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  • 1
    Electronic Resource
    Electronic Resource
    Enzymatic accessibility of xylans in lignocellulosic materials (1994)
    Springer
    Applied microbiology and biotechnology 41 (1994), S. 124-129 
    Details
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract. The hydrolysis of fibre-bound and isolated xylans from both birch and pine wood and kraft pulps was studied using purified xylanolytic enzymes of Trichoderma reesei. Despite high enzyme loading, the degree of hydrolysis of fibre-bound substrates did not exceed 20% of the theoretical value, apparently due to limited accessibility of the substrates. The fibre-bound xylans were as equally accessible in softwood as in hardwood pulps. The isolated xylans of wood and kraft pulps could be solubilized more extensively, with a hydrolysis yield of 50–65%. The substitution degree of the isolated xylan substrates was reflected in the different hydrolysis yields obtained by the two xylanases, with isoelectric point (pI) values of 9.0 and 5.5. On the more substituted substrates, i.e. pine kraft xylan and pine wood xylan, the two enzymes acted almost similarly, whereas on the less substituted xylan substrates, such as isolated birch kraft xylan, the pI-9.0 enzyme was more efficient. The side-group-cleaving enzymes increased only moderately the solubilization of the substrates.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00166093
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  • 2
    Electronic Resource
    Electronic Resource
    Enzymatic deacetylation of galactoglucomannans (1993)
    Springer
    Applied microbiology and biotechnology 39 (1993), S. 159-165 
    Details
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Several hemicellulolytic microorganisms were screened for their capability of liberating acetyl side groups from native softwood galactoglucomannan. All the microorganisms tested were found to produce an extracellular acetyl glucomannan esterase(s). The highest activity was detected in Schizophyllum commune culture filtrate. However, the enzyme produced by Aspergillus oryzae was most efficient in long-term hydrolysis. Acting alone, the purified esterase of A. oryzae was able to liberate most of the acetic acid from galactoglucomannan. The addition of other galactoglucomannan-degrading enzymes did not affect the action of esterase. On the other hand, the addition of esterase clearly enhanced the action of mannanase and α-galactosidase. The purified acetyl esterase of Trichoderma reesei was able to liberate acetic acid from short oligomers of glucomannan, whereas the acetyl xylan esterase of T. reesei was unable to act on glucomannan oligomers of any size.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00228600
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Enzymatic accessibility of xylans in lignocellulosic materials (1994)
    Springer
    Applied microbiology and biotechnology 41 (1994), S. 124-129 
    Details
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract The hydrolysis of fibre-bound and isolated xylans from both birch and pine wood and kraft pulps was studied using purified xylanolytic enzymes of Trichoderma reesei. Despite high enzyme loading, the degree of hydrolysis of fibre-bound substrates did not exceed 20% of the theoretical value, apparently due to limited accessibility of the substrates. The fibre-bound xylans were as equally accessible in softwood as in hardwood pulps. The isolated xylans of wood and kraft pulps could be solubilized more extensively, with a hydrolysis yield of 50–65%. The substitution degree of the isolated xylan substrates was reflected in the different hydrolysis yields obtained by the two xylanases, with isoelectric point (pI) values of 9.0 and 5.5. On the more substituted substrates, i.e. pine kraft xylan and pine wood xylan, the two enzymes acted almost similarly, whereas on the less substituted xylan substrates, such as isolated birch kraft xylan, the pI-9.0 enzyme was more efficient. The side-group-cleaving enzymes increased only moderately the solubilization of the substrates.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00166093
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    Paper (German National Licenses)
    Fulltext
  • 4
    Electronic Resource
    Electronic Resource
    The hydrolysis of steamed birchwood hemicellulose by enzymes produced byTrichoderma reesei andAspergillus awamori (1986)
    Springer
    Applied microbiology and biotechnology 23 (1986), S. 487-490 
    Details
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary The hemicellulase separated from birchwood by steaming and water extraction comprised mainly of acetyl- and 4-O-methyglucurono-substituted xylo-oligomers. The liberation of the acidic side groups affected the rate and yield of the enzymatic hydrolysis of the xylo-oligomers. The hemicellulase ofTrichoderma reesei was superior to that ofAspergillus awamori both with respect to side group cleavage and xylose yield in hydrolysis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02346065
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  • 5
    Electronic Resource
    Electronic Resource
    Comparison of Pseudomonas fragi and Gluconobacter oxydans for production of xylonic acid from hemicellulose hydrolyzates (1988)
    Springer
    Applied microbiology and biotechnology 28 (1988), S. 367-372 
    Details
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary Xylonic acid was produced efficiently from pure xylose by Pseudomonas fragi ATCC 4973 and Gluconobacter oxydans subsp. suboxydans ATCC 621. The yield from 10% xylose was in both cases over 95% of the theoretical. However, the sensitivities of the strains towards the major inhibitors found in hemicellulose hydrolyzates, ie. acetic acid, furfural and two lignin-derived compounds, varied. G. oxydans tolerated all these inhibitors better than P. fragi. In tests using steamed hemicellulose hydrolyzate, G. oxydans was able to utilize the substrate only at dilute xylose concentrations. After ether extraction or mixed bed resin pretreatment, the fermentability of the hydrolyzate was increased significantly.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00268197
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  • 6
    Electronic Resource
    Electronic Resource
    Biotechnical utilization of wood carbohydrates after steaming pretreatment (1985)
    Springer
    Applied microbiology and biotechnology 22 (1985), S. 416-423 
    Details
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary Birch wood was used as raw material to study the effect of steaming pretreatment on the characteristics, enzymatic hydrolysis and fermentation of cellulose and hemicellulose. The cellulose remained undissolved in the fibres after steaming, but the degree of polymerization decreased and the surface area increased with increasing steaming temperature. The yield in enzymatic hydrolysis with T. reesei and A. niger cellulases increased from 40 to 75% of theoretical when the pretreatment temperature was increased from 170 to 210°C at a residence time of 10 minutes. The glucose released was fermented to ethanol by yeast without interference of toxic compounds. After steaming, the hemicellulose was mainly in the form of xylo-oligomers. The average chain length decreased with increasing temperature. Only the monomeric sugars were fermented to ethanol by Fusarium oxysporum. After steaming at 210°C toxic decomposition products inhibited the fermentation completely. In aerobic conditions also the xylo-oligomers were metabolized.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00252783
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  • 7
    Electronic Resource
    Electronic Resource
    Characteristics of Trichoderma reesei β-xylosidase and its use in the hydrolysis of solubilized xylans (1988)
    Springer
    Applied microbiology and biotechnology 28 (1988), S. 425-432 
    Details
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary The β-xylosidase (EC 3.2.1.37) of Trichoderma reesei was purified and its characteristics and use in the hydrolysis of steamed birch xylan were studied. The enzyme was a glycoprotein with a molecular weight of 100000 as determined by SDS-gel electrophoresis and its isoelectric point was 4.7. The pH optimum was 4.0 and temperature optimum 60°C. β-Xylosidase was competitively inhibited by xylose and the inhibition constant was 2.3 mM. The purified enzyme also showed α-arabinofuranosidase activity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00268208
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  • 8
    Electronic Resource
    Electronic Resource
    Characterisation of regioselectively functionalized 2,3-O-carboxymethyl cellulose by enzymatic and chemical methods (2000)
    Springer
    Cellulose 7 (2000), S. 161-175 
    Details
    ISSN: 1572-882X
    Keywords: 2,3-O-carboxymethyl cellulose ; molar mass distribution ; endoglucanase hydrolysis ; anion exchange chromatography ; distribution of functional groups
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract The determination of the molecular structure of 2,3-O-carboxymethyl cellulose (2,3-O-CMC), prepared via 6-O-(4-monomethoxy)triphenylmethyl cellulose, was carried out in detail by means of enzymatic and chemical methods. The 2,3-O-CMCs had degrees of substitution (DS) in the range of 0.5–1.2 showing a narrow molar mass distribution as revealed by SEC. As a result of an endoglucanase treatment, an intensive depolymerization of the samples occurred which was more pronounced for 2,3-O-CMC with comparatively low DS. All degraded samples could be separated into 18 fractions by preparative SEC and the proportion of each individual repeat unit was analysed by anion exchange chromatography (AEC) following complete hydrolytic chain degradation. The results indicated a homogeneous distribution of the functional groups within the polymer chain. Moreover, it became obvious that a preferred carboxymethylation of O-2 compared with O-3 occurred and that a preferred functionalization of already carboxymethylated units occurred as the reaction progressed. AEC with pulsed amperometric detection, which was used to separate and analyse the differently functionalized repeating units as well as glucose, had to be calibrated. Therefore, a method to determine the response factors of the individual carboxymethylated glucose units was developed using 13C NMR spectroscopic measurements (inverse gated decoupling) of depolymerised 2,3-O-CMC.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009249224441
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  • 9
    Electronic Resource
    Electronic Resource
    Biochemical characteristics of two endo-β-1,4-xylanases produced byPenicillium capsulatum (1993)
    Springer
    Journal of industrial microbiology and biotechnology 11 (1993), S. 171-180 
    Details
    ISSN: 1476-5535
    Keywords: Penicillium capsulatum ; Xylan ; Xylanases ; Hydrolysis product
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary Two endo-β-1,4-xylan xylanohydrolases (EC 3.2.1.8), XynA and XynB, from solid-state cultures ofPenicillium capsulatum, were purified to apparent homogeneity as judged by electrophoresis and isoelectric focusing. Each is a single subunit glycoprotein. XynA containing 97 mol carbohydrate·mol−1 protein, while XynB contains 63 mol·mol−1.M r and pI values are 28 500, 5.0–5.2 (XynA) and 29 500, 5.0–5.2 (XynB), respectively. Both enzymes are most active at pH 4 and 47–48°C, and have half-lives of 32 min (XynA) and 13 min (XynB) at pH 4, 60°C. Each form catalyzed the hydrolysis of a variety of xylans, albeit with different degrees of efficiency. In addition, XynB catalyzed extensive degradation of barley β-glucan, CM-cellulose and, to a lesser extent, lichenan, but kinetic parameters indicate that it is primarily a xylanase. The products of hydrolysis of various xylans and xylopentaose differed for each enzyme and ranged from xylose to xyloheptaose depending on the substrate used. Each enzyme is endo-acting and has transferase as well as direct hydrolase activity. Inactivation byN-bromosuccinimide indicated the possible involvement of tryptophan in binding and/or catalysis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01583719
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  • 10
    Electronic Resource
    Electronic Resource
    Evaluation of hydrolysis products of xylans by xylan-degrading enzymes from Humicola grisea var. thermoidea and Aspergillus fumigatus Fresenius (2000)
    Springer
    World journal of microbiology and biotechnology 16 (2000), S. 81-83 
    Details
    ISSN: 1573-0972
    Keywords: Hydrolysis products ; transglycosidase activity ; xylan ; xylanase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Xylan-degrading enzyme activities were isolated from crude extracts of solid-state cultures of Aspergillus fumigatus Fresenius (Xyl I, Xyl III, Xyl IV and Xyl V) and Humicola grisea var. thermoidea (Xyl II) by chromatographic procedures. The pattern of hydrolysis of different xylans and pulps varied from traces of xylose to xylooligomers. The products formed suggest an endo-type enzyme mode of action. Some enzymes showed debranching and transglycosidase activities.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008954607205
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