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1.
2.
A new capillary electrophoretic (CE) technique was developed for the separation of lignin degradation products after permanganate oxidation, yielding information about quality and quantity of various linkages in the lignin molecule. This CE method is a promising alternative to existing gas chromatographic (GC) methods. An advantage in comparison with GC is the short separation time and the fact that the oxidation products (aromatic acids) can be analyzed without derivatization. The selectivity and sensitivity of CE combined with UV detection is adequate and makes it suited for fast routine characterization of lignins. If necessary, the CE method can be coupled with electrospray ionization mass spectrometry in order to make a clear assignment of the peaks. 相似文献
3.
Enzymatic degradation of two lignin-based polymers (lignophenols), lignocatechol and lignocresol, prepared by selectively grafting catechol and p-cresol to Cα positions of lignin, respectively, were carried out in aqueous organic solvents. Both lignophenols showed high reactivity in the peroxidase-catalyzed oxidation. Structural analyses by NMR spectroscopies revealed that the degraded lignophenols contained aliphatic chain content, which might be mainly formed in the reduction of the intermediate initially generated by the aromatic ring cleavage. Lower amount of aromatic units in the lignophenols after degraded by peroxidase also indicted the cleavage of aromatic rings. Due to the substitution of phenols at Cα positions of lignin, the degraded lignophenols did not have carbonyl structure, which was abundant in the biodegradation products of native lignin. The two lignophenols were also degraded by Rhus vernicifera laccase. But the degree of degradation was lower than that of the degradation by peroxidase, which might be due to the low activity of laccase on the lignin moieties in lignophenols. 相似文献
4.
Raquel F. P. Nogueira Ronaldo A. Pilli Nelson durÁn 《Applied biochemistry and biotechnology》1992,33(3):169-176
Growth of the ascomyceteChrysonilia sitophila during degradation of lignin model dimers and monomers was compared to a glucose control. An inhibition of growth by Cα-carbonyl
monomers and stimulation by β-O-4 lignin model and vanillyl alcohol were observed. A comparison of the degradation by this
ascomycete with the basidiomycetePhanerochaete chrysosoporium showed similarities in relation to the type of degradation caused. 相似文献
5.
Patricia MerdyEmmanuel Guillon Jacques DumonceauMichel Aplincourt 《Analytica chimica acta》2002,459(1):133-142
Comparative studies using various analytical and spectroscopic techniques have been carried out on three samples of lignin: two samples of natural lignin that have been extracted using different processes, and one sample of synthetic lignin. This paper discusses the general features common to all three kinds of lignin, as well as the differences between, on one hand, the two natural lignins coming from different extraction processes, and, on the other hand, the natural lignins and the synthetic one. The advantages of each technique in explaining the structure of these three different lignins are emphasised. 相似文献
6.
Thyme (Thymus vulgaris) has been known, long time ago, for its aromatic properties. It contains essential oils and polymers such as cellulose (mixture of hemicellulose and cellulose) and lignin. The thyme, studied in this work, was gathered from the same place, in the period from November 1999 to October 2000. The chemical analysis (water, total ash, essential oils, extractive substances, cellulose, holocellulose and lignin) can be used roughly in the characterisation of the four periods that correspond to the four seasons of the year. The cellulose level was found to be more than lignin level in the wet periods (growth of the plant). The opposite was found in the dry periods. The total ash and essential oil levels were found to be high during the period of high pluviometry. The thermal decomposition of cellulose and holocellulose was found to fit well with the first-order kinetics. The activation energy, under air flow, was 185 and 196 kJ mol−1 for cellulose and holocellulose, respectively. The maximum decomposition rate and thermal analysis heating rate of lignin were found to have a direct linear relationship. 相似文献
7.
Grzegorz Milczarek 《Electroanalysis》2007,19(13):1411-1414
Alkali lignin undergoes strong adsorption on polycrystalline gold electrodes. Subsequent oxidation in a sulfuric acid solution leads to a restructured redox‐active polymer that shows features characteristic for surface confined species. Surface coverage of up to 4.40×10?10 mol cm?2 may be obtained depending on the adsorption time or lignin concentration in the adsorption solution. Using Laviron's approach the electron‐transfer rate constant and the transfer coefficient were found to be 8.9 s?1 and 0.35, respectively. The formal potential of the redox couple shifted negatively with pH at a rate of ca. 60 mV/pH unit, suggesting a 2 e/2 H+ reaction. The redox couple was also found to be a good mediator for electrochemical ascorbic acid oxidation in neutral phosphate buffer with ca. 250 mV reduction of the oxidation overpotential. 相似文献
8.
Gabriela M. M. Calabria Adilson R. Gonçalves 《Applied biochemistry and biotechnology》2006,129(1-3):320-325
Oxidation of lignin obtained from acetosolv and ethanol/water pulping of sugarcane bagasse was performed by phenol oxidases:
tyrosinase (TYR) and laccase (LAC), to increase the number of carbonyl and hydroxyl groups in lignin, and to improve its chelating
capacity. The chelating properties of the original and oxidized lignins were compared by monitoring the amount of Cu2+ bound to lignin by gel permeation chromatography. The Acetosolv lignin oxidized with TYR was 16.8% and with LAC 21% higher
than that of the original lignin. For ethanol/water lignin oxidized with TYR was 17.2% and with LAC 18% higher than that of
the original lignin. 相似文献
9.
The effect of carbon and nitrogen sources, lignocellulosic substrates, and metal ions on lignin peroxidase (LiP) activity
of Aspergillus sp., which was isolated from a mangrove area, was studied. Glucose (1%) was found to be the best carbon source. Among the
various lignocellulosic substrates used, coir pith at 3% concentration increased LiP activity twofold on the second day of
incubation. Peptone and KNO3 completely inhibited the enzyme synthesis while (NH4)2SO4 at 12.5 mM produced maximum activity. Since seawater contained all the requisite metal ions, any added ions had a negative effect on
activity. Cu2+ had the most inhibiting effect while K+ the least. When all the optimized conditions were provided, in nitrogen- and carbon-sufficient medium, a maximum LiP activity
of 345 U/mL was obtained on the second day of incubation. 相似文献
10.