Kyoko S. Katsumata

Structural changes in lignin of tropical woods during digestion by termite, Cryptotermes brevis

Wood samples of apitong (Dipterocarpus grandiflorua) and ilang-ilang (Ilang-Ilang C. dadloyi) and feces of termites [Cryptotermes brevis (Walker)] fed on these woods were collected from University of the Philippines, Los Baňos. Lignin of each sample was isolated by Björkman’s procedure. There was no significant difference in 1H nuclear magnetic resonance (NMR) spectra or in the methoxyl content between Björkman lignins from original woods and termite feces. Differences were detected in the contents of aliphatic and unconjugated phenolic hydroxyl groups, suggesting minor structural changes of lignin during digestion by termites. In addition, the ratio of syringyl to guaiacyl nuclei of Björkman lignin from termite feces determined by 1H NMR spectra was higher than those from the original woods. The molar ratio of syringyl to guaiacyl nuclei of termite feces was higher than those from the original woods as determined by alkaline nitrobenzene oxidation. These results suggest that the structural changes of lignin in the termite gut are due to the insignificant formation of C-C linkages in guaiacyl nuclei. It was concluded that there were minor changes in the structural features of lignin under mostly anaerobic conditions, in contrast to the significant changes that occur through biological modification under aerobic conditions.

Reduction of aluminum toxicity to radish by alkaline oxygen treated kraft lignin

To obtain a soil-conditioning agent for acid soil containing excess aluminum ions (AL), kraft lignin was modified by alkaline oxygen treatment. The growth of radish root in solution and in soil containing AL with or without addition of these lignins under controlled pH was examined. We concluded the following. Growth inhibition of radish roots by AL can be removed by adding alkaline oxygentreated lignins in the range of pH 4.5–4.8 in soil. A similar result was obtained at pH 4.5 in a culture solution. The reduction of AL toxicity to plant may be due to the aggregation between AL and the modified lignin at low concentrations of modified lignin because soluble AL could not be detected. On other hand, elongation of radish root was not obviously inhibited, although the soluble AL in the solution culture was at an extremely high level when the dosage of a modified lignin was high. This suggests that the reduction in AL toxicity to plants was due to formation of a complex between AL and acidic groups of the modified lignin.

Modified Kraft Lignin and Its Use for Soil Preservation

The rapid decrease of forest land in the world, particularly that of the tropical rain forest, is a matter of most concern to us. According to a recent report, 1,690 x 104 hectares of tropical rain forest are disappearing every year due to increase in forest burning and timber production. Although tropical rain forest has extremely high biomass productivity when it is in sound conditions, its ecosystems are not necessarily very tolerant to drastic changes to their conditions. Once a forest is lost for some reason(s), reforestation may be difficult due to acidic or other poor soil conditions.

Lignin characteristics of peculiar vascular plants

Trochodendron aralioides Sieb. et Zucc. and Chloranthus glaber (Thunb.) Makino [Sarcandra globra (Thunb.) Nakai] belong to primitive angiosperms, and are characterized by the absence of vessels. Ephedra sinica Stapf, which is classified in the gymnosperms, contains vessel elements and fiber together with tracheids. Podocarpus macrophyllus (Thunb. Ex Murray) D. Don var. macrophyllus is reported to give a weak positive Mäule test, although it is classified as a gymnosperm. Podocarpus macrophyllus gave only vanillin on alkaline nitrobenzene oxidation, while E. sinica, T. aralioides, and C. glaber gave both vanillin and syringaldehyde. The molar ratio of syringyl to guaiacyl nuclei (S/V ratio) of C. glaber was significantly low (S/V = 0.08) in comparison with the value for T. aralioides (S/V = 1.56). The erythro form is the predominant diasteromeric form of β-O-4 intermonomer linkages of T. aralioides and E. sinica [molar ratio of erythro to threo forms (E/T ratio): 1.93 and 1.67, respectively]; however, P. macrophyllus and C. glaber lignins, of which S/V ratios were 0 and 0.08, gave approximately equal amounts of erythro and threo forms (E/T ratio: 1.01 and 1.14). Results from 1H NMR spectroscopy agree well with S/V ratios of alkaline nitrobenzene oxidation and E/T ratios of ozonation products. In conclusion differences in guaiacyl lignin and guaiacyl-syringyl lignin do not exactly reflect taxonomical differences, as reported in previous articles. It was found that guaiacyl-syringyl lignin is not necessarily linked to the presence of vessels.

Characterization of lignin fragments in alkaline oxygen-stage waste liquor as soil-conditioning agent

We characterized the lignin fragments in the alkaline oxygen delignification-stage waste liquor from a pulp and paper mill as a soil-conditioning agent. Chemical reactions of this lignin fragment should be very similar to those of alkaline-oxygen treatment of kraft lignin. Alkaline oxygen delignification-stage waste liquor was subjected to gel filtration chromatography and four different molecular weight fractions (F1, F2, F3, and F4) were obtained. These four fractions were used in plant growth experiments. A very clear positive effect in removing the aluminum (Al) toxicity to root growth of radish was found for all four fractions. When aluminum concentration in the nutrient solution was as low as 0.5 ppm, root elongation was practically inhibited, but if 12.5 ppm of lignin fragment was added, the toxic effect was practically removed and root elongation better than that in the control was observed. However, each fraction showed different performance in removing aluminum toxicity, and the highest molecular weight fraction, which contained some aromatic structures, showed better performance in removing Al toxicity. The reason for their different behaviors on Al toxicity was also examined.

Mechanism of detoxification of aluminum ions by kraft lignin treated with alkaline oxygen

Abstract Kraft lignins modified by radical sulfonation or alkaline oxygen treatment were rich in acidic groups, such as sulfonic acid, carboxylic acid, and phenolic hydroxyl groups, and were effective as soil-conditioning agents, especially because of their ability to trap aluminum ions eluted from soil under acidic conditions. Formation of complexes between aluminum ions and modified lignins was examined using potentiometric titration and 27Al nuclear magnetic resonance (NMR) spectroscopy. Changes in the titration curve of a modified lignin by the addition of aluminum ions suggest the release of protons after the formation of complexes between them. Disappearance of 27Al-NMR signals assigned to various aluminum ions by the addition of kraft lignin treated with alkaline oxygen was also attributed to the formation of complexes. The relative ease of proton release because of complex formation between a modified lignin and metal ions was as follows: Fe3+ > Al3+ > Cu2+ > Pb2+ > Mn2+ > Ca2+. This indicates that aluminum complexes are quite stable, and the aluminum ion is not exchanged with cations other than Fe3+.

Effect of low molecular weight lignin fragments including oxalic acid in alkaline-oxygen stage waste liquor on Al toxicity

Our previous study indicated the existence of some low molecular weight contaminants in separated fractions (F1 to F4) of alkaline-oxygen stage waste liquor by spectroscopic analysis. In the present study, the quantities of these compounds were determined by capillary electropheresis (CE). Substantial amounts of oxalate and acetate were found in F3. The complexes between Al and oxalate as well as F3 were characterized by 27Al-nuclear magnetic resonance (NMR) spectroscopy, and the spectra of Al-oxalate complexes demonstrated the ability of oxalate to chelate Al and to produce different forms of complexes at varied molar ratios. Plant growth experiments in the presence of Al-oxalate complexes suggested that at a proper range, oxalate has a favorable effect on the detoxification of Al toxicity. It can be assumed that oxalate in F3 also plays an important role in the efficiency of removing Al toxicity. 27Al-NMR was proved to be a useful method for the study of complexes between Al and organic compounds without disturbing their equilibrium conditions.

INSERTION-ACCELERATED AGEING TEST OF PAPER FOR CONSERVATION: INCREASE IN DISCOLOURATION OF ACID AND ALKALINE PAPER INTERFACE

Abstract Alkaline papers are used for preference in the conservation field, except with alkali-sensitive materials, since it is supposed that alkaline paper has beneficial effects for the preservation of acidic paper. The moist heat ageing of paper by the commonly used method of suspending paper in an oven was compared with an insertion method in which the test paper was inserted into books made of other types of paper. Alkaline paper increased the durability of acidic paper. However, some types of acidic paper were severely discoloured by insertion into a book of alkaline paper. This result shows that neutral paper might be preferable for use as envelopes for acidic paper, and that moist heat ageing by the insertion method is a valuable technique for the evaluation of conservation paper.

THE PERMANENCE OF TRADITIONAL CHINESE PAPER

Traditional Chinese paper is still used in painting and calligraphy today, and it is also an important material for restoration of ancient works. Although it is said that xuan paper, one of the best Chinese papers, can last over 1000 years, research on the permanence of Chinese paper is not yet sufficient. In recent years, cheap materials, such as Chinese alpine rush (longxu cao) and woodpulp, have often been used, and the use of stronger chemicals for processing and of bleaching chemicals is also common. Changes in the materials and papermaking processes may harm the permanence of paper. In this research, seven kinds of traditional Chinese paper for painting and calligraphy were selected as samples to investigate their strength and durability after accelerated ageing (80°C, 65% RH).