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ABSTRACT: BACKGROUND: The utilization of mixed monosaccharides commonly found in the hydrolysates of lignocellulosic biomass was evaluated for power generation in single chamber air cathode mediator-less microbial fuel cells.RESULTS: A similar voltage generation pattern was observed for all the MFCs with different monosaccharide combinations and an external resistance of 1000 Ω. However, the different monosaccharide utilization rates ranging from 212 mg L−1 h−1 to 389 mg L−1 h−1 indicate the presence of preferential utilization of different monosaccharides. Three volatile fatty acids (VFAs), including acetic, propionic and butyric acids were detected as the main intermediates, which were generated mainly through a fermentation process.CONCLUSION: VFAs produced from initial monosaccharides contributed to a significant portion of the total electricity generated, and the fermentation process outcompeted the electricity generation process when a mixed bacterial culture was used. Copyright © 2011 Society of Chemical Industry
Journal of Chemical Technology & Biotechnology 01/2011; 86(4):570 - 574. · 2.17 Impact Factor
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ABSTRACT: The use of a laccase-mediator system is one of the promising possibilities for an environmentally benign pulp-bleaching process. Thus a better understanding of the mechanism for the oxidation of lignin by a laccasemediator system would facilitate the commercialization of such a system for pulp bleaching. By using 1-hydroxybenzotriazole (1-HBT) as a mediator, it was found to be partly regenerated during the oxidation of a lignin dimer, 1-(3, 4-dimethoxyphenyl)-2-(2-methoxyphenoxy)propan-1, 3-diol (I). A free radical of 1-HBT, generated by laccase, was probably responsible for the oxidation of I. The free radical of 1-HBT was, however, transformed to benzotriazole, which could not mediate the oxidation of I. The hypothesis that 1-HBT acted as an activator or a co-substrate for laccase was not confirmed. Active oxygen species such as hydroxyl free radical (HO•) and superoxide (O2•-) were also found not to be involved in the oxidation of I.
Biotechnology and Applied Biochemistry 12/2010; 27(3):239 - 243. · 1.53 Impact Factor
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ABSTRACT: Abstract Nanocrystalline cellulose (NCC) was prepared by sulfuric acid hydrolysis of microcrystalline cellulose. A differential centrifugation technique was studied to obtain NCC whiskers with a narrow size distribution. It was shown that the volume of NCC in different fractions had an inverse relationship with relative centrifugal force (RCF). The length of NCC whiskers was also fractionized by differential RCF. The aspect ratio of NCC in different fractions had a relatively narrow range. This technique provides an easy way of producing NCC whiskers with a narrow size distribution.
Cellulose. 01/2009; 16(3):455-465.
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ABSTRACT: Microcrystalline cellulose (MCC) was investigated to partially replace silica in rubber composites. The partial replacement of silica with MCC significantly reduced the energy required for dispersion of fillers in rubber matrix and lowered the internal temperature during the compounding. Moreover, the partial replacement of silica with MCC reduced Mooney viscosity, apparent shear stress, and apparent shear viscosity of the rubber composites, which facilitated the manufacturing process of the rubber composites. The replacement of up to 18% silica with MCC did not negatively affect the mechanical properties of the unaged and aged rubber composites. The partial replacement of silica with MCC also improved the heat resistance, did not significantly change the tanδ of rubber composites containing up to 11.8% of MCC at low temperature and decreased the tanδ of all rubber composites at high temperature. However, addition of MCC slightly decreased tear strength and hot tear strength of the rubber composites.
Composites Part A-applied Science and Manufacturing - COMPOS PART A-APPL SCI MANUF. 01/2009; 40(10):1597-1605.
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ABSTRACT: Six polyalcohols derived from lignocellulosic carbohydrates were investigated as carbon sources for electricity generation in single-chamber mediator-less microbial fuel cells (MFCs) for the first time. Electricity was directly generated from all polyalcohols tested, including pentitols (xylitol, arabitol, and ribitol) and hexitols (galactitol, mannitol, and sorbitol). Bacterial cultures initially enriched using acetate could be adapted to these substrates with varied adaptation times. The resultant maximum power density ranged from 1490+/-160 mW/m(2) to 2650+/-10 mW/m(2) at current densities between 0.58 mA/cm(2) and 0.78 mA/cm(2). Galactitol generated the highest maximum power density, while mannitol resulted in the lowest one. The estimated maximum voltage output at an external resistance of 120 Omega ranged between 0.24 V and 0.34 V with half saturation kinetic constants varied from 298 mg/L to 753 mg/L. The removal of chemical oxygen demand (COD) was above 91% for all polyalcohols except sorbitol (71%). Denaturing gradient gel electrophoresis (DGGE) of PCR-amplified 16S rRNA gene segments of the anode biofilms showed the influence of substrates (polyalcohols) on the anode microbial populations.
Biosensors & bioelectronics 08/2008; 24(4):855-60. · 5.43 Impact Factor
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ABSTRACT: Journal of Power Sources j o u r n a l h o m e p a g e : w w w . e l s e v i e r . c o m / l o c a t e / j p o w s o u r a b s t r a c t Lignocellulosic biomass is an attractive fuel source for MFCs due to its renewable nature and ready avail-ability. Furan derivatives and phenolic compounds could be potentially formed during the pre-treatment process of lignocellulosic biomass. In this study, voltage generation from these compounds and the effects of these compounds on voltage generation from glucose in air-cathode microbial fuel cells (MFCs) were examined. Except for 5-hydroxymethyl furfural (5-HMF), all the other compounds tested were unable to be utilized directly for electricity production in MFCs in the absence of other electron donors. One furan derivate, 5-HMF and two phenolic compounds, trans-cinnamic acid and 3,5-dimethoxy-4-hydroxy-cinnamic acid did not affect electricity generation from glucose at a concentration up to 10 mM. Four phenolic compounds, including syringaldeyhde, vanillin, trans-4-hydroxy-3-methoxy, and 4-hydroxy cin-namic acids inhibited electricity generation at concentrations above 5 mM. Other compounds, including 2-furaldehyde, benzyl alcohol and acetophenone, inhibited the electricity generation even at concentra-tions less than 0.2 mM. This study suggests that effective electricity generation from the hydrolysates of lignocellulosic biomass in MFCs may require the employment of the hydrolysis methods with low furan derivatives and phenolic compounds production, or the removal of some strong inhibitors prior to the MFC operation, or the improvement of bacterial tolerance against these compounds through the enrichment of new bacterial cultures or genetic modification of the bacterial strains.
Journal of Power Sources 01/2008; 180:162-166. · 4.95 Impact Factor
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Macromolecular Rapid Communications 03/2005; 26(7):529 - 532. · 4.60 Impact Factor
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Macromolecular Rapid Communications 10/2004; 25(21):1835 - 1838. · 4.60 Impact Factor
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ABSTRACT: This study investigated a new adhesive system, consisting of soy protein isolate (SPI) and Kymene® 557H (simply called Kymene) (a commercial wet-strength agent for paper), that was prepared by mixing SPI and Kymene. Wood
composites bonded with SPI-Kymene adhesive preparations had shear strengths comparable to or higher than those bonded with
commercial phenol formaldehyde resins. Wood composites bonded with the new adhesive system had high water resistance and retained
relatively high strength even after they had undergone a boiling-water test. The new adhesive system is formaldehyde-free,
easy to use, and environmentally friendly. Kymene was proposed to serve as a curing agent in SPI-Kymene adhesives.
Journal of Oil & Fat Industries 04/2004; 81(5):487-491. · 1.77 Impact Factor
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ABSTRACT: The morphology and ligninolytic enzyme production of a recently isolated wood-degrading fungus Trichophyton rubrum LSK-27 was investigated. In submerged cultures, the organism appeared to be an efficient manganese peroxidase (MnP) producer.
When grown in baffled and unbaffled shake flasks with three different working volume/total volume ratios (WV/TV 10, 25 and
50%), the organism displayed notable morphological differences, with variations in pellet shape and size. Cultivation in baffled
flasks with 25% WV/TV resulted in higher MnP and also laccase production as well as an earlier appearance of these enzymes
in culture broth. However, oxygen limitation conditions inhibited MnP and laccase production and resulted in considerable
changes in the morphology of this fungus.
World Journal of Microbiology and Biotechnology 01/2004; 20(4):345-349. · 1.53 Impact Factor
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ABSTRACT: A manganese peroxidase (MnP) from a wood-degrading fungus Trichophyton rubrum LSK-27 was purified to homogeneity by anion-exchange chromatography followed by gel filtration. Molecular mass of the purified enzyme was determined to be about 42 kDa by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS–PAGE). Spectrophotometric analysis of the enzyme revealed one Soret maximum at 407 nm, and two visible peaks at 502 and 644 nm, which are consistent with photometric spectra of other MnPs. Mass spectrometric analysis of the digested protein revealed that it had a very high homology to a unique peroxidase (a hybrid of MnP and lignin peroxidase) from Bjerkandera sp. B33/3. Bjerkandera MnP was able to oxidize veratryl alcohol, whereas T. rubrum LSK-27 MnP could not. T. rubrum LSK-27 MnP had the highest pI of 8.2 among MnPs reported so far. The enzyme was stable at rather high temperatures, and when compared with other MnPs, this MnP was more stable in the presence of high concentrations of H 2 O 2 .
Enzyme and Microbial Technology 01/2004; 35:87-92. · 2.37 Impact Factor
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ABSTRACT: Chitosan-phenolics systems were investigated as wood adhesives. Adhesion between two pieces of wood veneer developed only when all three components-chitosan, a phenolic compound, and laccase-were present. For the adhesive systems containing a phenolic compound with only one phenolic hydroxyl group, adhesive strengths were highly dependent upon the chemical structures of phenolic compounds used in the system and the relative oxidation rates of the phenolic compounds by laccase. The adhesive strengths were also directly related to the viscosity of the adhesive systems. However, for the adhesive systems containing a phenolic compound with two or three phenolic hydroxyl groups adjacent to each other, no correlations among adhesive strengths, relative oxidation rates of the phenolic compounds by laccase, and viscosities were observed. The adhesion mechanisms of these chitosan-phenolics systems were proposed to be similar to those of mussel adhesive proteins.
Journal of Biotechnology 05/2003; 102(2):199-207. · 3.05 Impact Factor
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ABSTRACT: In order to enhance the bleaching effect of manganese peroxidase (MnP), unsaturated fatty acids, thiol-containing compounds and various other organic compounds were applied in pulp bleaching experiments with MnP. Thiol-containing compounds did not improve the pulp bleaching effect by MnP. Some unsaturated fatty acids, linoleic acid and linolenic acid provided a better pulp bleaching effect than Tween 80. The correlation between the number of C=C bonds in a fatty acid and its pulp bleaching effect was also investigated. The MnP pulp bleaching capability was shown to depend on the carboxylic acid used. A combination of Tween 80 and a carboxylic acid resulted in higher pulp brightness than that obtained with Tween 80 alone. A laccase mediator, 3-hydroxy-1,2,3-benzotriazin-4(3H)-one, could also enhance the MnP pulp bleaching effect.
Bioresource Technology 01/2003; 85(3):249-52. · 4.98 Impact Factor
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ABSTRACT: Mussel protein is a strong and water-resistant adhesive, but is expensive and not readily available. Soy protein is inexpensive, abundant, and annually renewable, but suffers from low adhesive strengths and low water resistance of the bonded products. This study reveals that introducing a key functional group from the marine adhesive protein to soy protein converts the soy protein to a strong and water-resistant wood adhesive.
Macromolecular Rapid Communications 10/2002; 23(13):739 - 742. · 4.60 Impact Factor
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04/2002;
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ABSTRACT: A series of N-hydroxyacetanilide and 1-hydroxybenzotriazole analogues derivatized by various functional substituents were studied with regard to redox potential, oxidation by laccase, oxidative stability, and correlation to the electronic and steric properties of the substituents. It was found that substituents carrying conjugative/π-electron function influenced the redox potential more than substituents carrying inductive/σ-electron function, and that the electron-transfer from an N-hydroxy moiety to laccase was significantly affected by the redox potential. Electron-withdrawing substituents tended to reduce the electron density on the N-hydroxy group, leading to higher redox potential and lower oxidation rate. Bulky substitution or absence of N-phenyl tended to increase the Km of the N-hydroxy group, leading to lower oxidation rate. Oxidized N-hydroxy compounds were stabilized by N-phenyl or N-carbonyl group, but not by N-azo or highly strained structure. Potential implication of these effects on laccase-based, N-hydroxy compound-mediated biocatalysis is discussed.
European Journal of Biochemistry. 12/2001; 268(15):4169 - 4176.
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ABSTRACT: 1-Hydroxybenzotriazole, violuric acid, and N-hydroxyacetanilide are three N-OH compounds capable of mediating a range of laccase-catalyzed biotransformations, such as paper pulp delignification and degradation of polycyclic hydrocarbons. The mechanism of their enzymatic oxidation was studied with seven fungal laccases. The oxidation had a bell-shaped pH-activity profile with an optimal pH ranging from 4 to 7. The oxidation rate was found to be dependent on the redox potential difference between the N-OH substrate and laccase. A laccase with a higher redox potential or an N-OH compound with a lower redox potential tended to have a higher oxidation rate. Similar to the enzymatic oxidation of phenols, phenoxazines, phenothiazines, and other redox-active compounds, an “outer-sphere” type of single-electron transfer from the substrate to laccase and proton release are speculated to be involved in the rate-limiting step for N-OH oxidation.
Applied and Environmental Microbiology 06/2000; · 3.83 Impact Factor
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ABSTRACT: Although bleaching of kraft pulps with MnP or xylanase have been studied extensively, their synergistic effects have yet to be demonstrated. We report here for the first time that a combination of MnP and xylanase has pulp bleaching effects far superior to those of the individual enzymes used sequentially. Bleaching of hardwood kraft pulp with MnP and xylanase for 24 hours followed by a single alkaline/hydrogen peroxide treatment increased pulp brightness from 35.3 to 78.1% (ISO) and decreased the kappa number from 13.7 to 4.3. We demonstrated that this bleaching effect was a synergistic action between the enzymes rather than an addition of the brightening abilities of each individual enzyme. An optimal temperature for the pulp bleaching with MnP and xylanase is 40 o C. The concentration of hydrogen peroxide in the pulp slurry has very important impacts on pulp bleaching effect. A continuous addition of hydrogen peroxide at an appropriate flow rate could enhance the pulp bleaching effect dramatically. Many studies are currently done to increase the efficient utilization of enzymes in pulp delignification and bleaching as the current trend towards chlorine-free bleaching escalates. Among all the wood degrading enzymes the first reported to be useful for pulp bleaching was xylanase (1). A pretreatment of wood pulp with xylanase was found to increase the bleachability of the pulp in subsequent chemical bleaching stages (2). Xylanases were demonstrated to save up to 25% of bleaching chemicals required to reach a desired brightness (3). Although xylanases are currently used in several pulp mills worldwide, their effect on delignification is limited and indirect. Therefore, utilization of ligninolytic enzymes such as manganese peroxidase (MnP) and laccase might be a more efficient way to delignify and bleach pulp. Although both laccase and
Tappi Journal 01/2000; · 0.47 Impact Factor
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ABSTRACT: The white-rot fungus Pycnoporus cinnabarinus produces only one isoform of laccase and traces of a peroxidase which is neither manganese peroxidase (MnP) nor lignin peroxidase (LiP). To test the impact of laccase on pulp bleaching we performed studies with P. cinnabarinus wild type (WT) and its laccase-less mutants on softwood kraft pulp (SWKP) in both static and shake flask cultures. In the static pulp cultures (at 20% pulp consistency in water), after 25 days incubation, P. cinnabarinus wild type increased the pulp brightness from 35 to 59% ISO, and decreased the kappa number from 15 to 5.7. However P. cinnabarinus laccase-less mutants 51 and 85 increased the brightness to only 40.6 and 40.7, and decreased the kappa number to 12 and 13.4, respectively. In the shake flask cultures with pulp suspended in water (at 2% consistency), the wild type increased pulp brightness from 38 to 52.4% ISO, and decreased the kappa number from 12 to 5.9. The laccase-less mutants 51, and 85 increased the brightness only to 43.8 and 40, and decrease the kappa number to 9.2 and 10.6, respectively. These results showed that both in the static and shaking cultures, the laccase-less mutants were very inefficient or unable to bleach pulp which is a clear indication of the importance of laccase for lignin degradation and pulp bleaching by P. cinnabarinus. © 1998 Elsevier Science B.V. All rights reserved.
Journal of biotechnology 01/1998; 66:117-124. · 2.88 Impact Factor
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ABSTRACT: Direct generation of electricity from monosaccharides of lignocellulosic biomass was examined using air cathode microbial fuel cells (MFCs). Electricity was generated from all carbon sources tested, including six hexoses (d-glucose, d-galactose, d(−)-levulose (fructose), l-fucose, l-rhamnose, and d-mannose), three pentoses (d-xylose, d(−)-arabinose, and d(−)-ribose), two uronic acids (d-galacturonic acid and d-glucuronic acid) and one aldonic acid (d-gluconic acid). The mixed bacterial culture, which was enriched using acetate as a carbon source, adapted well to all carbon sources tested, although the adaptation times varied from 1 to 70 h. The maximum power density obtained from these carbon sources ranged from 1240 ± 10 to 2770 ± 30 mW m−2 at current density range of 0.76–1.18 mA cm−2. d-Mannose resulted in the lowest maximum power density, whereas d-glucuronic acid generated the highest one. Coulombic efficiency ranged from 21 to 37%. For all carbon sources tested, the relationship between the maximum voltage output and the substrate concentration appeared to follow saturation kinetics at 120 Ω external resistance. The estimated maximum voltage output ranged between 0.26 and 0.44 V and half-saturation kinetic constants ranged from 111 to 725 mg L−1. Chemical oxygen demand (COD) removal was over 80% for all carbon sources tested. Results from this study indicated that lignocellulosic biomass-derived monosaccharides might be a suitable resource for electricity generation using MFC technology.
Journal of Power Sources.
