ISSN:
1432-0614
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
,
Process Engineering, Biotechnology, Nutrition Technology
Notes:
Abstract Treating kraft pulps with the crude xylanase from Streptomyces roseiscleroticus followed by alkali extraction reduces the kappa number in a linear manner with enzyme doses up to about 3 IU/gm of oven-dry pulp. The enzyme complex consists of four isoenzymes designated Xyl1, Xyl2, Xyl3 and Xyl4. Each can release chromophores when used alone and each can facilitate alkali extraction to reduce the kappa number, but their relative abilities are different. Of the four isozymes, Xyl4 releases the least color and 237-nm-absorbing material whereas Xyl3 releases the most. Xyl4 best enhances the ability of alkali to reduce the kappa number. The UV absorption spectrum of the material released by alkali extraction differs significantly from the spectral characteristics of that released during enzyme treatment. The alkali-solubilized material has a maximum absorptivity at 265 nm and relatively little absorptivity at 237 nm. The material released during enzyme treatment absorbs strongly at 205 and 237 nm. UV/VIS spectroscopy of the enzyme- or alkali-released material does not show a characteristics lignin peak at 280 nm, nor does it reveal any notable peaks in the visible region. Analysis of the material released by enzyme treatment revealed more than 40 product peaks after fractionation by reversed-phase HPLC. We observed many products with strong UV absorption. These were relatively hydrophilic. Fewer products absorbed in the visible region. These were more hydrophobic. All four isoenzymes exhibit endo-action patterns; none forms xylose from oat-spelt xylan. The action patterns fell into two groups: endo-1 enzymes (Xyl1 and Xyl3) formed xylotriose (X3) and other lower oligosaccharides as the predominant products; endo-2 enzymes (Xyl2 and Xyl4) formed roughly equimolar amounts of X3, xylotetraose (X4), and xylopentaose (X5), and tended to leave larger amounts of undigested higher oligosaccharides.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00192102
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