Alteration Of Lignin Research Articles

Soil organic matter and its lignin component in surface horizons of salt-affected soils of the Argentinian Pampa

Salt-affected soils differ in their chemical properties to all other soils. Sodicity and salinity may affect the soil organic matter component of these soils. In a field experiment, we investigated organic matter decomposition in nonsaline nonsodic Aquic Argiudoll, a nonsaline sodic Typic Natraquoll, nonsaline nonsodic Petrocalcic Paleudoll and a saline sodic Typic Natralboll in the Pampa Deprimida, Argentina. The objectives were to identify the degree of stabilization of organic matter by association with mineral particles in these soils and to follow in particular the fate of lignin in these soils. We measured organic carbon, total nitrogen and the extent of lignin alteration with soil depth and in various particle size fractions. The salt-affected soils contained much less organic carbon and nitrogen in their mollic epipedons than the nonsaline nonsodic soils, and bioturbation into deeper layers was restrained. In the salt-affected soils most of the organic matter was in sand-sized particles. Retarded degradation of plant residues was indicated by the pattern of lignin-derived phenols, suggesting less alteration of lignin in the salt-affected soils than in the nonsaline nonsodic soils. We suggest that this results from the effects of high pH, high sodicity, and high salinity on the microorganisms and their enzymatic activities. The high pH and high concentrations of monovalent cations decreased formation of solid organo-mineral complexes. We conclude that in the salt-affected soils oxidatively altered organic compounds are susceptible to losses in dissolved or colloidal forms, because these compounds are not stabilized against leaching and mineralization by chemical bonding to soil minerals.

Cupric oxide oxidation products of tropical peat soils

Cupric oxide oxidation was used in order to examine the composition of lignin-derived phe nolic compounds and to estimate the degree of lignin alteration of tropical peat soils. KVila's pyrophosphate index (PPI) was used to assess the degree of decomposition of peat soils. Tropical peat soil samples were collected from soil profiles in three areas of Indone sia including of 11 sites, located in reclaimed / cultivated areas and under forest stands. Ox idation of these samples produced vanillyl and syringyl phenols as major components while cinnamyl phenol as a minor component. Phenolic aldehydes almost always predominated, followed by phenolic acids, ugh correlations between the yield of the oxidation products and PPI suggested that lignin-derived oxidation products could be used to describe the alteration of lignin in tropical peat soils, Based on the samples studied, two groups of lignin alteration with depth were recognized, which could be best described by acid to aldehyde ratios. The first group was observed in inland peat soils associated with a relatively more anaerobic history of alteration in the lower layers and the second group in marginal peat soils. The pattern of lignin alteration with depth also revealed that reclamation/cultivation mostly affected the surface layers to a depth of about 40 cm.

Contribution of lignin and polysaccharides to the refractory carbon pool in C-depleted arable soils

We assessed the contribution of polysaccharides and lignin, major components of plant residues, to the refractory pool of soil organic carbon (SOC) in arable soils. Soil samples from two contrasting treatment types of European long-term agroecosystem experiments, i.e. conventionally managed (fertilized) and C-depleted plots, enriched in refractory compounds, were compared. Bulk samples from eight experimental sites and particle-size fractions of two of the sites were investigated. The CuO oxidation technique was used as a relative measure of lignin and its degree of structural alteration. The contents and composition of polysaccharides were determined following hydrolysis with trifluoroacetic acid (TFA). For the bulk samples, the amount of lignin phenols declined more than the total OC in the course of C-depletion. The contribution of lignin phenols to total OC was thus lower in the C-depleted versus the fertilized plots. A greater lignin biodegradation was found in the bulk samples of the depleted plots compared with the fertilized plots. The analysis of size fractions revealed lower OC-normalized contents of lignin phenols and a higher degree of lignin alteration in fractions <63 μm of the depleted versus the fertilized plots. These findings indicate that lignin does not accumulate within the refractory C pool of arable soils. The refractory SOC pool shows a lower contribution of lignin as compared with more labile fractions of SOC. If lignin-derived carbon is present in the stable pool it has been extensively modified so that it can no longer be identified as phenolic CuO oxidation products. OC-normalized contents of polysaccharides (neutral sugars and galacturonic acid) were similar in bulk samples of the C-depleted and fertilized plots. The contrasting treatments showed similar polysaccharide contents especially in separates <6 μm. The separates <6 μm in the C-depleted plots retained between 50 and 100% of the polysaccharide amounts in the fertilized plots. The mass ratio of (galactose+mannose)-to-(arabinose+xylose) (GM/AX) was higher in bulk samples of the C-depleted versus the fertilized plots, indicating a higher relative contribution of microbial sugars. Within a particular soil, the fine separates were those with the highest GM/AX ratio. These results indicate that the refractory C pool has a similar proportion of polysaccharides as the labile C pool, but refractory polysaccharides are mainly associated with fine separates and show a dominant contribution of microbial sugars. Our results provide evidence that polysaccharides, mainly those of microbial origin, are stabilized over the long-term within fine separates of arable soils. In contrast, CuO lignin is associated mainly with the coarse fractions and does not contribute to the refractory C pool.

Stable carbon isotopes of wood: a clue to palaeoclimate?

Detailed stable carbon isotope and molecular investigations were undertaken on a number of archaeological and fossil wood specimens to provide insights into their use as rigorous independent palaeoclimatic and palaeoenvironmental parameters. The isotope data revealed large differences amongst the material with the oldest specimens being least depleted in 13C. Although natural variation could account for some of the observed differences, the isotope values of the archaeological and Tertiary specimens are most probably related to the absolute abundance of polysaccharides present and the degree of lignin alteration. The molecular data, based on pyrolysis, of the Antarctic Cretaceous conifer specimens revealed only transformed lignin, with virtually no intact lignin building blocks (2-methoxyphenols) preserved, and no evidence of polysaccharides. This degree of chemical alteration is suggested here to be one of the main causes for the 13C enriched values of these conifer specimens. These results show the importance of combining detailed molecular information on individual wood components with stable carbon isotope data for palaeoclimatic and palaeoenvironmental studies.

Sources and composition of soil organic matter fractions between and within soil aggregates

SummaryIt is generally accepted that particulate organic matter derives from plants. In contrast, the enriched labile fraction is thought by many to derive from microbes, especially fungi. However, no detailed chemical characterization of these fractions has been done. In this study, we wanted to assess the sources (plants or microbes; fungi or bacteria) and degree of microbial alteration of (i) three particulate organic matter fractions – namely the free light fraction (1.85 g cm−3), the coarse (250–2000 μm) and the fine (53–250 μm) intra‐aggregate particulate organic matter fractions – and of (ii) three density fractions of fine‐silt associated carbon – namely &lt; 2.0, 2.0–2.2 (i.e. enriched labile fraction) and &gt; 2.2 g cm−3– by analysing the amino sugars, by CuO oxidation analyses, and by 13C‐, 1H‐ and 31P‐NMR analyses. Macroaggregates (250–2000 μm) were separated by wet‐sieving from a former grassland soil now under a no‐tillage arable regime. The three particulate organic matter fractions and the three density fractions were isolated from the macroaggregates by a combination of density flotation, sonication and sieving techniques. Proton NMR spectroscopy on alkaline extracts showed that the enriched labile fraction is not of microbial origin but is strongly degraded plant material that is enriched in aliphatic moieties partly bound to aromatics. In addition, the enriched labile fraction had a glucosamine content less than the whole soil, indicating that it is not enriched in carbon derived from fungi. Decreasing yields of phenolic CuO oxidation products and increasing side‐chain oxidation in the order coarse intra‐aggregate particulate organic matter &lt; fine inter‐aggregate particulate organic matter &lt; fine‐silt fractions indicate progressive alteration of lignin as particle size decreases. The light fraction was more decomposed than the coarse inter‐aggregate particulate organic matter, as indicated by (i) its larger ratio of acid‐to‐aldehyde of the vanillyl units released by CuO oxidation, (ii) the smaller contribution of H in carbohydrates to total extractable H as estimated by 1H‐NMR spectroscopy, and (iii) a larger contribution of monoester P to total extractable P in the 31P‐NMR spectra. In conclusion, the four fractions are derived predominantly from plants, but microbial alteration increased as follows: coarse inter‐aggregate particulate organic matter &lt; light fraction ≈ fine inter‐aggregate particulate organic matter &lt; enriched labile fraction.

A model for lignin alteration—part I: a kinetic reaction-network model

A new quantitative model is presented which simulates the maturation of lignin-derived sedimentary organic matter under geologic conditions. In this model, compositionally specific reactants evolve to specific intermediate and mobile products through balanced, nth order processes, by way of a network of sequential and parallel reactions. The chemical kinetic approach is based primarily on published observed structural transformations of naturally matured, lignin-derived, sedimentary organic matter. Assuming that Upper Cretaceous Williams Fork coal in the Piceance Basin is primarily lignin-derived, the model is calibrated for the Multi-Well Experiment(MWX) Site in this basin. This kind of approach may be applied to other selectively preserved chemical components of sedimentary organic matter.

A model for lignin alteration—part II: numerical model of natural gas generation and application to the Piceance Basin, Western Colorado

The model presented here simulates a network of parallel and sequential reactions that describe the structural and chemical transformation of lignin-derived sedimentary organic matter (SOM) and the resulting generation of mobile species from shallow burial to approximately low-volatile bituminous rank. The model is calibrated to the Upper Cretaceous Williams Fork Formation coal of the Piceance Basin at the Multi-Well Experiment (MWX) Site, assuming this coal is largely derived from lignin. The model calculates the content of functional groups on the residual molecular species, C, H, and O elemental weight percents of the residual species, and moles of residual molecular species and mobile species (including components of natural gas) through time. The model is generally more sensitive to initial molecular structure of the lignin-derived molecule and the H 2O content of the system than to initial temperature, as the former affect the fundamental reaction paths. The model is used to estimate that a total of 314 trillion cubic feet (tcf) of methane is generated by the Williams Fork coal over the basin history.

Infrared spectroscopy analysis of hemp (Cannabis sativa) after selective delignification by Bjerkandera sp. at different nitrogen levels.

Fourier-transform infrared (FT-IR) spectroscopy has been used to monitor changes in C/N-modified lignocellulosic substrates from Cannabis sativa L. in a 7-week solid-state fermentation with the white-rot fungus Bjerkandera sp. strain BOS55. The microbial transformation of hemp was considered as a pretreatment to pulping processes in paper industries. Special emphasis was paid on the N-content of the substrate, which was modified by: (i) external ammonium inputs, (ii) water extraction, and (iii) protease treatment.Selective delignification in the N-limited media was observed. The most diagnostic FT-IR spectral bands in relation to changes in the lignocellulosic substrate were those corresponding to alkyl structures (2920, 1460 cm(-1)), carboxyl groups (1720 cm(-1)), amides (1650, 1540 cm(-1)) and carbohydrate (mainly 1030 cm(-1)). Simple and multiple regression functions revealed the potential of FT-IR in accurately reflecting substrate composition features previously determined by wet chemical methods. Correspondence analysis suggests C/N-dependent degradation patterns, and discriminant analysis confirmed that the differences between N-limited, N-enriched and the original substrate were significant (P < 0.05) in terms of the intensities of five FT-IR diagnostic bands (1030, 1130, 1270, 1540 and 1650 cm(-1)).The results suggest that, in the system studied, the FT-IR spectroscopy is a reliable alternative to wet chemical analyses in the routine monitoring of the success of the biologic process since it reflects both qualitative and quantitative changes and it is very sensitive to lignin alteration and to carbohydrate and protein concentration.

Chemical Nature and Composition of Compost During Mushroom Growth

Improvement of the process of mushroom composting is of importance in order to provide an optimal growing medium needed for the mushroom. Since composting produces a food source for the mushroom, the compositional changes of mushroom compost occurring during the growth cycle of the button mushroom, Agaricus bisporus, were studied. Samples were collected during spawning, casing and the following four flushes. Samples were analyzed for their elemental composition, carbohydrates, FTIR, 13C-NMR, pyrolysis-GC/MS and tetramethylammonium hydroxide (TMAH) thermochemolysis-GC/MS. The carbohydrate analysis revealed a decrease in the total amount of about 40% of the identified monosaccharides during mushroom growth. The 13C-NMR data also confirm that polysaccharides are the main fraction degraded (or utilized by the mushrooms) during the cropping period. These findings were also confirmed by changes in the absorbance of functional groups observed in the FTIR spectra. Pyrolysis data revealed chromatographic peaks related to polysaccharides-, proteins- and lignin-derived compounds. Both pyrolysis and TMAH thermochemolysis data show degradation of lignin structures during the growth period. Lignin alteration primarily involved a preferential degradation of syringyl units and oxidation of side chains of guaiacyl moieties. This study suggests that the polysaccharide fraction of the mushroom substrate is the main organic fraction utilized during the process. In addition, alterations of lignin structures have occurred although its relative content usually increases during mushroom cropping.

Lignin Signature in Soils of Shrub Patches in Northeastern Patagonia

The objective of this research was to determine the degree of decomposition and alteration of lignin in soils of two types of shrub patches , featured by the dominant species (Prosopis alpataco and Atriplex lampa) in the northeastern Patagonian region . These species have been widely utilized in land reclamation programs mainly in west and south - central Argentina . Shrub patches of both species showed different characteristics in relation to variations in the contents of polysaccharides and lignin . There were different patterns of polysaccharides and lignin distribution in both patches and in climatic seasons . Lignin concentration changes are evidence that there is a transformation in structural units when its units (vanillyl, syringyl, and cinnamyl) lose phenolic groups during oxidation, as depth in the sampled mineral soil is increased . Polysaccharides and lignin dynamics showed a temporary variability of litter quality when the total primary production , decomposition , and mineralization were different in both types of patches . The lignin decomposition pattern under aerobic conditions involves type of litter materials in patches , influ ence of the contribution of surface and subsurface roots (above ground and below ground litter), environmental conditions , and precipitation of fragments decomposed from lignin in soil solution .

Organic matter composition and degree of humification in lignite-rich mine soils under a chronosequence of pine

In the Lusatian mining district, in the eastern part of the Federal Republic of Germany, organic matter of reclaimed mine soils consists of a mixture of lignite and recently formed soil organic matter (recent carbon). The aim of the study was to investigate the recent carbon accumulation and the degree of humification of a chronosequence of young mine soils under forest. The lignite content of the forest floor, Ai (0–5 cm) and Cv horizons (1 m depth) was determined by 14CU activity measurements and the structural composition of the organic matter was characterised by 13C CPMAS NMR spectroscopy. To obtain a characterisation of the degree of humification, the soil samples were analysed for the content of polysaccharides, proteins, lignin and lipids by wet chemical methods. 14C activity measurements indicate that at the oldest site, comparable amounts of carbon accumulated in the first few centimetres of the soil profile than in natural forest soils. 13C CPMAS NMR spectra of the organic matter in the Ai horizons of the three soil profiles were dominated by aromatic and alkyl carbon species characteristic for lignite, but indicated as well an increasing contribution of carbon species from decomposing plant litter with soil age. When the results from wet chemical analyses were normalised to the total carbon content no changes with age could be noticed. After normalisation of the amount of litter compounds to the recent carbon content, the carbon identified by plant litter compound analysis decreased with increasing depth and increasing age of the soils. After 32 years the values are comparable to those of natural forest soils. These observations were confirmed by increasing degree of lignin alteration with stand age and soil depth. The data of wet chemical analyses complement data obtained by 14C activity measurements and 13C CPMAS NMR spectroscopy and lead to the conclusion that 32 years after reforestation the degree of humification of the soil organic matter is in the same range as those of natural sites.

Lignin and carbohydrates in soils under secondary forest, alley‐cropping, and continuous farming, Thailand

AbstractThis study was designed to investigate the impact of three land‐use practices in Thailand on soil organic matter (SOM) composition. The land uses were continuous farming (till), alley‐cropping, and secondary forest. Samples, taken from the top 10 cm soil surface, were fractionated into clay‐ (&lt; 2 μm), silt‐ (2–20 μm), and sand‐sized particles (20–2000 μm) prior to analyses of C, N, lignin‐derived phenols and individual carbohydrates.As particle size increased, the C/N ratio and the concentration of lignin‐derived phenols increased, whereas the degree of lignin oxidation as well as ratios of microbially derived hexoses to plant‐derived pentoses decreased. Thus, the coarser the particle size, the less the SOM was altered by microbes. Seven years of alley‐cropping increased SOM levels only little but considerably affected SOM composition by affecting the SOM of the sand fraction. The SOM concentration in the sand fraction increased in the order continuous farming &lt; alley‐cropping &lt; secondary forest. In the same order, microbial alteration of lignin and carbohydrates of sand‐sized SOM decreased. Both the different concentrations of SOM in the sand fractions as well as its different composition contributed, therefore, to different SOM among the sites. Increasing lignin‐to‐carbohydrate ratios for bulk soils and fractions in the order continuous farming &lt; alley‐cropping &lt; secondary forest reflected such changes in SOM composition sensitively.

Soil organic matter within earthworm casts of an anecic-endogeic tropical pasture community, Colombia

Large, round-shaped surface casts derived mainly from the anecic Martiodrilus sp., family Glossoscolecidae were investigated for their structural stability and the composition of soil organic matter (SOM) associated with different particle-size separates of the casts. Lignin (CuO oxidation) and carbohydrate (acid hydrolysis) signature of SOM was carried out in addition to 13C nuclear magnetic resonance (NMR) spectroscopy. Data obtained for the casts were compared with those of the surrounding surface soil of an Oxisol under grass/legume pasture following native savanna. Earthworm casts showed significantly higher contents of large (3.15–5 and 5–8 mm) water-stable aggregates than the surrounding soil (765 g kg- 1 vs. 390 g kg −1). This higher structural stability of the casts corresponded with their higher organic C concentration (56 g C kg −1) compared with the surrounding soil (26 g C kg −1). The increase was most pronounced for organic C associated with sand-sized separates, i.e. SOM not involved in organo-mineral complexes. Signature of microbial lignin alteration and carbohydrate composition as well as 13C NMR spectroscopy revealed that organic matter (OM) associated with sand was mainly composed of slightly decomposed plant residues. Hence, higher concentrations of carbohydrates and lignin (primary resources) and lower proportions of C-substituted aromatic C and COOH (humic compounds) observed in whole casts compared with the unfractionated surrounding soil were partly due to the intense mixing of fresh litter into the mineral soil (anecic effect). Microbial products were enriched in clay-bound SOM, and humified organic compounds dominated silt-associated SOM. However, the structural chemical analyses showed that decomposition of SOM bound to silt- and clay-sized particles appeared to be in a more advanced stage in the surrounding soil than in the casts. The data provided evidence that carbohydrate-rich plant debris is responsible for structural stability of earthworm casts, besides mucopolysaccharides derived from microorganisms in the intestines of earthworms and the earthworms themselves. According to Golchin et al. (1994) it was hypothesised that microbial metabolism of notably plant-derived carbohydrates results in the release of mucilage and other metabolites which permeate the coatings of mineral particles and thus stabilise the casts. The consequence of the intimate association of slightly decomposed plant debris with the mineral phase is the build-up of a rather active but physically protected C pool which is released concurrently with the disintegration of the casts.

Lignin and carbohydrate alteration in particle-size separates of an oxisol under tropical pastures following native savanna

Establishment of improved tropical pastures on acid savanna soils of low fertility can increase the soil organic matter (SOM) content and soil fertility. Our objective was to follow the quantitative and qualitative changes of SOM associated with sand-, silt-and clay-sized separates after establishment of a grass-alone ( Brachiaria decumbens) and a grass-legume ( Brachiaria decumbens + Pueraria phaseoloides) pasture on isohyperthermic savanna soils of Colombia. Additionally, earthworm casts of anecic and endo-anecic species derived from the grass-legume pasture were investigated. Whole soil and size separates were analyzed for C, N, lignin-derived phenols (alkaline CuO-oxidation) and carbohydrates (4 m trifluoroacetic acid hydrolysis). For native savanna, grass-alone and grass-legume pasture the C content increased in the order sand (1.6–3.3 g C kg −1) < silt (25.8–32.1 g C kg −1) < clay (38.8–43.0 g C kg −1); the C-to-N ratio decreased in the same order. Fifteen years of pasture establishment resulted in an increase of C by factors of ca. 2 (sand), 1.3 (silt) and 1.1 (clay) compared to native savanna. Decreasing yields of phenolic CuO-oxidation products and increasing side-chain oxidation of the remnant lignin indicated progressive lignin alteration with decreasing particle size. Soil under savanna was substantially lower in intact lignin structures than soil under grass-alone and grass-legume pastures. Enrichment factors, E = (mg kg −1 soil under pasture/mg kg −1 soil under savanna), for lignin-derived phenolics after establishment of B. decumbens and B. decumbens + P. phaseoloides were 3.9 and 2.7, 4.3 and 2.4, and 2.6 and 2.6 in sand-, silt-and clay-sized separates, respectively. Clay-bound SOM was rich in microbially-derived sugars, whereas the SOM of the sand-sized separates contained large amounts of plant-derived sugars. Silt-associated SOM had low concentrations of both. Establishment of grass-alone and grass-legume pasture increased the amount of easily-degradable plant-derived sugars by factors of 3.0 and 3.5 (sand), 1.9 and 1.3 (silt), and 1.1 and 1.1 (clay). SOM distribution across size separates suggested an increasing amount of unprotected macro-OM after establishment of grass-alone and grass-legume pastures. Concurrently, lignin and carbohydrate signature indicated higher contents of relatively undergraded plant-derived SOM, notably in the sand-sized separates. It was concluded that the increase of this SOM fraction has beneficial effects on the soil internal N cycle as far as N mineralization and N immobilization is concerned. Earthworm casts were characterized by a tremendous enrichment of C, intact lignin and plant-derived sugars in the sand-sized separates, compared with the surrounding soil. This suggested a pronounced incorporation of fresh litter into the mineral soil (anecic effect), that decomposition processes were dramatically slowed in the casts, and a pool of relatively labile, but physically-protected SOM was built up.

Land‐use effects on the composition of organic matter in particle‐size separates of soil: I. Lignin and carbohydrate signature

SummarySoil from Eutrochrept A horizons under long‐term spruce forest (Sf), mixed deciduous forest (Df), permanent grassland (Gp) and arable rotation (Ar) was fractionated according to particle size and analysed for contents of C, N, lignin‐derived phenols and carbohydrates.Whole soil from Sf, Df, Gp and Ar contained 84, 59, 73 and 25 g C kg−1 soil, respectively. For all sites, the C content declined and C/N ratio increased in the order: clay (&lt;2 μm), silt (2–20 μm), sand (20–2000 μm). Clay and silt were significantly lower in C in Ar than in Sf, Df and Gp, C associated with sand being substantially lower under arable rotation.The yield of lignin‐derived phenols decreased and carboxyl functionality and methoxyl demethylation of lignin derivatives increased with decreasing particle size, indicating a progressive lignin alteration. Whole soil from Sf and Gp was substantially higher in vanillyl (V), syringyl (S) and cinnamyl (C) units (VSC) than soil from Df and Ar. Compared to whole soil, clay was depleted and sand enriched in VSC. Only sand appeared to be affected significantly by land use. Sand from Ar and Df was more enriched in VSC than sand from Gp and Sf.Whole soil carbohydrates decreased in the order: Gp&gt;Ar&gt;Df&gt;Sf. Sand‐ and clay‐sized separates were enriched in carbohydrates compared to silt. Carbohydrates in sand were mainly of plant origin whereas microbially‐derived sugars accounted for a larger proportion in the clay. Compared to Sf, Df and Gp, clay from Ar was enriched and sand depleted in microbial sugars.Lignin and carbohydrate distribution patterns indicate that organic matter was in a more advanced stage of decomposition in the sand separates from forest than from agricultural A horizons. The forest soils also show a higher degree of oxidative changes in lignin associated with clay. In contrast, differences between silt from the four A horizons were small.

Comparative study of fractions from alkaline extraction of wheat straw through chemical degradation, analytical pyrolysis, and spectroscopic techniques

A comparative assessment of spectroscopic and degradative techniques was carried out to characterize fractions from the sodium hydroxide extraction of wheat straw. CPMAS 13C NMR and IR spectra revealed lignin, lignin-carbohydrate complex, and hemicellulose in laboratory and industrial fractions. Preferential removal by alkali of syringyl lignin was observed, and lignin alteration during biological treatment of pulping effluents was indicated by enhanced carbonyl and alkyl signals. Relatively high syringyVguaiacy1 ratio values were obtained by cupric oxide degradation when compared with those from NMR and Py-GC-MS, the latter including ferulic acid. Additional information on straw polymer association and the role of cinnamic acids was obtained. The high guaiacyl content in lignin associated to the hemicellulose suggested bonds between the latter and guaiacyl lignin. Most linked p-coumaric acid was merely esterified, whereas ferulic acid was preferentially associated to lignin by nonsaponifiable bonds.

Lignin Alteration by Ganoderma australe and other White-Rot Fungi after Solid-State Fermentation of Beech Wood

Lignin Alteration by <i>Ganoderma australe </i>and other White-Rot Fungi after Solid-State Fermentation of Beech Wood

Humic substances distribution and transformation in forest soils

The distribution and transformation of humic substances in forest soils is investigated by CPMAS 13C NMR spectroscopy and chemical analyses. Studies on bulk soil samples and humic acid fractions indicate that different forest humus types result from different rates but similar pathways of litter decomposition. The main features of humification in the investigated forest humus profiles are preferential mineralization of carbohydrates, strong alteration of lignin leading to increasing proportions of carbon-substituted aromatic rings and loss of phenolic groups, increase in carboxyl group contents and accumulation of refractory alkyl components. The action of earthworms promotes transformation of plant residues to humic substances and incorporation of organic matter into stable organo-mineral complexes.

Chemical transformation of wheat straw constituents after solid-state fermentation with selected lignocellulose-degrading fungi

The changes in the composition of major straw constituents were studied after solid-state fermentation with ligninolytic and cellulolytic fungi in order to evaluate fungal treatments for biological upgrading of wheat straw. Species of Pleurotus and Trametes increased in vitro digestibility (attaining 60–70% of the straw dry wt) and the polysaccharide hexose/pentose ratio. Trametes versicolor caused large simultaneous degradation, but preferential removal of lignin was achieved with the Pleurotus species. The low protein content and the straw deficiency in certain amino acids was compensated by solid-state fermentation ( T. versicolor increased x 10 lysine content). Fungal alteration of lignin after the straw treatment with ligninolytic species was evidenced by non-destructive techniques and CuO alkaline degradation, the latter showing a decrease in the syringyl/guaiacyl ratio and in the cinnamic acid content.

Decomposition pattern of lignin in forest litters and soils

Abstract To characterize the degree of alteration of the lignin molecule during biodegradation, CuO oxidation has been used in litters and soils. Condensed lignin structures are not attacked by the relatively‐mild alkaline CuO oxidation, for this reason the oxidation degradation with CuO is considered a specific method for the characterization of intact lignin structures in forest litters and soils. In this paper we examine two natural lignins, one from a gymnosperm litter, the other from angiosperm litter and from respective soils under air pollution conditions. The sum of phenolic CuO oxidation products gives an overall pattern of lignin decomposition. The degree of alteration of remnant lignin is described by the acid‐to‐aldehyde ratio (AC:A1) of syringyl and vanillyl units (S:V) for angiosperm lignin. The air pollution conditions do not influenced the degree of lignin degradation.