Alkaline degradation of model compounds related to (4-O-methyl-d-glucurono)-d-xylan

Simkovic, I; Ebringerová, Anna; Hirsch, Ján; Königstein, Jozef

doi:10.1016/s0008-6215(00)90293-3

Cited by 8 publications

(2 citation statements)

References 9 publications

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“…In alkaline pulping, 4-O-methylglucuronic acid (MeGlcA) side-groups attached to the xylan backbone are degraded by about 75-90% (Buchert et al, 1995(Buchert et al, , 1997a. The residual MeGlcA are partially converted to unsaturated 4-deoxy-b-L-threo-hex-4-enopyranosyluronic acid groups (hexenuronic acid or HexA) by b-elimination of methanol directly or via the intermediate product 4-O-methyliduronic acid (Clayton, 1963;Johansson and Samuelson, 1977;Simkovic et al, 1986). HexA was identified as a major uronic acid (UA) substituent both of the industrial kraft pulp and of some unconventional alkali-based organosolv pulps, accounting for 83-88% of total UA (Buchert et al, 1997a;Shatalov and Pereira, 2004).…”

Section: Introductionmentioning

confidence: 99%

Impact of hexenuronic acids on xylanase-aided bio-bleaching of chemical pulps

Shatalov¹,

Pereira²

2009

Bioresource Technology

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Hexenuronic acids (HexA) of hemicellulosic heteroxylan were shown to play important role in brightness development of chemical pulps during xylanase-aided bio-bleaching. Industrial wood (eucalypt) kraft pulp and a few non-wood (giant reed) organosolv pulps were pre-treated with commercial xylanase preparations (endo-1,4-beta-xylanase activity; EC 3.2.1.8) and bleached by simplified bleaching sequence. The HexA performance was examined and compared with control (enzyme-free) samples. The xylanase-assisted direct brightening effect, noted immediately after an enzymatic stage, was proved to be caused by exclusive HexA removal with solubilized HexA-carrying xylooligosaccharide fractions. Aldohexa- and aldopentahexenuronic acids (Xyl(5)-HexA and Xyl(4)-HexA) were found as predominant oligosaccharides, accounting for up to 65% of total acidic oligomers in enzymatic hydrolyzates. A strong positive correlation (R(2)=0.91) was established between further brightness improvement of xylanase-treated pulps during subsequent chemical bleaching (bleach boosting) and the content of HexA. This underlined the role of HexA as one of the key factors in definition of final brightness of bio-bleached pulps, determining to a large extent the bleaching efficiency of xylanase application as a whole.

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Section: Introductionmentioning

confidence: 99%

Impact of hexenuronic acids on xylanase-aided bio-bleaching of chemical pulps

Shatalov¹,

Pereira²

2009

Bioresource Technology

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“…In general, there are a few caveats of the proposed method and caution is pertinent as D Lignin (%) delineates the overall decrease in lignin content where the intensity drop could stem not only from the breakdown of the polymeric backbone of lignin but also from the chromophore groups. We note that one of the chromophore groups which could hinder the fluorometric observation is 4-deoxy-4-hexenuronic acid (HexA), usually formed from the partial conversion of 4-O-methyl glucuronic acid groups in xylans during Kraft pulping, often found in with mid-range Kappa number ( K > 25, lignin content > 5 wt.%) 45 – 47 . We anticipate that in Ligno-Pulp with low-range K (value of 23.4), HexA content would be a minor component and since one of the cement hydration products, i.e., calcium hydroxide (CH) forms a high-alkaline ([OH] − : 700 mmol/L versus 275 mmol/L in Kraft process) buffer solution 48 — CH will certainly attack any labile unsaturated unit in the residual lignin structure of Ligno-Pulp, which is detrimental to the stability of natural fibre in fibre cement 49 .…”

Section: Resultsmentioning

confidence: 99%

Unraveling lignin degradation in fibre cement via multidimensional fluorometry

Hoque

Kamal

Raghunath

et al. 2023

Sci Rep

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Pulp fibre reinforced cement (fibre cement) has the potential to become a forerunner in mitigating the carbon dioxide (CO2) footprint of non-structural materials for residential and commercial structures. However, one of the significant bottlenecks in fibre cement is its poor chemical stability in the alkaline cement matrix. To date, probing the health of pulp fibre in cement is lengthy and laborious, requiring mechanical and chemical separations. In this study, we have demonstrated that it is possible to understand the chemical interactions at the fibre-cement interfaces by tracking lignin in a solid state without using any additional chemicals. For the first time, multidimensional fluorometry is employed for the rapid assessment of the structural change (degradation) of lignin in fibre cement as an indicator of pulp fibre health; providing an excellent platform for the germination of resilient fibre cement with high content of natural lignocellulosic fibre.

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