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1.
Bioremediation of polychlorinated biphenyl-contaminated soil using carvone and surfactant-grown bacteria 总被引:4,自引:0,他引:4
Singer AC Gilbert ES Luepromchai E Crowley DE 《Applied microbiology and biotechnology》2000,54(6):838-843
Partial bioremediation of polychlorinated biphenyl (PCB)-contaminated soil was achieved by repeated applications of PCB-degrading
bacteria and a surfactant applied 34 times over an 18-week period. Two bacterial species, Arthrobacter sp. strain B1B and Ralstonia eutrophus H850, were induced for PCB degradation by carvone and salicylic acid, respectively, and were complementary for the removal
of different PCB congeners. A variety of application strategies was examined utilizing a surfactant, sorbitan trioleate, which
served both as a carbon substrate for the inoculum and as a detergent for the mobilization of PCBs. In soil containing 100 μg
Aroclor 1242 g−1 soil, bioaugmentation resulted in 55–59% PCB removal after 34 applications. However, most PCB removal occurred within the
first 9 weeks. In contrast, repeated addition of surfactant and carvone to non-inoculated soil resulted in 30–36% PCB removal
by the indigenous soil bacteria. The results suggest that bioaugmentation with surfactant-grown, carvone-induced, PCB-degrading
bacteria may provide an effective treatment for partial decontamination of PCB-contaminated soils.
Received: 9 March 2000 / Received revision: 27 June 2000 / Accepted: 16 July 2000 相似文献
2.
E. Kostyál M. Borsányi L. Rigottier-Gois M. S. Salkinoja-Salonen 《Applied microbiology and biotechnology》1998,50(5):612-622
The dechlorinating and genotoxicity-removing activities of nitrifying fluidized-bed reactor biomass towards chlorinated organic
compounds in water were shown at level below 1 ppm. The removal rates of adsorbable organic halogens were 200 μg Cl (g VS
day)−1 for chlorinated humic ground water and 50 μyg Cl (g VS day)−1 for chlorinated lake water when studied in batch mode. In a sequenced batch mode the removal rates μg Cl (g VS day)−1] were 2000 from chlorohumus, 1400–1800 from chlorophenols in chlorinated ground water, and 430–720 from chlorohumus in chlorinated
lake water. Genotoxicity was removed to a large extent (60%–80%) from the chlorinated waters upon incubation with nitrifying
reactor biomass. 2,6-Di-, 2,4,6-tri and 2,3,4,6-tetrachlorophenols competed with chlorinated water organohalogens for dechlorination.
The dechlorination of chlorophenols and chlorohumus required no ammonia and was not prevented by inhibitors of ammonia oxidation,
nitrapyrin, parathion, sodium diethyldithiocarbamate, or allylthiourea. Electron microscopical inspection of the biomass showed
the dominance of clusters of bacteria resembling known nitrifying species, Nitrosomonas, Nitrobacter, and Nitrosospira. This was supported by polymerase chain reaction amplification of the biomass DNA with four different primers, revealing
the presence of 16S rDNA sequences assignable to the same species. The most intensive band obtained with the Nitroso4E primer
was shown to be closely related to Nitrosomonas europaea by restriction analysis.
Received: 27 March 1998 / Received revision: 30 July 1998 / Accepted: 31 July 1998 相似文献
3.
The thermotolerant fungus, Aspergillus niger NCIM 563, was used for production of extracellular phytase on agricultural residues: wheat bran, mustard cake, cowpea meal,
groundnut cake, coconut cake, cotton cake and black bean flour in solid state fermentation (SSF). Maximum enzyme activity
(108 U g−1 dry mouldy bran, DMB) was obtained with cowpea meal. During the fermentation phytic acid was hydrolysed completely with a
corresponding increase in biomass and phytase activity within 7 days. Phosphate in the form of KH2PO4 (10 mg per 100 g of agriculture residue) increased phytase activity. Among various surfactants added to SSF, Trition X-100
(0.5%) exhibited a 30% increase in phytase activity. The optimum pH and temperature of the crude enzyme were 5.0 and 50°C
respectively. Phytase activity (86%) was retained in buffer of pH 3.5 for 24 h. The enzyme retained 75% of its activity on
incubation at 55°C for 1 h. In the presence of 1 mM K+ and Zn2+, 95% and 55% of the activity were retained. Scanning electron microscopy showed a high density growth of fungal mycelia on
wheat bran particles during SSF. Journal of Industrial Microbiology & Biotechnology (2000) 24, 237–243.
Received 07 June 1999/ Accepted in revised form 18 December 1999 相似文献
4.
Production of ligninolytic enzymes and synthetic lignin mineralization by the bird's nest fungus Cyathus stercoreus 总被引:3,自引:0,他引:3
Production of ligninolytic enzymes and degradation of 14C-ring labeled synthetic lignin by the white-rot fungus Cyathus stercoreus ATCC 36910 were determined under a variety of conditions. The highest mineralization rate for 14C dehydrogenative polymerizates (DHP; 38% 14CO2 after 30 days) occurred with 1 mM ammonium tartrate as nitrogen source and 1% glucose as additional carbon source, but levels
of extracellular laccase and manganese peroxidase (MnP) were low. In contrast, 10 mM ammonium tartrate with 1% glucose gave
low mineralization rates (10% 14CO2 after 30 days) but higher levels of laccase and manganese peroxidase. Lignin peroxidase was not produced by C. stercoreus under any of the studied conditions. Mn(II) at 11 ppm gave a higher rate of 14C DHP mineralization than 0.3 or 40 ppm, but the highest manganese peroxidase level was obtained with Mn(II) at 40 ppm. Cultivation
in aerated static flasks gave rise to higher levels of both laccase and manganese peroxidase compared to the levels in shake
cultures. 3,4-Dimethoxycinnamic acid at 500 μM concentration was the most effective inducer of laccase of those tested. The
purified laccase was a monomeric glycoprotein having an apparent molecular mass of 70 kDa, as determined by calibrated gel
filtration chromatography. The pH optimum and isoelectric point of the purified laccase were 4.8 and 3.5, respectively. The
N-terminal amino acid sequence of C. stercoreus laccase showed close homology to the N-terminal sequences determined from other basidiomycete laccases. Information on C. stercoreus, whose habitat and physiological requirements for lignin degradation differ from many other white-rot fungi, expands the
possibilities for industrial application of biological systems for lignin degradation and removal in biopulping and biobleaching
processes.
Received: 29 January 1999 / Received revision: 5 July 1999 / Accepted: 9 July 1999 相似文献
5.
Trametes versicolor was shown to produce extracellular laccase during surface cultivation on glucose, wheat straw and beech wood. Growth on both
wheat straw and beech wood led to an increase as high as 3.5-fold in extracellular laccase activity, in comparison with growth
on glucose. The corresponding yields in fungal biomass reached only about 20% of the value obtained on glucose. Manganese
peroxidase activity␣appeared during growth on wheat straw and beech wood. Mycelia grown on glucose, wheat straw and beech
wood also showed intracellular laccase activities, monitored with 2,6-dimethoxyphenol, 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulphonic
acid), 4-hydroxy-3,5-dimethoxybenzaldehyde azine (syringaldazine) and 3,4-dihydroxyphenylalanine (l-DOPA). Assaying intracellular laccase with 2,6-dimethoxyphenol, syringaldazine and l-DOPA showed the maximum oxidation rates to be at pH values different from those producing maximum oxidation rates with extracellular
laccase. In each case most of the total laccase activity was recovered from the culture filtrates. Growth on wheat straw and
beech wood led to increased values for both extra- and intracellular laccase activities, based on fungal dry weight, in comparison
with growth on glucose.
Received: 18 July 1996 / Received revision: 19 November 1996 / Accepted: 23 November 1996 相似文献
6.
The majority of lignin-degrading basidiomycetes are able to depolymerize humic acids. In this presentation the relationship
and possible similarities between enzymes involved in lignin degradation and humic acid depolymerization were examined on
the genetic level. We have cloned fragments of the gene encoding the extracellular ligninolytic enzyme laccase from Clitocybula dusenii, Nematoloma frowardii and a fungal strain designated i63-2, and compared the three sequences with those of several other published laccase genes.
The sequenced fragments displayed a high homology both on the DNA (97%–77%) and amino acid (100%–85%) level. Furthermore,
the expression of this gene in the above-mentioned fungi was demonstrated by a nested polymerase chain reaction with cDNA
as template.
Received: 3 February 1998 / Received revision: 31 August 1998 / Accepted: 3 September 1998 相似文献
7.
Optimization of mycophenolic acid production in solid state fermentation using response surface methodology 总被引:7,自引:0,他引:7
A K Sadhukhan MV Ramana Murthy R Ajaya Kumar E V S Mohan G Vandana C Bhar K Venkateswara Rao 《Journal of industrial microbiology & biotechnology》1999,22(1):33-38
Mycophenolic acid (MPA) can be produced in solid state fermentation. An isolate of Penicillium brevi-compactum ATCC 16024 grown on moist wheat bran produced a titre of 425 mg per kg of wheat bran. Central composite rotatable design
and response surface methodology were employed to derive a statistical model for media optimization towards production of
mycophenolic acid. Five levels with a five factorial design were adopted. The correlation coefficient was 0.82, ensuring a
satisfactory adjustment of the model to the experimental values. This statistical design was very effective in improving the
titre of mycophenolic acid up to 3286 mg per kg of wheat bran.
Received 24 July 1998/ Accepted in revised form 4 December 1998 相似文献
8.
R. Céspedes A. Maturana U. Bumann M. Bronfman B. González 《Applied microbiology and biotechnology》1996,46(5-6):631-637
The removal of chlorophenolic compounds from kraft mill effluents bleached with chlorine (cBKME) or chlorine plus hemicellulases
(bBKME) was studied in reactors of aerobic treatment lagoons. In these laboratory models, a stable microbial population removed
biochemical oxygen demand at similar rates of the mill lagoon. Complete removal of nine chlorophenols and chloroguaiacols
during microbial treatment of these effluents was detected by gas chromatography. Abiotic removal was only observed with 2,4-dichlorophenol
and 2,4,5-trichlorophenol. There were no significant differences in degradative ability between microorganisms acclimated
to grow in reactors fed with cBKME or bBKME. The latter had a lower content of adsorbable organic halogen and chlorophenols
than cBKME. Microorganisms acclimated to cBKME or bBKME were only able to grow on phenol or guaiacol as sole carbon source.
However, these microorganisms removed (0.1–0.5 mM) 4-chlorophenol, 2,4-dichlorophenol and 2,4-dichlorophenoxyacetate with
BKME as primary carbon source. Under these conditions, 2,4,6- and 2,4,5-trichlorophenol, 4,5-dichloroguaiacol, 4,5,6-trichloroguaiacol
and tetrachloroguaiacol were not removed. These results suggest that the microbial removal of bleaching chlorophenols and
chloroguaiacols during aerobic treatment, probably takes place only because of their very low concentration (1–200 ppb) in
BKME.
Received: 12 February 1996 / Received revision: 10 June 1996 / Accepted: 22 June 1996 相似文献
9.
Continuous vapor-phase trichloroethylene biofiltration using hydrocarbon-enriched compost as filtration matrix 总被引:3,自引:0,他引:3
Two sources of finished compost material were examined for the capacity to support trichloroethylene(TCE)-degrading microbial
populations in a gas-phase bioreactor. Gaseous hydrocarbon was passed through the bioreactor to stimulate cometabolic oxidation
of TCE. Significant differences in TCE removal efficiencies were observed between the two compost types, and between hydrocarbon-stimulated
and non-stimulated compost. At an average column retention time of 5.6 min, deciduous leaf debris compost removed more than
95% of a 5–50 ppm (by vol.) TCE gas stream, whereas less than 15% removal was observed under similar conditions with a woodchip
and bark compost. Trichloroethylene removal efficiency varied with the hydrocarbon-stimulation regime employed, although propane
and methane stimulated TCE degradation equally well. Amendment of compost with granular activated carbon substantially increased
biological TCE removal. Differences in TCE removal efficiencies observed between the two compost types and between hydrocarbon-stimulated
and non-stimulated composts were investigated in terms of changes in the overall heterotrophic microbial populations by using
community-level physiological profile analysis.
Received: 14 April 1997 / Received revision: 21 July 1997 / Accepted: 25 August 1997 相似文献
10.
Sathish T Lakshmi GS Rao ChS Brahmaiah P Prakasham RS 《Letters in applied microbiology》2008,47(4):256-262
Aim: Investigation of mixture‐design impact on glutaminase production by isolated Bacillus sp. Methods and Results: An augmented simplex centroid design was used to optimize a three (wheat bran, Bengal gram husk and palm seed fibre) component mixture for glutaminase production. Selected substrate materials showed impact on glutaminase production values at individual level by Bengal gram husk [2789 U gds?1 (gram dry substrate] and in two‐level combination with wheat bran and Bengal gram husk (maximum of 3300 U gds?1). Conclusion: Bengal gram husk is the most suitable substrate medium for glutaminase production by Bacillus sp. Maximum glutaminase production is achieved using solid‐substrate mixture at two‐level combinations in the ratio of 66 : 34 for Bengal gram husk and wheat bran, respectively. Significance and Impact of the Study: The present study has significance in large‐scale production of glutaminase at commercial level with the use of multi‐substrate rather than single‐substrate/support material. 相似文献
11.
BTEX catabolism interactions in a toluene-acclimatized biofilter 总被引:1,自引:0,他引:1
BTEX substrate interactions for a toluene-acclimatized biofilter consortium were investigated. Benzene, ethylbenzene, o-xylene, m-xylene and p-xylene removal efficiencies were determined at a loading rate of 18.07 g m−3 h−1 and retention times of 0.5–3.0 min. This was also repeated for toluene in a 1:1 (m/m) ratio mixture (toluene: benzene, ethylbenzene,
or xylene ) with each of the other compounds individually to obtain a final total loading of 18.07 g m−3 h−1. The results obtained were modelled using Michaelis–Menten kinetics and an explicit finite difference scheme to generate
v
max and K
m parameters. The v
max/K
m ratio (a measure of the catalytic efficiency, or biodegradation capacity, of the reactor) was used to quantify substrate
interactions occurring within the biofilter reactor without the need for free-cell suspended and monoculture experimentation.
Toluene was found to enhance the catalytic efficiency of the reactor for p-xylene, while catabolism of all the other compounds was inhibited competitively by the presence of toluene. The toluene-acclimatized
biofilter was also able to degrade all of the other BTEX compounds, even in the absence of toluene. The catalytic efficiency
of the reactor for compounds other than toluene was in the order: ethylbenzene>benzene>o-xylene>m-xylene>p-xylene. The catalytic efficiency for toluene was reduced by the presence of all other tested BTEX compounds, with the greatest
inhibitory effect being caused by the presence of benzene, while o-xylene and p-xylene caused the least inhibitory effect. This work illustrated that substrate interactions can be determined directly from
biofilter reactor results without the need for free-cell and monoculture experimentation.
Received: 13 April 2000 / Received revision: 20 July 2000 / Accepted: 27 July 2000 相似文献
12.
Laccase, purified from Coriolus versicolor, removed pentachlorophenol (PCP) from solution at pH 5, depending on initial PCP concentration and amount of laccase. With
100 units of laccase, 100% of 25 μg ml−1 PCP and 60% of 200 μg ml−1 PCP were removed respectively over 72 h. No free chloride was released in the reaction. In reaction with 100 μg PCP, products
were primarily polymers (about 80,000 MW) with only 2–3 pg of o- and p-chloranils formed. Polymers were stable to acid hydrolysis and no release of PCP, or other low-molecular-weight products,
was detected over several weeks. Laccase has a potential use in the biotreatment of aqueous effluents containing PCP, with
polymerised products being removed from solution due to their high molecular weight.
Received: 7 June 1999 / Received revision: 18 August 1999 / Accepted: 2 September 1999 相似文献
13.
Purification and properties of a novel raw starch degrading cyclomaltodextrin glucanotransferase from Bacillus firmus 总被引:3,自引:0,他引:3
B. N. Gawande A. Goel A. Y. Patkar S. N. Nene 《Applied microbiology and biotechnology》1999,51(4):504-509
A novel raw starch degrading cyclomaltodextrin glucanotransferase (CGTase; E.C. 2.4.1.19), produced by Bacillus firmus, was purified to homogeneity by ultrafiltration, affinity and gel filtration chromatography. The molecular weight of the
pure protein was estimated to be 78 000 and 82 000 Da, by SDS-PAGE and gel filtration, respectively. The pure enzyme had a
pH optimum in the range 5.5–8.5. It was stable over the pH range 7–11 at 10 °C, and at pH 7.0 at 60 °C. The optimum temperature
for enzyme activity was 65 °C. In the absence of substrate, the enzyme rapidly lost its activity above 30 °C. K
m and k
cat for the pure enzyme were 1.21 mg/ml and 145.17 μM/mg per minute respectively, with soluble starch as the substrate. For cyclodextrin
production, tapioca starch was the best substrate used when gelatinized, while wheat starch was the best substrate used when
raw. This CGTase could degrade raw wheat starch very efficiently; up to 50% conversion to cyclodextrins was obtained from
150 g/l starch without using any additives. The enzyme produced α-, β- and γ-cyclodextrins in the ratio of 0.2:9.2:0.6 and
0.2:8.6:1.2 from gelatinized tapioca starch and raw wheat starch with 150 g/l concentration respectively, after 18 h incubation.
Received: 25 September 1998 / Received revision: 15 December 1998 / Accepted: 21 December 1998 相似文献
14.
Removal of phenols from mixtures by co-immobilized laccase/tyrosinase and Polyclar adsorption 总被引:3,自引:0,他引:3
A Krastanov 《Journal of industrial microbiology & biotechnology》2000,24(6):383-388
An enzymatic method for removal of phenols from their mixtures was investigated. Phenols in an aqueous solution were removed
after a two-step treatment with co-immobilized laccase and tyrosinase and Polyclar (polyvinylpolypyrrolidone). A laccase from
Pyricularia oryzae and mushroom tyrosinase were co-immobilized on Mikroperl in a fixed-bed tubular bioreactor by a rapid and simple method.
The support immobilized 95% of the total laccase units and 35% of the total tyrosinase units. Different mixtures of phenols
were passed through the column with co-immobilized laccase and tyrosinase. This method removed 42–90% of different phenolic
substances by a single passage through the bioreactor. The second step employed Polyclar for additional removal of phenolic
substances from mixtures. The degree of removal depends on the nature of the phenols. Complete removal was achieved for a-naphthol,
2,4-dichlorophenol, 4-methoxyphenol, b-naphthol, 4-chloro-3-methylphenol and catehin. The operational stability of the immobilized
system was 10–90 h depending on the substrate. The biocatalyst was capable of continuous transformation of different phenols
in mixtures. Journal of Industrial Microbiology & Biotechnology (2000) 24, 383–388.
Received 12 August 1999/ Accepted in revised form 18 February 2000 相似文献
15.
López-Contreras AM Claassen PA Mooibroek H De Vos WM 《Applied microbiology and biotechnology》2000,54(2):162-167
Domestic organic waste (DOW) collected in The Netherlands was analysed and used as substrate for acetone, butanol and ethanol
(ABE) production. Two different samples of DOW, referred to as fresh DOW and dried DOW, were treated by extrusion in order
to expand the polymer fibres present and to obtain a homogeneous mixture. The extruded material was analysed with respect
to solvent and hot water extractives, uronic acids, lignin, sugars and ash. The total sugar content in the polymeric fractions
of the materials varied from 27.7% to 39.3% (w/w), in which glucose represented the 18.4 and 25.1% of the materials, for fresh
and dried DOW, respectively. The extruded fresh DOW was used as substrate for the ABE fermentation by the solventogenic strain
Clostridium acetobutylicum ATCC 824. This strain was grown on a suspension of 10% (w/v) DOW in demineralised water without further nutrient supplement.
This strain produced 4 g ABE/100 g extruded DOW. When C. acetobutylicum ATCC 824 was grown on a suspension of 10% (w/v) DOW hydrolysed by a combination of commercial cellulases and β-glucosidases,
the yield of solvents increased to 7.5 g ABE/100 g extruded DOW. The utilisation of sugar polymers in both hydrolysed and
non-hydrolysed DOW was determined, showing that only a small proportion of the polymers had been consumed by the bacteria.
These results indicate that growth and ABE production on DOW is mainly supported by soluble saccharides in the medium.
Received: 5 November 1999 / Received revision: 21 February 2000 / Accepted: 25 February 2000 相似文献
16.
Callus was induced from the epicotyl of S. aculeatissimum, and the relation between culture conditions and the production of steroidal saponins in the callus was studied. The results
indicated that the callus produced the steroidal saponins aculeatiside A and B. The highest production of steroidal saponins
occurred at the middle of the log phase. Optimal conditions for the production of steroidal saponins were culturing on MS
basal medium supplemented with the combination of 0.05 ppm or 0.1 ppm NAA and 10 ppm BA, and fructose as a carbon source,
in the dark at 25 °C. Under these optimal conditions, the callus produced 0.8% (per dry weight) steroidal saponins, or 0.32%
aculeatiside A and 0.48% aculeatiside B.
Received: 24 December 1999 / Revision received: 21 February 2000 / Accepted: 16 May 2000 相似文献
17.
Two wheat (Triticum aestivum L.) cultivars, one aluminium tolerant (Atlas 66) and one sensitive (Scout 66), were grown in a continuous-flow culture system
(≤pH 5.0) containing aluminium (0–100 μM) and silicon (0–2000 μM) in factorial combination. Treatment with silicon resulted
in a highly significant amelioration of aluminium toxicity as assessed by root growth in both cultivars. Amelioration was
influenced by wheat cultivar and silicon concentration, as 2000 μM silicon significantly ameliorated the toxic effects of
100 μM aluminium in Atlas 66, and only 5 μM silicon alleviated the effect of 1.5 μM aluminium on Scout 66. Nutrient medium
pH was critical, as an amelioration by silicon was apparent only at pH > 4.2 for Atlas 66, and at pH > 4.6 for Scout 66. Silicon
neither reduced levels of toxic aluminium species in the growth solutions, nor the amount of aluminium taken up by roots.
In experiments to assess exudation of malate by Atlas 66 roots treated with 100 μM aluminium, the presence of 2000 μM silicon
(pH 4.6) was found to have a negligible effect on exudation. In contrast, citrate, a known aluminium chelator, reduced aluminium-induced
exudation of malate at 5–40 μM and completely inhibited it at 100 μM citrate. The results indicate that silicon does not reduce
aluminium phytotoxicity as a result of aluminium/silicon interactions in the external media, and that the mechanism of amelioration
has an in planta component.
Received: 22 April 1997 / Accepted: 16 August 1997 相似文献
18.
Effect of flow rate on heavy metal accumulation by rotating biological contactor (RBC) biofilms 总被引:1,自引:0,他引:1
Immobilized biofilms are effective in heavy metal removal. The current studies investigated the use of rotating biological
contactor (RBC) biofilms in treatment of a wastewater containing cadmium, copper and zinc, each at a concentration of 100 mg
L−1. In particular, the influence of hydraulic retention time (HRT) on metal accumulation was studied. Longer HRTs (>12 h) were
associated with greater metal removal than short HRTs, particularly with regard to cadmium and zinc. The system was also shown
to operate successfully over an extended period of time, at an HRT of 24 h, with removal efficiencies of approximately 34%,
85% and 57% for Cd2+, Cu2+ and Zn2+ respectively after 5–8 weeks contact. Journal of Industrial Microbiology & Biotechnology (2000) 24, 244–250.
Received 28 July 1999/ Accepted in revised form 21 December 1999 相似文献
19.
Bacillus subtilis CBTK 106, isolated from banana wastes, produced high titres of α-amylase when banana fruit stalk was used as substrate in
a solid-state fermentation system. The effects of initial moisture content, particle size, cooking time and temperature, pH,
incubation temperature, additional nutrients, inoculum size and incubation period on the production of α-amylase were characterised.
A maximum yield of 5 345 000 U mg-1 min-1 was recorded when pretreated banana fruit stalk (autoclaved at 121 °C for 60 min) was used as substrate with 70% initial
moisture content, 400 μm particle size, an initial pH of 7.0, a temperature of 35 °C, and additional nutrients (ammonium sulphate/sodium
nitrate at 1.0%, beef extract/peptone at 0.5%, glucose/sucrose/starch/maltose at 0.1% and potassium chloride/sodium chloride
at 1.0%) in the medium, with an inoculum-to-substrate ratio of 10% (v/w) for 24 h. The enzyme yield was 2.65-fold higher with
banana fruit stalk medium compared to wheat bran.
Received: 18 April 1995/Received last revison: 6 May 1996/Accepted: 9 May 1996 相似文献
20.
Kumarasamy Murugesan In-Hee Yang Young-Mo Kim Jong-Rok Jeon Yoon-Seok Chang 《Applied microbiology and biotechnology》2009,82(2):341-350
In this study, we investigated the efficacy of phenolic extract of wheat bran and lignin-related phenolic compounds as natural
redox mediators on laccase-mediated transformation of malachite green (MG) using purified laccase from the white-rot fungus
Ganoderma lucidum. G. lucidum laccase was able to decolorize 40.7% MG dye (at 25 mg l−1) after 24 h of incubation. Whereas, the addition of phenolic extract of wheat bran enhanced the decolorization significantly
(p < 0.001) by two- to threefold than that of purified laccase alone. Among various natural phenolic compounds, acetovanillone,
p-coumaric acid, ferulic acid, syringaldehyde, and vanillin were the most efficient mediators, as effective as the synthetic
mediator 1-hydroxybenzotriazole. Characterization of MG transformation products by HPLC, UV–Vis, and liquid chromatography-mass
spectrometry-electrospray ionization analysis revealed that N-demethylation was the key mechanism of decolorization of MG by laccase. Growth inhibition test based on mycelial growth inhibition
of white rot fungus Phanerochaete chrysosporium revealed that treatment with laccase plus natural mediators effectively reduced the growth inhibitory levels of MG than that
of untreated one. Among all the tested compounds, syringaldehyde showed the highest enhanced decolorization, as a consequence
reduced growth inhibition was observed in syringaldehyde-treated samples. The results of the present study revealed that the
natural phenolic compounds could alternatively be used as potential redox mediators for effective laccase-mediated decolorization
of MG. 相似文献