Characterization of unbleached kraft pulps by enzymatic treatment, potentiometric titration and polyelectrolyte adsorption

Janne Laine, Johanna Buchert, Liisa Viikari, Per Stenius

    Research output: Contribution to journalArticleScientificpeer-review

    104 Citations (Scopus)

    Abstract

    The surface properties of unbleached softwood (Pinus sylvestris) and hardwood (Betula verrucosa) kraft pulps were modified by treating the fibre surfaces with specific xylanase and mannanase (Trichoderma reesei). The amounts and accessibilities of surface carboxyl groups in untreated and enzyme-treated fibres were analyzed using adsorption of cationic polyelectrolytes and high precision potentiometric titration. According to the potentiometric titration both softwood and hardwood pulps contained two types of acidic groups, one with pK(1) approximate to 3.3 (uronic acid in xylan) and one with pK(2) approximate to 5.5 (probably carboxylic group in lignin), The relative amount of the weaker acid in softwood and hardwood pulp was 10% and 20% of the total acid content, respectively. The ratio of the two acids in pulps was not changed bq mannanase treatment, while xylanase treatment decreased the relative amount of the stronger acid. This indicates that the major part of the carboxylic groups are bound to xylan, Xylanase treatment removed about 30% of the xylan in both birch and pine pulps and, consequently 22% of the acid groups in hardwood pulp but only 8% of the acid groups in softwood pulp. Hence, in softwood kraft pulp fibres the content of uronic acid side-groups in accessible xylan on the surfaces of the fibres is lower than that on the hardwood fibres.
    Original languageEnglish
    Pages (from-to)208-214
    Number of pages7
    JournalHolzforschung
    Volume50
    Issue number3
    DOIs
    Publication statusPublished - 1996
    MoE publication typeA1 Journal article-refereed

    Fingerprint

    Unbleached pulp
    Kraft pulp
    Polyelectrolytes
    Titration
    Softwoods
    Hardwoods
    Pulp
    Xylans
    Adsorption
    Acids
    Fibers
    Uronic Acids
    Lignin
    Surface properties
    Enzymes

    Cite this

    Laine, Janne ; Buchert, Johanna ; Viikari, Liisa ; Stenius, Per. / Characterization of unbleached kraft pulps by enzymatic treatment, potentiometric titration and polyelectrolyte adsorption. In: Holzforschung. 1996 ; Vol. 50, No. 3. pp. 208-214.
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    abstract = "The surface properties of unbleached softwood (Pinus sylvestris) and hardwood (Betula verrucosa) kraft pulps were modified by treating the fibre surfaces with specific xylanase and mannanase (Trichoderma reesei). The amounts and accessibilities of surface carboxyl groups in untreated and enzyme-treated fibres were analyzed using adsorption of cationic polyelectrolytes and high precision potentiometric titration. According to the potentiometric titration both softwood and hardwood pulps contained two types of acidic groups, one with pK(1) approximate to 3.3 (uronic acid in xylan) and one with pK(2) approximate to 5.5 (probably carboxylic group in lignin), The relative amount of the weaker acid in softwood and hardwood pulp was 10{\%} and 20{\%} of the total acid content, respectively. The ratio of the two acids in pulps was not changed bq mannanase treatment, while xylanase treatment decreased the relative amount of the stronger acid. This indicates that the major part of the carboxylic groups are bound to xylan, Xylanase treatment removed about 30{\%} of the xylan in both birch and pine pulps and, consequently 22{\%} of the acid groups in hardwood pulp but only 8{\%} of the acid groups in softwood pulp. Hence, in softwood kraft pulp fibres the content of uronic acid side-groups in accessible xylan on the surfaces of the fibres is lower than that on the hardwood fibres.",
    author = "Janne Laine and Johanna Buchert and Liisa Viikari and Per Stenius",
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    Characterization of unbleached kraft pulps by enzymatic treatment, potentiometric titration and polyelectrolyte adsorption. / Laine, Janne; Buchert, Johanna; Viikari, Liisa; Stenius, Per.

    In: Holzforschung, Vol. 50, No. 3, 1996, p. 208-214.

    Research output: Contribution to journalArticleScientificpeer-review

    TY - JOUR

    T1 - Characterization of unbleached kraft pulps by enzymatic treatment, potentiometric titration and polyelectrolyte adsorption

    AU - Laine, Janne

    AU - Buchert, Johanna

    AU - Viikari, Liisa

    AU - Stenius, Per

    PY - 1996

    Y1 - 1996

    N2 - The surface properties of unbleached softwood (Pinus sylvestris) and hardwood (Betula verrucosa) kraft pulps were modified by treating the fibre surfaces with specific xylanase and mannanase (Trichoderma reesei). The amounts and accessibilities of surface carboxyl groups in untreated and enzyme-treated fibres were analyzed using adsorption of cationic polyelectrolytes and high precision potentiometric titration. According to the potentiometric titration both softwood and hardwood pulps contained two types of acidic groups, one with pK(1) approximate to 3.3 (uronic acid in xylan) and one with pK(2) approximate to 5.5 (probably carboxylic group in lignin), The relative amount of the weaker acid in softwood and hardwood pulp was 10% and 20% of the total acid content, respectively. The ratio of the two acids in pulps was not changed bq mannanase treatment, while xylanase treatment decreased the relative amount of the stronger acid. This indicates that the major part of the carboxylic groups are bound to xylan, Xylanase treatment removed about 30% of the xylan in both birch and pine pulps and, consequently 22% of the acid groups in hardwood pulp but only 8% of the acid groups in softwood pulp. Hence, in softwood kraft pulp fibres the content of uronic acid side-groups in accessible xylan on the surfaces of the fibres is lower than that on the hardwood fibres.

    AB - The surface properties of unbleached softwood (Pinus sylvestris) and hardwood (Betula verrucosa) kraft pulps were modified by treating the fibre surfaces with specific xylanase and mannanase (Trichoderma reesei). The amounts and accessibilities of surface carboxyl groups in untreated and enzyme-treated fibres were analyzed using adsorption of cationic polyelectrolytes and high precision potentiometric titration. According to the potentiometric titration both softwood and hardwood pulps contained two types of acidic groups, one with pK(1) approximate to 3.3 (uronic acid in xylan) and one with pK(2) approximate to 5.5 (probably carboxylic group in lignin), The relative amount of the weaker acid in softwood and hardwood pulp was 10% and 20% of the total acid content, respectively. The ratio of the two acids in pulps was not changed bq mannanase treatment, while xylanase treatment decreased the relative amount of the stronger acid. This indicates that the major part of the carboxylic groups are bound to xylan, Xylanase treatment removed about 30% of the xylan in both birch and pine pulps and, consequently 22% of the acid groups in hardwood pulp but only 8% of the acid groups in softwood pulp. Hence, in softwood kraft pulp fibres the content of uronic acid side-groups in accessible xylan on the surfaces of the fibres is lower than that on the hardwood fibres.

    U2 - 10.1515/hfsg.1996.50.3.208

    DO - 10.1515/hfsg.1996.50.3.208

    M3 - Article

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    JO - Holzforschung

    JF - Holzforschung

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