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PubMedDate not supplied

Optimal experimental condition for hemicellulosic hydrolyzate treatment with activated charcoal for xylitol production.

Rice straw was hydrolyzed into a mixture of sugars using diluted H(2)SO(4). During hydrolysis, a variety of inhibitors was also produced, including acetic acid, furfural, hydroxymethylfurfural, and lignin degradation products (several aromatic and phenolic compounds). To reduce the toxic compounds concentration in the hydrolyzate and to improve the xylitol yield and volumetric productivity, rice straw hemicellulosic hydrolyzate was treated with activated charcoal under different pH values, stirring rates, contact times, and temperatures, employing a 2(4) full-factorial design. Fermentative assays were conducted with treated hydrolyzates containing 90 g/L xylose. The results indicated that temperature, pH, and stirring rate strongly influenced the hydrolyzate treatment, temperature and pH interfering with all of the responses analyzed (removal of color and lignin degradation products, xylitol yield factor, and volumetric productivity). The combination of pH 2.0, 150 rpm, 45 degrees C, and 60 min was considered an optimal condition, providing significant removal rates of color (48.9%) and lignin degradation products (25.8%), as well as a xylitol production of 66 g/L, a volumetric productivity of 0.57 g/L.h, and a yield factor of 0.72 g/g.

Adsorption↗
PubMed2002

Role of inorganic chlorides in formation of PCDDs, PCDFs, and coplanar PCBs from combustion of plastics, newspaper, and pulp in an incinerator.

The total amounts of dioxins found in exhaust gases from combustion of polyethylene (PE), polystyrene (PS), and poly(ethylene terephthalate) (PET) with approximately 3% (w/ w) NaCl were 6.07, 17.7, and 28.9 ng/g, respectively. Plastics containing benzene rings produced more dioxins than plastic containing no benzene ring. The amounts of dioxin formed in the exhaust gases from the combustion of newspapers impregnated with CaCl2, KCl, and NaCl were 18.6, 28.6, and 49.0 ng/g, respectively. Dioxin formation was associated with the bond energy between metal atom and chlorine atom. When newspapers impregnated with four different amounts of NaCl were combusted, the highest NaCl content newspaper (chlorine content 4.08%, w/w; lignin content 19.8%, w/w) produced the greatest amount of dioxins (174 ng/g). Pulp with NaCl (chlorine content 4.25%, w/w; lignin content 0.69%, w/w) produced more dioxins (6.71 ng/g) than pulp alone (0.799 ng/g) did upon combustion. The lignin content in a combustion sample correlated with the amount of dioxin formation. The results exhibited that combustion conditions with low CO concentration (<2 ppm) produced much less dioxins than conditions with high CO concentration (159 ppm).

Air Pollutants↗
PubMed1999

Enzyme-catalyzed saccharification of model celluloses in the presence of lignacious residues.

Experiments were designed to determine the relevance of enzyme partitioning, between the cellulose and non-cellulose components of pretreated biomass, with respect to rates of cellulose saccharification in a typical biomass-to-ethanol process. The experimental system included three cellulose preparations (differing in physicochemical properties): a representative lignin-rich noncellulosic residue (prepared from dilute acid-pretreated switchgrass), an acid-extracted lignin preparation, and a complete Trichoderma reesei cellulase preparation. Enzyme-reactor conditions were typical of those commonly used in biomass-to-ethanol studies. The results were found to be dependent on both the lignin and cellulose preparations used. The noncellulosic lignacious residue, when supplemented at up to 40% (w/w) in cellulose-cellulase reaction mixtures, had little effect on rates and extents of cellulose saccharification. Overall, the results suggest that enzyme partitioning between cellulose and the noncellulosic component of a pretreated feedstock is not likely to have a major impact on cellulose saccharification in typical biomass-to-ethanol processes.

Carbohydrate Metabolism↗
PubMed1999

cDNA cloning and heterologous expression of coniferin beta-glucosidase.

Coniferin beta-glucosidase (CBG) catalyzes the hydrolysis of monolignol glucosides to release the cinnamyl alcohols for oxidative polymerization to lignin. Utilizing the N-terminal amino acid sequence of the purified enzyme, the corresponding full-length cDNA sequence was isolated from a Pinus contorta xylem-specific library. The isolated 1909 nucleotide cDNA was confirmed to be that of CBG on the basis of its high homology to family 1 glycosyl hydrolases, the sequence identity with the N-terminal amino acid residues of the purified enzyme, and the coniferin hydrolytic activity and substrate specificity profile displayed by the recombinant protein when expressed in Escherichia coli. The presence of a 23 amino acid N-terminal signal peptide in the deduced 513 amino acid enzyme suggests that CBG is a secretory protein targeted to the ER. The isolation of CBG cDNA will facilitate the evaluation of the importance of this enzyme in the ultimate stages of lignin biosynthesis and could be a valuable tool in manipulating lignin levels in xylem cell walls.

Amino Acid Sequence↗
PubMed2002

Characterization of the Saccharomyces cerevisiae YMR318C (ADH6) gene product as a broad specificity NADPH-dependent alcohol dehydrogenase: relevance in aldehyde reduction.

YMR318C represents an open reading frame from Saccharomyces cerevisiae with unknown function. It possesses a conserved sequence motif, the zinc-containing alcohol dehydrogenase (ADH) signature, specific to the medium-chain zinc-containing ADHs. In the present study, the YMR318C gene product has been purified to homogeneity from overexpressing yeast cells, and found to be a homodimeric ADH, composed of 40 kDa subunits and with a pI of 5.0-5.4. The enzyme was strictly specific for NADPH and was active with a wide variety of substrates, including aliphatic (linear and branched-chain) and aromatic primary alcohols and aldehydes. Aldehydes were processed with a 50-fold higher catalytic efficiency than that for the corresponding alcohols. The highest k(cat)/K(m) values were found with pentanal>veratraldehyde > hexanal > 3-methylbutanal >cinnamaldehyde. Taking into consideration the substrate specificity and sequence characteristics of the YMR318C gene product, we have proposed this gene to be called ADH6. The disruption of ADH6 was not lethal for the yeast under laboratory conditions. Although S. cerevisiae is considered a non lignin-degrading organism, the catalytic activity of ADHVI can direct veratraldehyde and anisaldehyde, arising from the oxidation of lignocellulose by fungal lignin peroxidases, to the lignin biodegradation pathway. ADHVI is the only S. cerevisiae enzyme able to significantly reduce veratraldehyde in vivo, and its overexpression allowed yeast to grow under toxic concentrations of this aldehyde. The enzyme may also be involved in the synthesis of fusel alcohols. To our knowledge this is the first NADPH-dependent medium-chain ADH to be characterized in S. cerevisiae.

Alcohol Dehydrogenase↗
PubMed1993

Influence of cellobiose oxidase on peroxidases from Phanerochaete chrysosporium.

Reduction of H2O2-oxidized manganese peroxidase (MnP), lignin peroxidase and, to some extent, horseradish peroxidase, was studied in the presence of cellobiose oxidase (CbO) and cellobiose. It was found that the reversion rates for MnP compound II and lignin peroxidase compound II back to native enzymes increased significantly in the presence of CbO and cellobiose. However, the reduction of cytochrome c by CbO plus cellobiose was 40 times faster than the reduction of MnP compound II. Also, the lag phase before reversion to the native states decreased for all three peroxidases in the presence of CbO and cellobiose. Active CbO did not repress formation of compounds I or II of the peroxidases, and Mn2+/veratryl alcohol reduced compound II of the peroxidases much more rapidly than did active CbO. This indicates that, in the presence of Mn2+ or veratryl alcohol, MnP and lignin peroxidase can complete their catalytic cycles and function normally without interference from CbO. Without the presence of peroxidase substrates, active CbO reduced compound II of the above peroxidases.

Basidiomycota↗
PubMed2003

Non-degradative dissolution and acetylation of ball-milled plant cell walls: high-resolution solution-state NMR.

Two solvent systems for fully dissolving, and optionally derivatizing, finely ground plant cell wall material at room temperature are described: dimethylsulfoxide (DMSO) and tetrabutylammonium fluoride (TBAF) or N-methylimidazole (NMI). In situ acetylation produces acetylated cell walls (Ac-CWs) that are fully soluble in chloroform. Lignin structures tested remain fully intact. The dispersion of 13C-1H correlations afforded by two-dimensional (2D) nuclear magnetic resonance (NMR) experiments reveals the major lignin units, allowing the whole lignin fraction to be analyzed by high-resolution solution-state NMR methods for the first time. Non-degradative cell wall dissolution offers the potential to analyze polysaccharide components, and improve current cell wall analytical methods by using standard homogeneous solution-state chemistry.

Acetylation↗
PubMed1986

Substrate free radicals are intermediates in ligninase catalysis.

The H2O2-requiring ligninase of the basidiomycete Phanerochaete chrysosporium oxidatively cleaves both lignin and lignin model compounds between C alpha and C beta (C-1 and C-2) of their aliphatic side chains. Previous work has demonstrated a reaction mechanism by which ligninase oxidizes aromatic substrates to their cation radicals, which then undergo side chain cleavage to yield carbon-centered free radicals. These carbon-centered radicals add O2 to give substrate peroxyl radicals that react further to yield the hydroxylated and carbonylated end products usually seen in experiments with ligninase. To investigate this radical mechanism, we have now designed three dimeric lignin models: 1-(3,4-dimethoxyphenyl)-2-phenylethanol (I), 1-(3,4-dimethoxyphenyl)-2-phenylpropanol (II), and 1-(3,4-dimethoxyphenyl)-2-methyl-2-phenylpropanol (III). The following results were obtained when these models were oxidized by ligninase: methyl groups at C beta of the substrate favored C alpha-C beta cleavage versus C alpha oxidation to the ketone. GC/MS and HPLC analysis showed that II gave a radical coupling dimer, 2,3-diphenylbutane, as a major (26% yield) reaction product under anaerobic conditions. The anaerobic oxidation of III yielded 2,3-dimethyl-2,3-diphenylbutane. Spin-trapping experiments with nitrosobenzene showed that model II oxidation produced alpha-methylbenzyl radicals, whereas model III oxidation gave alpha, alpha-dimethylbenzyl radicals. TLC and iodometric determinations showed that III gave cumene hydroperoxide as a major (21% yield) reaction product in air. These findings demonstrate that carbon-centered and peroxyl radicals at C beta are major products of C alpha-C beta cleavage by ligninase.

Basidiomycota↗
PubMed1998

Compartmentalized expression of two structurally and functionally distinct 4-coumarate:CoA ligase genes in aspen (Populus tremuloides).

4-Coumarate:CoA ligases (4CLs, EC 6.2.1.12) are a group of enzymes necessary for maintaining a continuous metabolic flux for the biosynthesis of plant phenylpropanoids, such as lignin and flavonoids, that are essential to the survival of plants. So far, various biochemical and molecular studies of plant 4CLs seem to suggest that 4CL isoforms in plants are functionally indistinguishable in mediating the biosynthesis of these phenolics. However, we have discovered two functionally and structurally distinct 4CL genes, Pt4CL1 and Pt4CL2 (63% protein sequence identity), that are differentially expressed in aspen (Populus tremuloides). The Escherichia coli-expressed and purified Pt4CL1 and Pt4CL2 proteins exhibited highly divergent substrate preference as well as specificity that reveal the association of Pt4CL1 with the biosynthesis of guaiacyl-syringyl lignin and the involvement of Pt4CL2 with other phenylpropanoid formation. Northern hybridization analysis demonstrated that Pt4CL1 mRNA is specifically expressed in lignifying xylem tissues and Pt4CL2 mRNA is specifically expressed in epidermal layers in the stem and the leaf, consistent with the promoter activities of Pt4CL1 and Pt4CL2 genes based on the heterologous promoter-beta-glucouronidase fusion analysis. Thus, the expression of Pt4CL1 and Pt4CL2 genes is compartmentalized to regulate the differential formation of phenylpropanoids that confer different physiological functions in aspen; Pt4CL1 is devoted to lignin biosynthesis in developing xylem tissues, whereas Pt4CL2 is involved in the biosynthesis of other phenolics, such as flavonoids, in epidermal cells.

Amino Acid Sequence↗
PubMed1986

The role of condensed tannins in the nutritional value of Lotus pedunculatus for sheep. 4. Sites of carbohydrate and protein digestion as influenced by dietary reactive tannin concentration.

1. Vegetative secondary growth Lotus pedunculatus was cut daily, and fed fresh at hourly intervals (600 g dry matter (DM)/d) to three groups each of three sheep fitted with permanent cannulas into the rumen and duodenum. Lotus fed to two of the groups was sprayed with low and high rates of polyethylene glycol (PEG; molecular weight 3350), which specifically binds the condensed tannins (CT). Nutrient intake and faecal excretion were measured directly, duodenal flows estimated from continuous intraruminal infusion of inert ruthenium phenanthroline (Ru-P) and CrEDTA markers, and rumen pool sizes measured at slaughter. 2. Dietary concentrations of total reactive CT (i.e. that not bound to PEG) were 95, 45 and 14 g/kg DM, whilst the corresponding values for free CT were 15, 5 and 2 g/kg DM. 3. Increasing dietary reactive CT concentration linearly increased duodenal flows of non-ammonia nitrogen, but linearly decreased the apparent digestibility of energy and organic matter, and rumen digestion of hemicellulose but not of cellulose. Rumen digestion as a proportion of total digestion was increased by the higher PEG rate for organic matter, energy, pectin and lignin. 4. High dietary CT concentration was associated with increased N retention. Rumen ammonia concentration and pool size showed only a slight decline on this diet, indicating that there must have been increased recycling of N into the rumen. 5. Increasing dietary reactive CT concentration had no effect on the rate at which carbohydrate constituents were degraded in the rumen per unit time (FDR), but increased the rate at which their undegraded residues (FOR) left the rumen per unit time. The latter appeared to be the principal mechanism by which rumen digestion as a proportion of total digestion was reduced at high dietary CT concentrations. From a comparison of FDR and FOR of carbohydrate components in lotus and Brassica oleracea diets, it was concluded that hemicellulose digestion was rate-limiting for rumen cell-wall digestion, probably due to bonding with lignin. However, the considerable post-rumen digestion of hemicellulose was not associated with post-rumen lignin digestion. 6. It was concluded that a desired concentration of CT in Lotus sp. should represent a balance between the positive effect of CT in improving the efficiency of N digestion and their negative effect in depressing rumen carbohydrate digestion. A recommended concentration is 30-40 g/kg DM.

Animals↗
PubMed2003

Consequences of plant phenolic compounds for productivity and health of ruminants.

Plant phenolic compounds are diverse in structure but are characterised by hydroxylated aromatic rings (e.g. flavan-3-ols). They are categorised as secondary metabolites, and their function in plants is often poorly understood. Many plant phenolic compounds are polymerised into larger molecules such as the proanthocyanidins (PA; condensed tannins) and lignins. Only the lignins, PA, oestrogenic compounds and hydrolysable tannins will be considered here. Lignins slow the physical and microbial degradation of ingested feed, because of resilient covalent bonding with hemicellulose and cellulose, rather than any direct effects on the rumen per se. The PA are prevalent in browse and are expressed in the foliage of some legumes (e.g. Lotus spp.), but rarely in grasses. They reduce the nutritive value of poor-quality diets, but can also have substantial benefits for ruminant productivity and health when improved temperate forages are fed. Beneficial effects are dependent on the chemical and physical structure, and concentration of the PA in the diet, but they have been shown to improve live-weight gain, milk yield and protein concentration, and ovulation rate. They prevent bloat in cattle, reduce gastrointestinal nematode numbers, flystrike and CH4 production. Some phenolic compounds (e.g. coumestans) cause temporary infertility, whilst those produced by Fusarium fungi found in pasture, silage or stored grains can cause permanent infertility. The HT may be toxic because products of their metabolism can cause liver damage and other metabolic disorders.

Animal Feed↗
PubMed1988

Dietary fiber content of selected foods.

Dietary fiber measurements are essential to assessment of the potential therapeutic and preventive effects of fiber intake. Ideally, dietary fiber analyses should measure all components--soluble polysaccharides, noncellulosic polysaccharides, cellulose, and lignin--and the constituent sugars of the soluble and noncellulosic polysaccharides. We modified existing techniques to measure reproducibly the total dietary fiber, polysaccharide, and lignin components and the sugar constituents of selected foods. Soluble-fiber content as percentage of total dietary fiber for groups of foods averaged 32% for cereal products, 32% for vegetables, 25% for dried beans, and 38% for fruits. Lignin content, estimated gravimetrically, was approximately 1.4 g/100 g dry wt for 24 foods. Detailed fiber measurements are critical for evaluating the potential health benefits of dietary fiber intake.

Bread↗
PubMed1990

Dietary and hormonal evaluation of men at different risks for prostate cancer: fiber intake, excretion, and composition, with in vitro evidence for an association between steroid hormones and specific fiber components.

Dietary fiber intake and fecal fiber excretion were investigated in 53 Seventh-day Adventist men: 18 nonvegetarians (NVs), 20 lactoovovegetarians (LOVs), and 15 vegans (Vs). Three-day composite diets and stools were analyzed for neutral detergent fiber (NDF), hemicellulose, cellulose, lignin, and pectin. In vitro binding of estrone (E1), estradiol-17 beta (E2), and testosterone (T) to a water-insoluble fiber fraction obtained from these diets was correlated with the intake of specific dietary fiber components. Vs consumed and excreted significantly more of all fiber components than did LOVs or NVs. LOVs consumed more of all fiber components (except cellulose) than did omnivores and excreted more NDF, hemicellulose, and cellulose. Dietary lignin was positively correlated with T binding in the V group. There were significant relationships for all groups combined between lignin and water-insoluble fiber binding of E1, E2, and T. Further study is needed to clarify relationships between fiber components, steroid-hormone metabolism, and risk of prostate cancer.

Adult↗
PubMed1986

Carbon-nitrogen interactions in CO(2)-enriched white oak: physiological and long-term perspectives.

The responses of forest trees to atmospheric CO(2) enrichment will depend in part on carbon-nutrient linkages. Insights into the possible long-term ecological consequences of CO(2) enrichment can be gained from studying physiological responses in short-term experiments. One-year-old white oak (Quercus alba L.) seedlings were grown in unfertilized forest soil for 40 weeks in controlled-environment chambers with ambient (362 microl l(-1)) or elevated (690 microl l(-1)) CO(2). As previously reported, seedling dry weight was 85% greater in the elevated CO(2) environment, despite severe nitrogen deficiency in all seedlings. The increase in growth occurred without a concomitant increase in nitrogen uptake, indicating an increase in nitrogen-use efficiency in elevated CO(2). The weight of new buds was greater in elevated CO(2), suggesting that shoot growth in the next year would have been enhanced relative to that of seedlings in ambient CO(2). However, there was less translocatable nitrogen in perennial woody tissue in elevated CO(2); thus, further increases in nitrogen-use efficiency may not be possible. The leaves that abscised from seedlings in elevated CO(2) contained higher amounts of soluble sugars and tannin and a lower amount of lignin compared with amounts in abscised leaves in ambient CO(2). Based on lignin:N and lignin:P ratios, the rates of litter decomposition might not be greatly affected by CO() enrichment, but the total amount of nitrogen returned to soil would be lower in elevated CO(2).

Journal Article↗
PubMed1998

Suppression of O-methyltransferase gene by homologous sense transgene in quaking aspen causes red-brown wood phenotypes

Homologous sense suppression of a gene encoding lignin pathway caffeic acid O-methyltransferase (CAOMT) in the xylem of quaking aspen (Populus tremuloides Michx.) resulted in transgenic plants exhibiting novel phenotypes with either mottled or complete red-brown coloration in their woody stems. These phenotypes appeared in all independent transgenic lines regenerated with a sense CAOMT construct but were absent from all plants produced with antisense CAOMT. The CAOMT sense transgene expression was undetectable, and the endogenous CAOMT transcript levels and enzyme activity were reduced in the xylem of some transgenic lines. In contrast, the sense transgene conferred overexpression of CAOMT and significant CAOMT activity in all of the transgenic plants' leaves and sclerenchyma, where normally the expression of the endogenous CAOMT gene is negligible. Thus, our results support the notion that the occurrence of sense cosuppression depends on the degree of sequence homology and endogene expression. Furthermore, the suppression of CAOMT in the xylem resulted in the incorporation of a higher amount of coniferyl aldehyde residues into the lignin in the wood of the sense plants. Characterization of the lignins isolated from these transgenic plants revealed that a high amount of coniferyl aldehyde is the origin of the red-brown coloration-a phenotype correlated with CAOMT-deficient maize (Zea mays L.) brown-midrib mutants.

Journal Article↗
PubMed1998

Comparison of the ability of partially N-acetylated chitosans and chitooligosaccharides to elicit resistance reactions in wheat leaves

Chitin, a linear polysaccharide composed of (1-->4)-linked 2-acetamido-2-deoxy-beta-D-glucopyranose (GlcNAc) residues, and chitosan, the fully or partially N-acetylated, water-soluble derivative of chitin composed of (1-->4)-linked GlcNAc and 2-amino-2-deoxy-beta-D-glucopyranose (GlcN), have been proposed as elicitors of defense reactions in higher plants. We tested and compared the ability of purified (1-->4)-linked oligomers of GlcNAc (tetramer to decamer) and of GlcN (pentamer and heptamer) and partially N-acetylated chitosans with degrees of acetylation (DA) of 1%, 15%, 35%, 49%, and 60% and average degrees of polymerization between 540 and 1100 to elicit phenylalanine ammonia-lyase (PAL) and peroxidase (POD) activities, lignin deposition, and microscopically and macroscopically visible necroses when injected into the intercellular spaces of healthy, nonwounded wheat (Triticum aestivum L.) leaves. Purified oligomers of (1-->4)-linked GlcN were not active as elicitors, whereas purified oligomers of (1-->4)-linked GlcNAc with a degree of polymerization >/= 7 strongly elicited POD activities but not PAL activities. Partially N-acetylated, polymeric chitosans elicited both PAL and POD activities, and maximum elicitation was observed with chitosans of intermediate DAs. All chitosans but not the chitin oligomers induced the deposition of lignin, the appearance of necrotic cells exhibiting yellow autofluorescence under ultraviolet light, and macroscopically visible necroses; those with intermediate DAs were most active. These results suggest that different mechanisms are involved in the elicitation of POD activities by GlcNAc oligomers, and of PAL and POD activities by partially N-acetylated chitosan polymers and that both enzymes have to be activated for lignin biosynthesis and ensuing necrosis to occur.

Journal Article↗
PubMed1997

Collapsed xylem phenotype of Arabidopsis identifies mutants deficient in cellulose deposition in the secondary cell wall.

Recessive mutations at three loci cause the collapse of mature xylem cells in inflorescence stems of Arabidopsis. These irregular xylem (irx) mutations were identified by screening plants from a mutagenized population by microscopic examination of stem sections. The xylem cell defect was associated with an up to eightfold reduction in the total amount of cellulose in mature inflorescence stems. The amounts of cell wall-associated phenolics and polysaccharides were unaffected by the mutations. Examination of the cell walls by using electron microscopy demonstrated that the decreases in cellulose content of irx lines resulted in an alteration of the spatial organization of cell wall material. This suggests that a normal pattern of cellulose deposition may be required for assembly of lignin or polysaccharides. The reduced cellulose content of the stems also resulted in a decrease in stiffness of the stem material. This is consistent with the irregular xylem phenotype and suggests that the walls of irx plants are not resistant to compressive forces. Because lignin was implicated previously as a major factor in resistance to compressive forces, these results suggest either that cellulose has a direct role in providing resistance to compressive forces or that it is required for the development of normal lignin structure. The irx plants had a slight reduction in growth rate and stature but were otherwise normal in appearance. The mutations should be useful in facilitating the identification of factors that control the synthesis and deposition of cellulose and other cell wall components.

Arabidopsis↗
PubMed1992

A comparison of the catalytic properties of cellobiose:quinone oxidoreductase and cellobiose oxidase from Phanerochaete chrysosporium.

Several catalytic properties of the FAD enzyme cellobiose:quinone oxidoreductase (CBQ) and the heme/FAD enzyme, cellobiose oxidase (CBO) have been investigated and compared. Dichlorophenol-indophenol was found to be a very good electron acceptor for cellobiose oxidation by both enzymes. The optimal pH value for this oxidation with dichlorophenol-indophenol as a co-substrate was observed around pH 4 for both enzymes. The turnover numbers of this reaction were also very similar. The Km values for cellobiose oxidation were identical, whereas the Km for CBO with dichlorophenol-indophenol is lower than that of CBQ. Atmospheric oxygen is a very poor electron acceptor for both CBO and CBQ, however, CBO can utilize cytochrome c as an effective electron acceptor, while CBQ cannot. The specific activity of CBO for cytochrome c is thus about 200-times higher than for oxygen. Thus, one way to distinguish the two enzymes is by the cytochrome-c-reducing ability of CBO. Therefore, we propose that the nomenclature for CBO is tentatively changed to cellobiose:cytochrome c oxidoreductase until a rational name can be installed. Both enzymes have radical-reducing activities. The cation radical, derived from 1,2,4,5-tetramethoxybenzene, was reduced by both enzymes at almost the same reaction rate. The phenoxyradical produced by lignin peroxidase, catalyzing the oxidation of acetosyringon, was also reduced by both enzymes. The reduction of phenoxyradicals formed by phenoloxidases (lignin peroxidases, as well as laccases) may be important in preventing repolymerization reactions which we suggest would significantly facilitate lignin degradation.

Carbohydrate Dehydrogenases↗