Abstract
Carboxylic acid bound to xylans in the fibre matrix cause a pH gradient between the fibre and the surrounding solution, known as the Donnan effect. The gradient is dependent on the ionic strength of the fibre solution. When meta1-free kraft pulp was used as a substrate for the Trichoderma reesei xylanase, the apparent pH optimum of the xylanase at low ionic strengths was found to be significantly higher, around 9, when a monovalent hydroxide was used for pH adjustment, as compared to the pH optimum obtained with a divalent metal hydroxide, i.e. pH 5–6. By increasing the ionic strength of the pulp solution by salt addition, the pH optimae of the xylanase became 5–6 with all the hydroxides. This difference was caused by the Donnan effect. Thus, at low ionic strengths the actual pH is lower than that measured in the solution, resulting in an increased apparent pH optimum of the xylanase. In practice, these results are important when applying xylanases on practical, fibre bound substrates, such as kraft pulps.
| Original language | English |
|---|---|
| Pages (from-to) | 217 - 222 |
| Number of pages | 6 |
| Journal | Journal of Biotechnology |
| Volume | 57 |
| Issue number | 1 - 3 |
| DOIs | |
| Publication status | Published - 1997 |
| MoE publication type | A1 Journal article-refereed |
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Impact of the Donnan effect on the action of xylanases on fibre substrates. / Buchert, Johanna (Corresponding Author); Tamminen, Tarja; Viikari, Liisa.
In: Journal of Biotechnology, Vol. 57, No. 1 - 3, 1997, p. 217 - 222.Research output: Contribution to journal › Article › Scientific › peer-review
TY - JOUR
T1 - Impact of the Donnan effect on the action of xylanases on fibre substrates
AU - Buchert, Johanna
AU - Tamminen, Tarja
AU - Viikari, Liisa
PY - 1997
Y1 - 1997
N2 - Carboxylic acid bound to xylans in the fibre matrix cause a pH gradient between the fibre and the surrounding solution, known as the Donnan effect. The gradient is dependent on the ionic strength of the fibre solution. When meta1-free kraft pulp was used as a substrate for the Trichoderma reesei xylanase, the apparent pH optimum of the xylanase at low ionic strengths was found to be significantly higher, around 9, when a monovalent hydroxide was used for pH adjustment, as compared to the pH optimum obtained with a divalent metal hydroxide, i.e. pH 5–6. By increasing the ionic strength of the pulp solution by salt addition, the pH optimae of the xylanase became 5–6 with all the hydroxides. This difference was caused by the Donnan effect. Thus, at low ionic strengths the actual pH is lower than that measured in the solution, resulting in an increased apparent pH optimum of the xylanase. In practice, these results are important when applying xylanases on practical, fibre bound substrates, such as kraft pulps.
AB - Carboxylic acid bound to xylans in the fibre matrix cause a pH gradient between the fibre and the surrounding solution, known as the Donnan effect. The gradient is dependent on the ionic strength of the fibre solution. When meta1-free kraft pulp was used as a substrate for the Trichoderma reesei xylanase, the apparent pH optimum of the xylanase at low ionic strengths was found to be significantly higher, around 9, when a monovalent hydroxide was used for pH adjustment, as compared to the pH optimum obtained with a divalent metal hydroxide, i.e. pH 5–6. By increasing the ionic strength of the pulp solution by salt addition, the pH optimae of the xylanase became 5–6 with all the hydroxides. This difference was caused by the Donnan effect. Thus, at low ionic strengths the actual pH is lower than that measured in the solution, resulting in an increased apparent pH optimum of the xylanase. In practice, these results are important when applying xylanases on practical, fibre bound substrates, such as kraft pulps.
U2 - 10.1016/S0168-1656(97)00101-6
DO - 10.1016/S0168-1656(97)00101-6
M3 - Article
VL - 57
SP - 217
EP - 222
JO - Journal of Biotechnology
JF - Journal of Biotechnology
SN - 0168-1656
IS - 1 - 3
ER -