Preparation of specifically labeled C-(lignin)- and C-(cellulose)-lignocelluloses and their decomposition by the microflora of soil

Microbial decomposition of lignocellulose in soil was studied using radioisotope techniques. Natural lignocelluloses containing C in either their lignin or cellulose (glucan) components were prepared by feeding plants l-[U-C]phenylalanine or d-[U-C]glucose, respectively, through their cut stems. Detailed chemical and chromatographic characterization of labeled lignocelluloses from three hardwood and three softwood species showed that those labeled by the [C]glucose incorporation method contained specifically labeled cellulosic components, whereas those labeled by the [C]phenylalanine incorporation method contained specifically labeled lignin components. Microbial degradation of these differentially labeled lignocelluloses was followed by monitoring CO(2) evolution from selected soil samples incubated with known amounts of radiolabeled lignocelluloses. The lignin components of the six woods were shown to be decomposed in soil 4 to 10 times more slowly than their cellulosic components. These rates of mineralization were comparable to the generalized patterns previously reported in the literature. The present technique, however, was thought to be simpler, more sensitive, and less prone to interference than methods previously available.     

Lignocellulose decomposition by selected streptomyces strains

From 30 actinomycete cultures isolated by enrichment technique on agar media containing newsprint as a primary carbon and energy source, three Streptomyces strains were selected for characterization of their lignocellulose-decomposing abilities. All three streptomycetes were capable of oxidizing specifically 14C-labeled lignocelluloses to 14CO2. These Streptomyces were shown to attack primarily the cellulosic (glucan) components, of which between 25 to 40% evolved as 14CO2 during 1,025 h of incubation depending upon the culture used. Lignin labeled lignocelluloses were also attacked, but to a lesser degree, with up to about 3.5% being oxidized to 14CO2 depending upon the culture used. Additionally, it was shown that purified 14C-labeled milled-wood lignin was attacked, with recoveries of up to 17.7% of the label was 14CO2. This is the first conclusive evidence to show that streptomycetes can decompose lignin.     

Lignocellulose decomposition by selected streptomyces strains.

From 30 actinomycete cultures isolated by enrichment technique on agar media containing newsprint as a primary carbon and energy source, three Streptomyces strains were selected for characterization of their lignocellulose-decomposing abilities. All three streptomycetes were capable of oxidizing specifically 14C-labeled lignocelluloses to 14CO2. These Streptomyces were shown to attack primarily the cellulosic (glucan) components, of which between 25 to 40% evolved as 14CO2 during 1,025 h of incubation depending upon the culture used. Lignin labeled lignocelluloses were also attacked, but to a lesser degree, with up to about 3.5% being oxidized to 14CO2 depending upon the culture used. Additionally, it was shown that purified 14C-labeled milled-wood lignin was attacked, with recoveries of up to 17.7% of the label was 14CO2. This is the first conclusive evidence to show that streptomycetes can decompose lignin.     

Preparation, characterization, and microbial degradation of specifically radiolabeled [C]lignocelluloses from marine and freshwater macrophytes

Specifically radiolabeled [C-lignin]lignocelluloses were prepared from the aquatic macrophytes Spartina alterniflora, Juncus roemerianus, Rhizophora mangle, and Carex walteriana by using [C]phenylalanine, [C]tyrosine, and [C]cinnamic acid as precursors. Specifically radiolabeled [C-polysaccharide]lignocelluloses were prepared by using [C]glucose as precursor. The rates of microbial degradation varied among [C-lignin]lignocelluloses labeled with different lignin precursors within the same plant species. To determine the causes of these differential rates, [C-lignin]lignocelluloses were thoroughly characterized for the distribution of radioactivity in nonlignin contaminants and within the lignin macromolecule. In herbaceous plants, significant amounts (8 to 24%) of radioactivity from [C]phenylalanine and [C]tyrosine were found associated with protein, although very little (3%) radioactivity from [C]cinnamic acid was associated with protein. Microbial degradation of radiolabeled protein resulted in overestimation of lignin degradation rates in lignocelluloses derived from herbaceous aquatic plants. Other differences in degradation rates among [C-lignin]lignocelluloses from the same plant species were attributable to differences in the amount of label being associated with ester-linked subunits of peripheral lignin. After acid hydrolysis of [C-polysaccharide]lignocelluloses, radioactivity was detected in several sugars, although most of the radioactivity was distributed between glucose and xylose. After 576 h of incubation with salt marsh sediments, 38% of the polysaccharide component and between 6 and 16% of the lignin component (depending on the precursor) of J. roemerianus lignocellulose was mineralized to CO(2); during the same incubation period, 30% of the polysaccharide component and between 12 and 18% of the lignin component of S. alterniflora lignocellulose was mineralized.     

Decomposition of [C]Lignocelluloses of Spartina alterniflora and a Comparison with Field Experiments

Decomposition of lignocelluloses from Spartina alterniflora in salt-marsh sediments was measured by using C-labeled compounds. Rates of decomposition were fastest in the first 4 days of incubation and declined later. Lignins labeled in side chains were mineralized slightly faster than uniformly labeled lignins; 12% of the [side chain-C]lignin-labeled lignocellulose was mineralized after 816 h of incubation, whereas only 8% of the [U-C]lignin-labeled lignocelluloses were degraded during this period. The carbohydrate moiety within the lignocellulose complex was degraded about four times faster than the lignin moiety; after 816 h of incubation, 29 to 37% of the carbohydrate moiety had been mineralized. Changes in concentration of lignin and cellulose in litter of S. alterniflora were followed over 2 years of decay. Cellulose disappeared from litter more rapidly than lignin; 50% of the initial content of cellulose was lost after 130 days, whereas lignin required 330 to 380 days for 50% loss. The slow loss of lignin compared with other litter components resulted in a progressive enrichment of litter in lignin content. The rates of mineralization of [C]lignocelluloses in marsh sediments were similar to the rates of lignocellulose decomposition in litter on the marsh.     

Lignin-solubilizing ability of actinomycetes isolated from termite (Termitidae) gut.

The lignocellulose-degrading abilities of 11 novel actinomycete strains isolated from termite gut were determined and compared with that of the well-characterized actinomycete, Streptomyces viridosporus T7A. Lignocellulose bioconversion was followed by (i) monitoring the degradation of [14C]lignin- and [14C]cellulose-labeled phloem of Abies concolor to 14CO2 and 14C-labeled water-soluble products, (ii) determining lignocellulose, lignin, and carbohydrate losses resulting from growth on a lignocellulose substrate prepared from corn stalks (Zea mays), and (iii) quantifying production of a water-soluble lignin degradation intermediate (acid-precipitable polymeric lignin). The actinomycetes were all Streptomyces strains and could be placed into three groups, including a group of five strains that appear superior to S. viridosporus T7A in lignocellulose-degrading ability, three strains of approximately equal ability, and three strains of lesser ability. Strain A2 was clearly the superior and most effective lignocellulose decomposer of those tested. Of the assays used, total lignocellulose weight loss was most useful in determining overall bioconversion ability but not in identifying the best lignin-solubilizing strains. A screening procedure based on 14CO2 evolution from [14C-lignin]lignocellulose combined with measurement of acid-precipitable polymeric lignin yield was the most effective in identifying lignin-solubilizing strains. For the termite gut strains, the pH of the medium showed no increase after 3 weeks of growth on lignocellulose. This is markedly different from the pattern observed with S. viridosporus T7A, which raises the medium pH considerably. Production of extracellular peroxidases by the 11 strains and S. viridosporus T7A was followed for 5 days in liquid cultures.(ABSTRACT TRUNCATED AT 250 WORDS)     

Lignin-solubilizing ability of actinomycetes isolated from termite (Termitidae) gut

The lignocellulose-degrading abilities of 11 novel actinomycete strains isolated from termite gut were determined and compared with that of the well-characterized actinomycete, Streptomyces viridosporus T7A. Lignocellulose bioconversion was followed by (i) monitoring the degradation of [14C]lignin- and [14C]cellulose-labeled phloem of Abies concolor to 14CO2 and 14C-labeled water-soluble products, (ii) determining lignocellulose, lignin, and carbohydrate losses resulting from growth on a lignocellulose substrate prepared from corn stalks (Zea mays), and (iii) quantifying production of a water-soluble lignin degradation intermediate (acid-precipitable polymeric lignin). The actinomycetes were all Streptomyces strains and could be placed into three groups, including a group of five strains that appear superior to S. viridosporus T7A in lignocellulose-degrading ability, three strains of approximately equal ability, and three strains of lesser ability. Strain A2 was clearly the superior and most effective lignocellulose decomposer of those tested. Of the assays used, total lignocellulose weight loss was most useful in determining overall bioconversion ability but not in identifying the best lignin-solubilizing strains. A screening procedure based on 14CO2 evolution from [14C-lignin]lignocellulose combined with measurement of acid-precipitable polymeric lignin yield was the most effective in identifying lignin-solubilizing strains. For the termite gut strains, the pH of the medium showed no increase after 3 weeks of growth on lignocellulose. This is markedly different from the pattern observed with S. viridosporus T7A, which raises the medium pH considerably. Production of extracellular peroxidases by the 11 strains and S. viridosporus T7A was followed for 5 days in liquid cultures.(ABSTRACT TRUNCATED AT 250 WORDS)     

Decomposition of [14C]Lignocelluloses of Spartina alterniflora and a Comparison with Field Experiments

Decomposition of lignocelluloses from Spartina alterniflora in salt-marsh sediments was measured by using ¹⁴C-labeled compounds. Rates of decomposition were fastest in the first 4 days of incubation and declined later. Lignins labeled in side chains were mineralized slightly faster than uniformly labeled lignins; 12% of the [side chain-¹⁴C]lignin-labeled lignocellulose was mineralized after 816 h of incubation, whereas only 8% of the [U-¹⁴C]lignin-labeled lignocelluloses were degraded during this period. The carbohydrate moiety within the lignocellulose complex was degraded about four times faster than the lignin moiety; after 816 h of incubation, 29 to 37% of the carbohydrate moiety had been mineralized. Changes in concentration of lignin and cellulose in litter of S. alterniflora were followed over 2 years of decay. Cellulose disappeared from litter more rapidly than lignin; 50% of the initial content of cellulose was lost after 130 days, whereas lignin required 330 to 380 days for 50% loss. The slow loss of lignin compared with other litter components resulted in a progressive enrichment of litter in lignin content. The rates of mineralization of [¹⁴C]lignocelluloses in marsh sediments were similar to the rates of lignocellulose decomposition in litter on the marsh.     

Preparation, Characterization, and Microbial Degradation of Specifically Radiolabeled [14C]Lignocelluloses from Marine and Freshwater Macrophytes

Specifically radiolabeled [¹⁴C-lignin]lignocelluloses were prepared from the aquatic macrophytes Spartina alterniflora, Juncus roemerianus, Rhizophora mangle, and Carex walteriana by using [¹⁴C]phenylalanine, [¹⁴C]tyrosine, and [¹⁴C]cinnamic acid as precursors. Specifically radiolabeled [¹⁴C-polysaccharide]lignocelluloses were prepared by using [¹⁴C]glucose as precursor. The rates of microbial degradation varied among [¹⁴C-lignin]lignocelluloses labeled with different lignin precursors within the same plant species. To determine the causes of these differential rates, [¹⁴C-lignin]lignocelluloses were thoroughly characterized for the distribution of radioactivity in nonlignin contaminants and within the lignin macromolecule. In herbaceous plants, significant amounts (8 to 24%) of radioactivity from [¹⁴C]phenylalanine and [¹⁴C]tyrosine were found associated with protein, although very little (3%) radioactivity from [¹⁴C]cinnamic acid was associated with protein. Microbial degradation of radiolabeled protein resulted in overestimation of lignin degradation rates in lignocelluloses derived from herbaceous aquatic plants. Other differences in degradation rates among [¹⁴C-lignin]lignocelluloses from the same plant species were attributable to differences in the amount of label being associated with ester-linked subunits of peripheral lignin. After acid hydrolysis of [¹⁴C-polysaccharide]lignocelluloses, radioactivity was detected in several sugars, although most of the radioactivity was distributed between glucose and xylose. After 576 h of incubation with salt marsh sediments, 38% of the polysaccharide component and between 6 and 16% of the lignin component (depending on the precursor) of J. roemerianus lignocellulose was mineralized to ¹⁴CO₂; during the same incubation period, 30% of the polysaccharide component and between 12 and 18% of the lignin component of S. alterniflora lignocellulose was mineralized.     

14C-labeled substrate catabolism by human diploid fibroblasts derived from infants and adults

Untransformed diploid skin fibroblasts from eight normal adults, aged 24 to 74 years, catabolized several 14C-labeled substrates less effectively than cells from ten normal male infants. 14C-labeled substrate metabolism was quantitated either by measuring the evolution of 14CO2 from the 14C-labeled compounds or the incorporation of 14C into cellular protein via transamination of tricarboxylic acid cycle intermediates derived from the 14C-labeled substrates. With these methods, adult cells catabolized [1-14C]butyrate, [1-14C]octanoate, and 1-[2-14C]leucine at rates 44 to 64% of those found in infant cells. The oxidation of [1,4-14C]succinate and [U-14C]malate was identical in both infant and adult cells, while [2,3-14C]succinate catabolism was mildly decreased in adult cells (65-80% of control). These observations parallel those made in rat tissues and confirm that the same phenomenon occurs in cultured human fibroblasts.     

Degradation of softwood [14C lignin] lignocelluloses and its relation to the formation of humic substances in river and pond environments

The fate of lignin in water and sediment of the Garonne river (France) and of a pond in its floodplain was examined using specifically labeled [¹⁴C-lignin] lignocelluloses. No significant differences appeared in the mineralization rate of alder, poplar or willow [¹⁴C-lignin] in running water samples. Conversion of total radioactivity to ¹⁴CO₂ ranged between 18.7% and 24.4% after 120 days of incubation. Degree of ¹⁴C-labeled lignin mineralization in standing water and sediments was clearly lower, especially in submerged sediments, and was correlated with oxygen supply. After 60 days of incubation 3.3% to 7.9% of the ¹⁴C-labeled lignin was recovered in water samples as dissolved organic carbon originating from microbial metabolism. In water extracts from sediment the percentage of dissolved organic ¹⁴C was only 0.4% to 1.3% of the applied activity. In the humic fraction extracted from sediments it did not exceed 4.4% which was much lower than in soils. No significant difference appeared between river and pond conditions for humic substances formation.     

Absence of microbial mineralization of lignin in anaerobic enrichment cultures.

The existence of anaerobic biodegradation of lignin was examined in mixed microflora. Egyptian soil samples, in which rapid mineralization of organic matter takes place in the presence of an important anaerobic microflora, were used to obtain the anaerobic enrichment cultures for this study. Specifically, 14CO2 or [14C]lignin wood was used to investigate the release of labeled gaseous or soluble degradation products of lignin in microbial cultures. No conversion of 14C-labeled lignin to 14CO2 or 14CH4 was observed after 6 months of incubation at 30 degrees C in anaerobic conditions with or without NO3-. A small increase in soluble radioactivity was observed in certain cultures, but it could not be related to the release of catabolic products during the anaerobic biodegradation of lignin.     

Absence of microbial mineralization of lignin in anaerobic enrichment cultures

The existence of anaerobic biodegradation of lignin was examined in mixed microflora. Egyptian soil samples, in which rapid mineralization of organic matter takes place in the presence of an important anaerobic microflora, were used to obtain the anaerobic enrichment cultures for this study. Specifically, 14CO2 or [14C]lignin wood was used to investigate the release of labeled gaseous or soluble degradation products of lignin in microbial cultures. No conversion of 14C-labeled lignin to 14CO2 or 14CH4 was observed after 6 months of incubation at 30 degrees C in anaerobic conditions with or without NO3-. A small increase in soluble radioactivity was observed in certain cultures, but it could not be related to the release of catabolic products during the anaerobic biodegradation of lignin.     

Anaerobic Biodegradation of the Lignin and Polysaccharide Components of Lignocellulose and Synthetic Lignin by Sediment Microflora

Specifically radiolabeled [¹⁴C-lignin]lignocelluloses and [¹⁴C-polysaccharide]lignocelluloses were prepared from a variety of marine and freshwater wetland plants including a grass, a sedge, a rush, and a hardwood. These [¹⁴C]lignocellulose preparations and synthetic [¹⁴C]lignin were incubated anaerobically with anoxic sediments collected from a salt marsh, a freshwater marsh, and a mangrove swamp. During long-term incubations lasting up to 300 days, the lignin and polysaccharide components of the lignocelluloses were slowly degraded anaerobically to ¹⁴CO₂ and ¹⁴CH₄. Lignocelluloses derived from herbaceous plants were degraded more rapidly than lignocellulose derived from the hardwood. After 294 days, 16.9% of the lignin component and 30.0% of the polysaccharide component of lignocellulose derived from the grass used (Spartina alterniflora) were degraded to gaseous end products. In contrast, after 246 days, only 1.5% of the lignin component and 4.1% of the polysaccharide component of lignocellulose derived from the hardwood used (Rhizophora mangle) were degraded to gaseous end products. Synthetic [¹⁴C]lignin was degraded anaerobically faster than the lignin component of the hardwood lignocellulose; after 276 days, 3.7% of the synthetic lignin was degraded to gaseous end products. Contrary to previous reports, these results demonstrate that lignin and lignified plant tissues are biodegradable in the absence of oxygen. Although lignocelluloses are recalcitrant to anaerobic biodegradation, rates of degradation measured in aquatic sediments are significant and have important implications for the biospheric cycling of carbon from these abundant biopolymers.     

Metabolism of Radiolabeled beta-Guaiacyl Ether-Linked Lignin Dimeric Compounds by Phanerochaete chrysosporium

Phanerochaete chrysosporium metabolized the radiolabeled lignin model compounds [gamma-C]guaiacylglycerol-beta-guaiacyl ether and [4-methoxy-C]veratrylglycerol-beta-guaiacyl ether (VI) to CO(2) in stationary and in shaking cultures. CO(2) evolution was greater in stationary culture. CO(2) evolution from [gamma-C]guaiacyl-glycerol-beta-guaiacyl ether and [4-methoxy-C]veratrylglycerol-beta-guaiacyl ether in stationary cultures was two- to threefold greater when 100% O(2) rather than air (21% O(2)) was the gas phase above the cultures. CO(2) evolution from the metabolism of the substrates occurred only as the culture entered the stationary phase of growth. The presence of substrate levels of nitrogen in the medium suppressed CO(2) evolution from both substrates in stationary cultures. [C]veratryl alcohol and 4-ethoxy-3-methoxybenzyl alcohol were formed as products of the metabolism of VI and 4-ethoxy-3-methoxyphenylglycerol-beta-guaiacyl ether, respectively.     

Functional differences in the catabolism of branched-chain L-amino acids in cultured normal and maple syrup urine disease fibroblasts

Possible functional differences in the catabolism of the four branched-chain L-amino acids in maple syrup urine disease were assessed using cultured human skin fibroblast stains. Transamination and oxidative decarboxylation were comparatively studied in 90-min incubations with 1 mmole/liter of 1-14C-labeled substrates. In normal cell strains (n = 5), apparent transamination rates (sum of branched-chain 2-oxo[14C]acid and 14CO2 release; means expressed in nmole/90 min/mg of cell protein) were in the order L-leucine (32) greater than L-valine (17) greater than or equal to L-isoleucine (14) greater than L-allo-isoleucine (8); 14CO2 production was in the order L-valine (9) greater than L-isoleucine (6) greater than or equal to L-leucine (5) greater than L-allo-isoleucine (2). In variant (n = 5) as well as classical (n = 2) MSUD cell lines, branched-chain 2-oxo-[14C]acid release rates were generally comparable to the control values. As compared to the 14CO2 release in controls (= 100%), branched-chain 2-oxo acid dehydrogenase activity in MSUD fibroblasts was individually reduced and varied considerably between strains (residual activity 2-38%). Within individual strains, only small differences in the residual decarboxylation activity were observed in incubations with L-valine, L-leucine, and L-isoleucine. It was remarkably high, however, when L-allo-isoleucine was applied as a substrate. With the exception of L-allo-isoleucine, apparent total transamination rates of branched-chain L-amino acids were therefore distinctly lower in MSUD cells than in normal cells.     

Use of field-based stable isotope probing to identify adapted populations and track carbon flow through a phenol-degrading soil microbial community

The goal of this field study was to provide insight into three distinct populations of microorganisms involved in in situ metabolism of phenol. Our approach measured 13CO2 respired from [13C]phenol and stable isotope probing (SIP) of soil DNA at an agricultural field site. Traditionally, SIP-based investigations have been subject to the uncertainties posed by carbon cross-feeding. By altering our field-based, substrate-dosing methodologies, experiments were designed to look beyond primary degraders to detect trophically related populations in the food chain. Using gas chromatography-mass spectrometry (GC/MS), it was shown that (13)C-labeled biomass, derived from primary phenol degraders in soil, was a suitable growth substrate for other members of the soil microbial community. Next, three dosing regimes were designed to examine active members of the microbial community involved in phenol metabolism in situ: (i) 1 dose of [13C]phenol, (ii) 11 daily doses of unlabeled phenol followed by 1 dose of [13C]phenol, and (iii) 12 daily doses of [13C]phenol. GC/MS analysis demonstrated that prior exposure to phenol boosted 13CO2 evolution by a factor of 10. Furthermore, imaging of 13C-treated soil using secondary ion mass spectrometry (SIMS) verified that individual bacteria incorporated 13C into their biomass. PCR amplification and 16S rRNA gene sequencing of 13C-labeled soil DNA from the 3 dosing regimes revealed three distinct clone libraries: (i) unenriched, primary phenol degraders were most diverse, consisting of alpha-, beta-, and gamma-proteobacteria and high-G+C-content gram-positive bacteria, (ii) enriched primary phenol degraders were dominated by members of the genera Kocuria and Staphylococcus, and (iii) trophically related (carbon cross-feeders) were dominated by members of the genus Pseudomonas. These data show that SIP has the potential to document population shifts caused by substrate preexposure and to follow the flow of carbon through terrestrial microbial food chains.     

Study of lignin biotransformation by Aspergillus fumigatus and white-rot fungi using (14)C-labeled and unlabeled kraft lignins

The biodegradation of lignin by fungi was studied in shake flasks using (14)C-labeled kraft lignin and in a deep-tank fermentor using unlabeled kraft lignin. Among the fungi screened, A. fumigatus-isolated in our laboratories-was most potent in lignin biotransformation. Dialysis-type fermentation, designed to study possible accumulation of low MW lignin-derived products, showed no such accumulation. Recalcitrant carbohydrates like mi-crocrystalline cellulose supported higher lignolytic activity than easily metabolized carbohydrates like cellobiose. An assay developed to distinguish between CO(2) evolved from lignin and carbohydrate substrates demonstrated no stoichiometric correlation between the metabolism of the two cosubstrates. The submerged fermentations with unlabeled lignin are difficult to monitor since chemical assays do not give accurate and true results. Lignolytic efficiencies that allowed monitoring of such fermentations were defined. Degraded lignins were analyzed for structural modifications. A. fumigatus was clearly superior to C. versicolor in all aspects of lignin degradation; A. fumigatus brought about substantial demethoxylation and dehydroxylation, whereas C. versicolor degraded lignins closely resembled undegraded kraft lignin. There was a good agreement among the different indices of lignin degradation, namely, (14)CO evolution, OCH(3) loss, OH loss, and monomer and dimer yield after permanganate oxidation.     

Hexose metabolism in pancreatic islets: unequal oxidation of the two carbons of glucose-derived acetyl residues.

The fate of the C1 and C2 of glucose-derived acetyl residues was examined in rat pancreatic islets. The production of 14CO2 from D-[2-14C]glucose exceeded that from D-[6-14C]glucose, in the same manner as the oxidation of [1-14C]acetate exceeded that of [2-14C]acetate. The difference in 14CO2 output from D-[2-14C]glucose and D-[6-14C]glucose was matched by complementary differences in the generation of 14C-labeled acidic metabolites and amino acids. Even the production of 14C-labeled L-lactate was somewhat higher in the case of D-[6-14C]glucose than D-[2-14C]glucose. The ratio between D-[2-14C]glucose and D-[6-14C]glucose oxidation progressively decreased at increasing concentrations of the hexose (2.8, 7.0, and 16.7 mM), was higher after 30 than 120 min incubation, and was decreased in the presence of a nonmetabolized analogue of L-leucine. These findings are consistent with the view that the difference between D-[6-14C]glucose and D-[2-14C]glucose oxidation is mainly attributable to the inflow into the Krebs cycle of unlabeled metabolites generated from endogenous nutrients, this being compensated by the exit of partially labeled metabolites from the same cycle. The present results also indicate that the oxidation of glucose-derived acetyl residues relative to their generation in the reaction catalyzed by pyruvate dehydrogenase is higher than that estimated from the ratio between D-[6-14C]glucose and D-[3,4-14C]glucose conversion to 14CO2.     

New insights into the ligninolytic capability of a wood decay ascomycete

Wood-grown cultures of Daldinia concentrica oxidized a permethylated beta-(14)C-labeled synthetic lignin to (14)CO(2) and also cleaved a permethylated alpha-(13)C-labeled synthetic lignin to give C(alpha)-C(beta) cleavage products that were detected by (13)C nuclear magnetic resonance spectrometry. Therefore, this ascomycete resembles white-rot basidiomycetes in attacking the recalcitrant nonphenolic structures that predominate in lignin.