP5 isomers with Ins(1,2,5,6)P4 and Ins(1,2,3,4,5)P5 as the dominating isomers with 5% LA, 1% LA-H and 5% LA-H treatment of barley, resembling to profiles found when microbial 6-phytase is applied. Treating barley with LA at room temperature (22°C) increased the concentration of resistant starch and dietary fiber but lowered those of total starch and crude ash. Interestingly, total phosphorus (P) was only reduced (P<0.05) in barley treated with LA-H but not after processing of barley with LA at room temperature. In conclusion, LA and LA-H treatment may be effective processing techniques to reduce InsP6 in cereals used in animal feeding with the highest degradation of InsP6 at 5% LA-H. Further in vivo studies are warranted to determine the actual intestinal P availability and to assess the impact of changes in nutrient composition of LA treated barley on animal performance.

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Section: Discussionmentioning

confidence: 99%

Lactic Acid and Thermal Treatments Trigger the Hydrolysis of Myo-Inositol Hexakisphosphate and Modify the Abundance of Lower Myo-Inositol Phosphates in Barley (Hordeum vulgare L.)

et al. 2014

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“…Despite the efforts to explore the mechanism of xylan removal during HTP on a molecular scale, few studies involved the dynamic changes of the ultra-structural localization of xylan in the cell wall during the HTP. Previous studies using immunolabeling techniques demonstrated the sequence of structural changes (DeMartini et al 2011) and xylan reorientation (Holopainen-Mantila et al 2013) that occur in plant cell walls during pretreatment-induced deconstruction. Brunecky et al (2009) showed that xylan accumulated around the cell lumen and middle lamella after dilute acid treatment.…”

Section: Introductionmentioning

confidence: 98%

“…Poplar wood is mainly composed of three component biopolymers: cellulose (42-49 % on a dry weight basis), a linear polymer of b-1,4-linked glucose chains assembled into partially crystalline structures; hemicellulose (16-23 %), heterogeneous branched polymers of pentose and hexose sugars; and lignin (21-29 %), which is composed of extensively cross-linked methoxysubstituted phenyl propane units (Sannigrahi et al 2010;Holopainen-Mantila et al 2013).…”

Section: Introductionmentioning

confidence: 99%

The mechanism of xylans removal during hydrothermal pretreatment of poplar fibers investigated by immunogold labeling

Chen

et al. 2015

Planta

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Hydrothermal pretreatment initially removed the lignin-free xylan from the middle layer of secondary wall, followed by the lignin-bound xylan, but the cellulose-bound xylan was seldom removed by this pretreatment. An in-depth understanding of the mechanism of xylan removal during hydrothermal pretreatment (HTP) of wood is critical for cost-effective conversion of lignocellulosic biomass to biofuels. Several studies demonstrated the kinetics and mechanism of xylan removal during HTP on molecular scale, but the dissolution mechanism of xylan during HTP remains unclear at ultra-structural level. Our study investigated changes in the micro-distribution of xylan in poplar fiber cell walls during HTP by transmission electron microscopy (TEM) in combination with immunogold labeling. The study revealed that HTP caused greater decline in the density of xylan labeling in the S2 layer of fiber wall than in the S1 layer. There was a greater loss in the density of xylan labeling during HTP in the delignified and enzymatically treated fibers compared to untreated fibers. We propose that in the initial stages of HTP lignin-free xylan in the S2 layer was more readily hydrolyzed than in the S1 layer by hydronium ions. With increasing pretreatment time, the xylan covalently bound to lignin was also removed from the S2 layer due to the dissolution of lignin. The xylan tightly bound to cellulose was seldom removed during HTP, but was hydrolyzed in subsequent enzymatic treatment. This TEM-immunolabeling investigation reveals the manner in which different xylan fractions are removed from fiber cell wall during HTP, and we expect the information to be helpful in developing processes tailored for more effective conversion of cellulosic biomass into fermentable sugars.

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“…Once the pretreatment reaction temperature exceeds the critical glass transition temperature of lignin, such aggregates begin to form. The hydrostatic pressures within cell wall layers then force a fraction of these lignin aggregates to the outer face of biomass which in turn contact with the pretreatment bulk solvent and deposit back onto cell wall surfaces [63,108]. Using confocal and fluorescence lifetime imaging microscopy, Coletta et al [112] observed that DAP resulted in a disorder in the arrangement of lignin and its accumulation in the external border of cell walls.…”

Section: Lignin Relocation and Redistributionmentioning

confidence: 97%

Lignin Structural Alterations in Thermochemical Pretreatments with Limited Delignification

Huang

et al. 2015

Bioenerg. Res.

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Lignocellulosic biomass has a complex and rigid cell wall structure that makes biomass recalcitrant to biological and chemical degradation. Among the three major structural biopolymers (i.e., cellulose, hemicellulose, and lignin) in plant cell walls, lignin is considered the most recalcitrant component and generally plays a negative role in the biochemical conversion of biomass to biofuels. The conversion of biomass to biofuels through a biochemical platform usually requires a pretreatment stage to reduce the recalcitrance. Pretreatment renders compositional and structural changes of biomass with these changes ultimately governing the efficiency of the subsequent enzymatic hydrolysis. Dilute acid, hot water, steam explosion, and ammonia fiber expansion pretreatments are among the leading thermochemical pretreatments with a limited delignification that can reduce biomass recalcitrance. Practical applications of these pretreatment are rapidly developing as illustrated by recent commercial scale cellulosic ethanol plants. While these thermochemical pretreatments generally lead to only a limited delignification and no significant change of lignin content in the pretreated biomass, the lignin transformations that occur during these pretreatments and the roles they play in recalcitrance reduction are important research aspects. This review highlights recent advances in our understanding of lignin alterations during these limited delignification thermochemical pretreatments, with emphasis on lignin chemical structures, molecular weights, and redistributions in the pretreated biomass.

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Impact of hydrothermal pre-treatment to chemical composition, enzymatic digestibility and spatial distribution of cell wall polymers

Cited by 50 publications

References 31 publications

Lactic Acid and Thermal Treatments Trigger the Hydrolysis of Myo-Inositol Hexakisphosphate and Modify the Abundance of Lower Myo-Inositol Phosphates in Barley (Hordeum vulgare L.)

Lactic Acid and Thermal Treatments Trigger the Hydrolysis of Myo-Inositol Hexakisphosphate and Modify the Abundance of Lower Myo-Inositol Phosphates in Barley (Hordeum vulgare L.)

The mechanism of xylans removal during hydrothermal pretreatment of poplar fibers investigated by immunogold labeling

Lignin Structural Alterations in Thermochemical Pretreatments with Limited Delignification

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