Lignin Methoxyl Groups Research Articles

Effects of microwave-assisted drying on the drying shrinkage and chemical properties of bamboo stems

This study aimed to evaluate changes in the microwave-assisted drying shrinkage and chemical properties of a bamboo stem treated by microwave-assisted drying. The result showed that the bamboo stem treated via microwave-assisted drying exhibited a wall thickness shrinkage rate of 3.88 %，which was lower than that of natural bamboo (4.36 %). A sizable number of C-C bonds and C–O bonds were formed while the carbonyl and hydroxyl groups were reduced on the surface of the treated bamboo. This observation indicates that the treated bamboo stem showed an altered chemical bond location on the surface. Meanwhile, microwave-assisted drying partly degraded polysaccharides from hemicellulose and lignin, oxidizing the methoxyl and aromatic hydroxyl groups in lignin, and increasing the absorption peak at 148 ppm. The treated samples had a decreased amorphous region near the fiber surface and hemicellulose content and increased secondary crystalline fibers. In addition, the hydroxyl groups on the cell surface underwent a condensation reaction via microwave irradiation, and intramolecular hydroxyl groups were formed in the amorphous region, increasing the consistent arrangement of cellulose and lignin. The parenchyma cells were largely deformed, decreasing the orientation of cellulose and lignin on the cell surface, as well as reducing the absorption peak.

Measurement and research status of stable hydrogen isotopes in tree-ring lignin methoxyl groups

The primary hydrogen (H) source for all organic compounds in the biosphere is from water, and then participates in biogeochemical cycles through photosynthesis and plant physiological metabolism. As a new proxy of paleoclimate and paleoenvironment, stable hydrogen isotope ratios in wood lignin methoxyl groups (δ2HLM) show great advantages in the studies of paleoclimatic change and have been used to reconstruct precipitation stable hydrogen isotope ratios and paleoclimate signals in many regions. Based on the lignin application mechanism and analysis method of δ2HLM, we evaluated the stability and effectiveness of δ2HLM-measurement method from lignin content and lignin monomer composition, and expounded the tree lignin methoxyl groups' stable isotope proxies of current research outcomes. In the middle latitudes, the tree-ring δ2HLM had great potential in recording temperature signals and precipitation stable hydrogen isotope ratios. However, the study of tree-ring δ2HLM was still in its infancy as evidenced by following reasons: 1) The study area was limited to the middle latitude of the northern hemisphere, and the study subjects were limited to conifer species; 2) To compensate for the limitation of hydrogen isotopic records of nitrocellulose, high resolution tree-ring δ2HLM would be studied; 3) The potential of tree-ring δ2HLM utilization in plant physiology and forest ecology remained to be exploited.

Temperature signal recorded in δ2H and δ13C values of wood lignin methoxyl groups from a permafrost forest in northeastern China

Stable isotopes in wood lignin methoxyl groups (δ2HLM and δ13CLM values) have been suggested as valuable complementary paleoclimate proxies. In permafrost forests, tree growth is influenced by multiple factors, however temperature appears to have the strongest impact on tree growth and, therefore, on carbon cycling. To test whether δ2HLM and δ13CLM values of trees from permafrost regions might record climate parameters, two dominant tree species (Larix gmelinii, larch, and Pinus sylvestris var. mongolica, pine) collected from a permafrost forest in China's Greater Hinggan Mountains, were investigated. The two tree species larch and pine covered time spans of 1940 to 2013 and 1870 to 2013, respectively. Results showed significant correlations of pine and larch δ2HLM values and larch δ13CLM values with temperatures and in particular with the mean temperature of the growing season from April to August. However, only weak correlations of δ2HLM and δ13CLM values with moisture conditions, such as precipitation amount and relative humidity were observed. In addition, species specificity in the climate response was most obvious for δ13CLM values. Compared to a temperature reconstruction based on tree ring width, pine δ2HLM–based reconstruction showed strongest spatial correlations with regional temperature. Therefore, δ2HLM values might be a promising proxy to reconstruct growing-season temperatures in permafrost regions.

Tree-ring δ2H values from lignin methoxyl groups indicate sensitivity to European-scale temperature changes

Stable hydrogen isotope ratios of lignin methoxyl groups (δ2HLM) of wood have been shown to reflect climate-sensitive δ2H values of precipitation (δ2Hprecip). However, a detailed calibration study between high-resolution δ2HLM and δ2Hprecip data has not been performed yet. Here, we present annually resolved δ2HLM values from nine tree-ring series (derived from four Fagus sylvatica L. trees) collected near a station of the Global Isotope Network of Isotopes in Precipitation (GNIP) and the meteorological observatory at Hohenpeißenberg (Germany; ~48°N, 11°E). The nine δ2HLM tree-ring series show highly significant inter-series correlations (Rbar = 0.52) over the common period of overlap 1916–2015 and no sign of a major juvenile trend affecting the first decades of growth. When compared with local instrumental data, the combined δ2HLM chronology is most indicative for annually averaged δ2Hprecip values. In line with this finding, the δ2HLM chronology shows similar climatic imprints as commonly observed for European stable water isotopes. We find the highest correlation (r = 0.72, p < 0.001) with temperature changes averaged over large-scale areas (range: 15°W–20°E, 25–75°N) including marine and continental Western Europe. This large-scale temperature signal is not entirely stable over time, but weakens from 1948 to 1982 where 31-year running correlations drop systematically. The temporal signal strength coincides with a decline in Rbar values but also with known anomalous atmospheric circulation events (e.g., winter of 1956). We conclude two main findings. First, the temporal robustness of the transfer model is mainly controlled by the internal coherency among the tree-ring δ2HLM series. An improved understanding of such temporal discrepancies among the proxy data may therefore optimize reconstruction models. Second, this study highlights the need to critically assess the impact of changing atmospheric circulation patterns on the relationship between climate parameters and stable water isotopes.

The Study of Water Sorption with Hydrolysis Lignin by Solid-State NMR Spectroscopy

Hydrolysis lignin is formed as a by-product of cellulose production and has limited industrial application. The ability of hydrolysis lignin to absorb and retain some water is important aspect for the study of its properties and modification methods. The processes of water sorption by hydrolysis lignin were studied with solid-state NMR spectroscopy. The samples were humidified in desiccators containing different saturated salts solutions with different relative air humidity above them. The sorption capacity of the samples was determined by water sorbed from the air, and it was found that lignin absorbs the amount of water equal to 40% of sample weight at maximum relative humidity of the air. The cross-polarization (CP) and magic angle spinning (MAS) methods were used to register solid-state NMR spectra. Using the 1H-NMR spectra, it was found that the hydrolysis lignin is hydrated in the whole volume, and the water penetrates into the deep layers of polymer, however, the distribution of water at the likely sorption sites is uneven. It was obtained with use of 13C-NMR spectroscopy that hydrolysis lignin hydrates in both hydrophilic and hydrophobic regions of the macromolecule, and the bulk of sorbed water (~64%) concentrates around the hydroxyl and methoxyl groups of lignin and polysaccharide residues.

Earliest Eocene cold period and polar amplification - Insights from δ2H values of lignin methoxyl groups of mummified wood

Three well-preserved mummified wood specimens have been excavated from three earliest Eocene (~55.5, 55.2 and 53.3 Ma) kimberlite pipes in the subarctic Northwest Territories, Canada (~64°N). Each specimen contained multi-decadal length tree-ring series and allowed measurements of stable hydrogen isotope ratios (δ2H values) of the lignin methoxyl groups (commonly used cellulose was largely degraded). We used these δ2H signatures for the reconstruction of three representative δ2H values of the local precipitation by applying calibrated isotope fractionations to investigate deep-time paleoclimatology. Our reconstructions indicate unprecedented low values for the subarctic early Eocene which, however, show within ~2.2 Myr an increasing trend from −206 ± 17, −202 ± 17 to −168 ± 17‰. These values were interpreted along with other Arctic, subarctic and mid-latitudinal proxy records of that time period indicating in total a period of low stable hydrogen and oxygen isotope ratios in precipitation (onset between ~55.7 and 54.9 Ma and a recovery at 53.3 ± 0.6 Ma) which is assumed to have been primarily caused by a continental cold period. An increased magnitude of this cold period was noted for our subarctic reconstructions pointing to a polar amplification where surface air temperature changes in the Arctic exceed the global trend (in response to climate forcing). In an attempt to quantify the polar amplification magnitude we estimated Arctic temperature changes using our δ2H results in combination with existing relationships between early Eocene temperatures and stable water isotopes. Comparing the Arctic temperature change with a global estimation proposes a polar amplification of magnitude <4. Our estimate for the earliest Eocene shows either agreement or indicates a lower magnitude when compared to previously described Cenozoic polar amplifications commonly ranging between 2 and 4.

Warm season precipitation signal in δ2 H values of wood lignin methoxyl groups from high elevation larch trees in Switzerland.

In this study, we tested stable hydrogen isotope ratios of wood lignin methoxyl groups (δ2 Hmethoxyl values) as a palaeoclimate proxy in dendrochronology. This is a quite new method in the field of dendrochronology and the sample preparation is much simpler than the methods used before to measure δ2 H values from wood. We measured δ2 Hmethoxyl values in high elevation larch trees (Larix decidua Mill.) from Simplon Valley (southern Switzerland). Thirty-seven larch trees were sampled and five individuals analysed for their δ2 Hmethoxyl values at annual (1971-2009) and pentadal resolution (1746-2009). The δ2 Hmethoxyl values were measured as CH3 I released upon treatment of the dried wood samples with hydroiodic acid. 10-90 μL from the head-space were injected into the gas chromatography/high-temperature conversion/isotope ratio mass spectrometry (GC/HTC-IRMS) system. Testing the climate response of the δ2 Hmethoxyl values, the annually resolved series show a positive correlation of r = 0.60 with June/July precipitation. The pentadally resolved δ2 Hmethoxyl series do not show any significant correlation to climate parameters. Increased precipitation during June and July, which are on average warm and relatively dry months, results in higher δ2 H values of the xylem water and, therefore, higher δ2 H values in the lignin methoxyl groups. Therefore, we suggest that δ2 Hmethoxyl values of high elevation larch trees might serve as a summer precipitation proxy.

A fast track for the accurate determination of methoxyl and ethoxyl groups in lignin

Robust and fast quantification of methoxyl and ethoxyl groups in all types of lignin.

Stable hydrogen isotope values of lignin methoxyl groups of four tree species across Germany and their implication for temperature reconstruction.

Stable hydrogen isotope ratios of lignin methoxyl groups (δ2HLM values) in wood have been shown to mirror the δ2H signatures of precipitation (δ2Hprecip values). Thus, δ2HLM values were suggested to serve as a potential paleotemperature proxy since δ2Hprecip values are dominantly controlled by air temperature in the mid-latitudes. A recent study where a significant δ2HLM-temperature relationship was found for a European transect with mean annual temperatures ranging from -4 to 17°C strengthened this assumption. However, using δ2HLM values as a paleotemperature proxy requires quantification of noise from site-, species- and biosynthetic-specific influences to determine the significance of recording smaller temperature changes. Here, we measured δ2HLM values of tree-ring sections covering 1981-1990 and 1991-2011 of four different tree species (European beech, English oak, Scots pine, Norway spruce) at 15 sampling sites across Germany. The maximum difference in mean annual temperature between sample sites was 5°C and all sites showed small temperature increases from 1981 to 1990 to 1991-2011 (mean Δ=0.7°C). For all species investigated, the maximum difference of δ2HLM within the tree was <10mUr or ‰ (median values) and between trees at a single site was ≤28mUr (median values). The general pattern of the spatial δ2HLM-temperature relationship found for the European transect was confirmed here although a significant correlation was lacking. This can be explained by the lower spatial δ2Hprecip-temperature correlation (R2=0.39) found for sampling sites in this study and the δ2HLM differences between trees. Nevertheless, the temporal changes in δ2HLM values of European beech trees correctly reflected within ±2°C the temperature change at every sampling site. Therefore, we suggest that δ2HLM values of European beech trees have considerable potential for reconstructing temperature changes when applied on tree-ring chronologies and consider this approach particularly suited for Late Holocene climate studies.

Mean annual temperatures of mid-latitude regions derived from δ2H values of wood lignin methoxyl groups and its implications for paleoclimate studies

Tree-rings are widely used climate archives providing annual resolutions on centennial to millennial timescales. Stable isotope ratios of tree-rings have been applied to assist with the delineation of climate parameters such as temperature and precipitation. Here, we investigated stable hydrogen isotope ratios (expressed as δ2H values) of lignin methoxyl groups of wood from various tree species collected along a ~3500km north-south transect across Europe with mean annual temperatures (MAT) ranging from −4 to +17°C. We found a strong linear relationship between MATs and δ2H values of wood lignin methoxyl groups. We used this relationship to predict MATs from randomly collected wood samples and found general agreement between predicted and observed MATs for the mid-latitudes on a global scale. Our results are discussed in context of their paleoclimate relevance and suggest that δ2H values of lignin methoxyl groups might have the potential to reconstruct MATs when applied on mid-latitudinal tree-ring chronologies of the Late Holocene.

Climate signals in δ13C of wood lignin methoxyl groups from high-elevation larch trees

In this study, a barely used method to measure δ13C values from lignin methoxyl groups (δ13Cmethoxyl) of tree‐rings is applied to high alpine larch trees to test their potential as a climate proxy. Thirty-seven larch trees (Larix decidua Mill.) were sampled at a tree line site near Simplon Village in the Valais/Switzerland. Samples were used to measure tree-ring width, and from five individuals, δ13Cmethoxyl was determined at annual resolution from 1971 to 2009, and at pentadal resolution from 1747 to 2009.The physiological tree responses to increasing atmospheric CO2 concentration since 1850 and the corresponding decrease in δ13C (Suess effect) were corrected using a range of published discrimination factors and approaches. One of these approaches considers a flexible correction factor, which minimizes the residuals with target climate data.Testing the response of the new δ13Cmethoxyl proxy to climate revealed significant correlations with June to August temperatures, ranging from r=0.56 to 0.75 for annually and from r=0.41 to 0.87 for pentadally resolved data depending on the correction methods. Tree-ring width also shows significant correlations with June to August temperature. These results demonstrate the potential of δ13Cmethoxyl to serve as a summer temperature proxy in high-elevation alpine environments.

δ2H, δ13C and δ18O from whole wood, α-cellulose and lignin methoxyl groups in Pinus sylvestris: a multi-parameter approach

Novel tree ring parameters – δ13C and δ2H from methoxyl groups – have been developed to reconstruct palaeoclimate. Tests with δ13C and δ18O derived from whole wood and cellulose samples, however, indicated differences in the isotopic composition and climate signal, depending on the extracted wood component. We assess this signal dependency by analysing (i) δ13C and δ18O from whole wood and cellulose and (ii) δ13C and δ2H from methoxyl groups, using Pinus sylvestris L. growing near Altenkirchen (Germany). Results indicate significant correlations among the time series derived from whole wood, cellulose, and lignin methoxyl groups. Compared with the whole wood samples, δ13C from methoxyl groups showed a different and overall lower response to climate parameters. On the other hand, δ2H from methoxyl groups showed high correlations with temperature and was also correlated with ring width, indicating its potential as a temperature proxy. Isotope time series with the highest correlation with climatic parameter were: (i) whole wood and cellulose δ13C with growing season precipitation and summer temperature; (ii) methoxyl groups with spring precipitation; (iii) whole wood and cellulose δ18O correlates with annual evapotranspiration and water balance; and (iv) methoxyl group δ2H with spring temperatures. These findings reveal that multiple climate elements can be reconstructed from different wood components and that whole wood proxies perform comparably to cellulose time series.

Precipitation of lignin from softwood black liquor: An investigation of the equilibrium and molecular properties of lignin

Extracting lignin from black liquor is an attractive option in modern pulp mills as a unit process for a combined biorefinery. The lignin obtained can be utilized as solid fuel or other high-value added products. The precipitation equilibrium of kraft lignin from softwood black liquor was studied in this work. It was found that with decreasing pH and temperature, or increasing ion strength, the solid yield increases. Moreover, precipitated softwood kraft lignin has a higher molecular weight and contains lower amounts of carbohydrates and phenolic groups than lignin precipitated from mixed hardwood/softwood black liquor. The content of methoxyl groups in softwood kraft lignin was found to decrease with increasing precipitation yield. An empirical model for estimating the precipitation yield of lignin was proposed and evaluated.

Precipitation of Lignin from Softwood Black Liquor: An Investigation of the Equilibrium and Molecular Properties of Lignin

Extracting lignin from black liquor is an attractive option in modern pulp mills as a unit process for a combined biorefinery. The lignin obtained can be utilized as solid fuel or other high-value added products. The precipitation equilibrium of kraft lignin from softwood black liquor was studied in this work. It was found that with decreasing pH and temperature, or increasing ion strength, the solid yield increases. Moreover, precipitated softwood kraft lignin has a higher molecular weight and contains lower amounts of carbohydrates and phenolic groups than lignin precipitated from mixed hardwood/softwood black liquor. The content of methoxyl groups in softwood kraft lignin was found to decrease with increasing precipitation yield. An empirical model for estimating the precipitation yield of lignin was proposed and evaluated.

D/H ratios of methoxyl groups of the sedimentary organic matter of Lake Holzmaar (Eifel, Germany): A potential palaeoclimate/-hydrology proxy

Stable hydrogen isotope ratios (δD values) of methoxyl groups in lignin and pectin from a variety of plant types from different locations have been shown to mirror δD values of precipitation, with a mean uniform isotopic fractionation. Since δD in precipitation is mainly influenced by climatic conditions, including temperature, evaporation and precipitation amount, methoxyl groups of organic matter have been proposed as a potential palaeoclimate proxy. Here, we measured the δD values of the methoxyl groups of sedimentary organic matter derived from sediment core segments of Lake Holzmaar (Eifel, Germany). The sediment core covers the entire Holocene and part of the Late Glacial (until 13,650years BP). Since the sedimentary organic matter was indicated by organic source proxies of predominantly phytoplanktonic origin, we considered the δD values of the methoxyl groups as a proxy for the δD value of the lake water. Presently and probably during most of the Holocene, the δD value of precipitation was primarily controlled by temperature (2–4.5‰/°C) as well as in isotopic equilibrium with the δD value of the lake water. We used these modern temperature sensitivities of the Eifel region together with the measured δD values of the methoxyl groups of the sedimentary organic matter to evaluate temperature changes recorded for the Holocene. The resulting mean temperature variance was found to be consistently less than 1.8–4°C and is broadly in line with that reported from the NGRIP ice core for the same period. The transition from the Holocene to the Late Glacial period was accompanied with more negative δD values of the methoxyl groups (∼13‰ for the Younger Dryas). Besides the association with temperature we assumed a higher susceptibility of the δD value of Lake Holzmaar to evaporative enrichment during the Younger Dryas which could serve as an explanation for discrepancies reported for existing palaeoclimate/-hydrology records of the Eifel region. Our findings indicate that the δD values of methoxyl groups have great potential for assisting with palaeoclimate and palaeohydrology, particularly when the organic matter is well characterized and of uniform origin.

Lignin methoxyl hydrogen isotope ratios in a coastal ecosystem

Stable hydrogen isotope ratios of plant lignin methoxyl groups have recently been shown to record the hydrogen isotopic composition of meteoric water. Here we extend this technique towards tracing water source variations across a saltwater to freshwater gradient in a coastal, subtropical forest ecosystem. We measure the hydrogen isotopic composition of xylem water (δDxw) and methoxyl hydrogen (δDmethoxyl) to calculate fractionations for coastal mangrove, buttonwood and hammock tree species in Sugarloaf Key, as well as buttonwoods from Miami, both in Florida, USA. Prior studies of the isotopic composition of cellulose and plant leaf waxes in coastal ecosystems have yielded only a weak correlation to source waters, attributed to leaf water effects. Here we find δDmethoxyl values range from −230‰ to −130‰, across a 40‰ range in δDxw with a regression equation of δDmethoxyl ‰=1.8*δDxw−178‰ (R2=0.48, p<0.0001, n=74). This is comparable within error to the earlier published relationship for terrestrial trees which was defined across a much larger 125‰ isotopic range in precipitation. Analytical precision for measurements of δD values of pure CH3I by gas chromatography–pyrolysis–isotope ratio mass spectrometry (GC–P–IRMS) is σ=6‰ (n=31), which is considerably better than for CH3I liberated through cleavage with HI from lignin with σ=18‰ (n=26). Our results establish that δDmethoxyl can record water sources and salinity incursion in coastal ecosystems, where variations sufficiently exceed method uncertainties (i.e., applications with δD excursions >50‰). For the first time, we also report yields of propyl iodide, which may indicate lignin synthesis of propoxyl groups under salt-stress.

Carbon, hydrogen and oxygen stable isotope ratios of whole wood, cellulose and lignin methoxyl groups of Picea abies as climate proxies

Carbon, hydrogen and oxygen (C, H and O) stable isotope ratios of whole wood and components are commonly used as paleoclimate proxies. In this work we consider eight different proxies in order to discover the most suitable wood component and stable isotope ratio to provide the strongest climate signal in Picea abies in a southeastern Alpine region (Trentino, Italy). δ(13)C, δ(18)O and δ(2)H values in whole wood and cellulose, and δ(13)C and δ(2)H values in lignin methoxyl groups were measured. Analysis was performed using an Isotopic Ratio Mass Spectrometer coupled with an Elemental Analyser for measuring (13)C/(12)C and a Pyrolyser for measuring (2)H/(1)H and (18)O/(16)O. The data were evaluated by Principal Component Analysis, and a simple Pearson's correlation between isotope chronologies and climatic features, and multiple linear regression were performed to evaluate the data. Each stable isotope ratio in cellulose and lignin methoxyl differs significantly from the same stable isotope ratio in whole wood, the values begin higher in cellulose and lignin except for the lignin δ(2)H values. Significant correlations were found between the whole wood and the cellulose fractions for each isotope ratio. Overall, the highest correlations with temperature were found with the δ(18)O and δ(2)H values in whole wood, whereas no significant correlations were found between isotope proxies and precipitation. δ(18)O and δ(2)H values in whole wood provide the best temperature signals in Picea abies in the northern Italian study area. Extraction of cellulose and lignin and analysis of other isotopic ratios do not seem to be necessary.

Stable isotope determination of ester and ether methyl moieties in plant methoxyl groups

Plant methoxyl groups of lignin and pectin have both distinct stable hydrogen isotope (δ2H) and carbon isotope (δ13C) values that can be used for studying environmental processes and for investigating the origin and authenticity of biomaterials. Up to now, the reported methods have been applied only to determine isotope values of the bulk plant methoxyl pool. In this work, we have applied several methods to distinguish between stable isotope ratios of methoxyl groups of pectin and the bulk plant methoxyl pool. Our results demonstrate that by applying alkaline hydrolysis to specifically cleave off the ester methyl moiety (pectin-like), we can distinguish δ2H and δ13C values of the pectin methoxyl pool from the bulk methoxyl pool. No measureable isotope discrimination was observed either during sample preparation or during analytical measurement. Furthermore, using this method, no major isotope difference in either the hydrogen or carbon isotope signature of the methoxyl groups of plant pectin and bulk matter from plant species such as leaves from trees, apples, carrots and potatoes was noted. We show the methanol released during alkaline hydrolysis of plant material and subsequently treated with hydriodic acid to be an excellent procedure to measure specifically and precisely the δ13C and δ2H isotope values of plant pectin-like methoxyl groups. This method is particularly advantageous when plant matter with a low methoxyl content has to be analysed.

Biosorption of Cr(VI) by coconut coir: Spectroscopic investigation on the reaction mechanism of Cr(VI) with lignocellulosic material

In this study, the removal mechanism of Cr(VI) from water by coconut coir (CC) was investigated using X-ray photoelectron spectroscopy (XPS), Cr K-edge X-ray absorption near edge structure (XANES) and FTIR spectroscopy. The results showed that, upon reaction with CC at pH 3, Cr(VI) was reduced to Cr(III), which was either bound to CC or released back into solution. As revealed by the FTIR spectra of CC before and after reacting with Cr(VI), the phenolic methoxyl and hydroxyl groups of lignin in CC are the dominant drivers of Cr(VI) reduction, giving rise to carbonyl and carboxyl groups on CC. These functional groups can subsequently provide binding sites for Cr(III) resulting from Cr(VI) reduction. In conjunction with forming complexes with carbonyl and carboxyl groups, the formation of Cr(III) hydroxide precipitate could also readily occur as revealed by the linear combination fitting of the Cr K-edge XANES spectrum using a set of reference compounds. The phenolic groups in lignin are responsible for initiating Cr(VI) reduction, so lignocellulosic materials containing a higher amount of phenolic groups are expected to be more effective scavengers for removal of Cr(VI) from the environment.

Methoxyl groups of lignin are essential carbon donors in C1 metabolism of Sphingobium sp. SYK‐6

Sphingobium sp. SYK-6 can utilize lignin biphenyl compounds, such as 2,2'-dihydroxy-3,3'-dimethoxy-5,5'-dicarboxybiphenyl (DDVA). In the metabolism of DDVA, this microorganism exploits two O -demethylation systems with different substrate specificities, namely, a DDVA-specific oxygenative O -demethylation system and a vanillate-specific (VA-specific) tetrahydrofolate-dependent (THF-dependent) methyltransferase system. We examined the way in which these two systems interact in the metabolism of lignin in Sphingobium sp. SYK-6. Our results indicate that THF accepts methyl groups derived not only from the THF-dependent O -demethylation of VA but also from the oxygenative O -demethylation of DDVA. Thus, the methoxyl groups of lignin model compounds are an essential source of carbon in Sphingobium sp. SYK-6. ((c) 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim).