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At least 937 records · Page 52Linked to original sources
PubMed2005

Extracellular enzyme activities of Bjerkandera adusta R59 soil strain, capable of daunomycin and humic acids degradation.

Geotrichum-like strain R59, the anamorphic form of the white-rot fungus, Bjerkandera adusta, was isolated from soil. It was found to completely decolorize and degrade 10% daunomycin post-production effluent during 10 days of incubation at 26 degrees C. Strain R59 produced only low levels of ligninolytic enzymes when grown on wheat straw- or beech sawdust-containing media, but in the presence of humic acids derived from brown coal it synthesized significant amounts of laccase and lipase. This phenomenon was coupled with the fungus entering the idiophase and the appearance of aerial mycelium. B. adusta strain R59 was found to completely decolorize 0.03% humic acids from brown coal and lessive soil and to partially decolorize humic acids isolated from a chernozem during 14 days of growth. This ability of strain R59 could be useful in constructing a new generation of biologically active filters for the purification of humic acids-contaminated drinking waters.

Basidiomycota↗
PubMed2006

Extinction of cells of cyanobacterium Anabaena circinalis in the presence of humic acid under illumination.

Laboratory experiments targeting the effect of humic acid (HA) on the cell lysis of cyanobacterium Anabaena circinalis have been performed. Light irradiation was found to be an important factor for the cell lysis phenomenon, whereas intracellular hydrogen peroxide (H2O2) might be a chemical factor for the process. An exogenous H2O2 concentration of 1.0 mg l(-1) was determined as the threshold for cell survival. Our results indicated that HA or its possible product(s) of photochemical reaction can induce damage to intracellular catalase under artificial illumination, which leads intracellular H2O2 to be accumulated to an abnormally high concentration, eventually resulting in cell death. Moreover, H2O2 released into the culture from dead cells can damage other cells, which in turn brings about the population extinction.

Anabaena↗
PubMed2007

Humic acid effect on pyrene degradation: finding an optimal range for pyrene solubility and mineralization enhancement.

The addition of humic acid (HA) to polycyclic aromatic hydrocarbon (PAH) contaminated systems has been shown to enhance, inhibit, or have no effect on the biodegradation of these PAHs. In this study, the surfactant effects of Elliott soil HA (ESHA) at two pH values were tested. At pH 7.0, ESHA did not behave as a surfactant. At pH 11.8, ESHA acted as a surfactant, as displayed by a decrease in surface tension with increasing concentrations of ESHA. The effect of ESHA on pyrene solubility was tested by adding 0 to 800 microg ESHA/g soil to soil-slurries. Enhancement of pyrene apparent solubility demonstrated a dose- and time-related effect. Broader doses from 0 to 10,080 microg ESHA/g soil and three higher doses from 3,360 to 10,080 microg ESHA/g soil were tested for their effects on pyrene mineralization by indigenous soil microorganisms and a novel PAH-degrading Mycobacterium sp. KMS in soil microcosms, respectively. ESHA amendments between 20 and 200 microg ESHA/g soil were found to consistently increase pyrene mineralization by indigenous microorganisms, while the 10,080 microg ESHA/g soil produced inhibition and all other doses presented no effects. Pyrene degradation by M. KMS was significantly inhibited by the addition of the highest dose of ESHA.

Biodegradation, Environmental↗
PubMed2001

Enhancing pyrene mineralization in contaminated soil by the addition of humic acids or composted contaminated soil.

The addition of composted PAH-contaminated soil to PAH-contaminated soil spiked with 14C-labeled pyrene resulted in rapid mineralization of pyrene (more than 57% after 21 days compared with 3.4% in un-amended soil). The addition of the humic acid fraction of the composted soil also increased the mineralization potential of the soil significantly, but to a lesser extent (37.5% mineralization after 106 days compared with 20.6% in unamended soil). Increasing the humic acid concentration increased mineralization up to a maximum of more than three times the unamended rate, after which the rate of pyrene mineralization decreased, possibly due to inhibitory pH or concentrations of salts. The amendment of PAH-contaminated soil with materials containing humic acids or humic acid extracts is suggested as a method of bioremediation.

Bacteria↗
PubMed1998

Organic halogen removal from chlorinated humic ground water and lake water by nitrifying fluidized-bed biomass characterised by electron microscopy and molecular methods.

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 micrograms Cl (g VS day)-1 for chlorinated humic ground water and 50 micrograms Cl (g VS day)-1 for chlorinated lake water when studied in batch mode. In a sequenced batch mode the removal rates [micrograms 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.

Ammonia↗
PubMed1999

Evidence for and expression of a laccase gene in three basidiomycetes degrading humic acids.

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.

Amino Acid Sequence↗
PubMed2005

Pyrene mineralization capacity increases with compost maturity.

Experiments were conducted to determine the effects of composting or simple addition of compost to the mineralization of n-hexadecane, pyrene and benzo(a)pyrene in soil. Soil (contaminated or clean) was composted with maple leaves and alfalfa. Samples from different composting phases were spiked with radiolabeled and cold n-hexadecane, pyrene or benzo(a)pyrene, placed in aerated microcosms at different temperatures, and monitored for mineralization. It was determined that neither composting nor the addition of compost had any effect on n-alkane or benzo(a)pyrene mineralization. In contrast, the pyrene mineralization rate increased dramatically with the amount of time that soil had been composted. Highest pyrene mineralization rates and extents (more than 60% after 20 days) were obtained when pyrene was in contact with composted soil from the curing stage. Neither thermophiles (55 degrees C) nor fungi were responsible for pyrene mineralization.

Air↗
PubMed2006

Characterization of humic materials extracted from hazelnut husk and hazelnut husk amended soils.

This study was carried out to determine effects of composted hazelnut husk (CHH) on some chemical properties of soil and soil humic acid (HA). Compost application increases organic matter (OM) content of the soil considerably, OM value of 3.18% became 3.89% in 3 years time interval. Before application of compost, the soil pH was found to be 5.37, while after compost application it became 5.61. FTIR characteristics of humic acid/humic acid-like materials extracted from the original hazelnut husk, composted hazelnut husk and composted hazelnut husk amended soil have been investigated. C and O content of humic acid-like/humic acid materials were in the range of 41.4-50.8% and 37.8-50.5%, respectively. The N content of the humic acid/humic acid-like materials are in the expected range for humic materials which is 2-6%. Comparison of FTIR spectra of hazelnut husk and composted hazelnut husk humic acid-like fractions shows that both exhibit similar but not identical series of IR bands indicating the presence of the same functional groups in both samples. The only difference in the spectra seemed to be a decrement in the peak intensities of composted sample compared to uncomposted one. The similar differentiation of the intensities of IR bands of compost applied soil sample has also been observed. The FTIR spectral results show that the characteristics of composted material tend to become similar to that of soil humic acids characteristics in time.

Corylus↗
PubMed2005

Synchronous variation in water chemistry for 80 lakes in southern Sweden.

Variation in water chemistry was studied in 80 lakes in southern Sweden. The lakes had forest dominated catchments. The length of the time series was 14 years. Synchrony was calculated as Pearson's product moment correlation coefficients for all combinations of lakes, i.e. 3160 lake-pairs. The chemical variables studied were non-marine sulphate (SO4*), non-marine calcium (Ca*), absorbance and acid neutralising capacity (ANC). Statistically significant synchrony occurred in 93% of all lake-pairs for SO4*, and between 58 and 67% for absorbance, Ca* and ANC. In 70% of all lake-pairs, the synchrony was >0.71 for SO4*, which means that more than half of the variation in one lake could be explained by the variation in the other lake. For absorbance, Ca* and ANC, about 25% of the lake-pairs had a synchrony >0.71. The relatively high synchrony for SO4* occurred during an overall downward trend in SO4* concentration. The degree of synchrony in our study was at a level comparable to other studies in northern America and England. However, our study included lakes in a much larger area, with distances of up to 500 km between the lakes, while earlier studies were made on small lake districts with lakes located within approximately 50 km. In contrast to these earlier studies, there was no correlation between synchrony and distance, lake characteristics or catchment characteristics. However, when a small subset of 15 lakes in the southeast of Sweden was selected, such relations were found.

Calcium↗
PubMed1984

Electron spin resonance studies of chloroquine-melanin complexes.

Electron spin resonance (ESR) studies of chloroquine complexes with synthetic DOPA-melanin, synthetic catechol-melanin, melanin isolated from bananas and humic acid were performed. Two chloroquine concentrations (5 X 10(-5) M and 1 X 10(-3) M) were used for chloroquine-melanin complex formation. ESR studies showed differences in free radicals concentration depending on melanin origin. It was demonstrated that addition of chloroquine to melanin results in broadening of the melanin ESR signal and is accompanied by changes in the integrated intensity of the analyzed melanin samples.

Catechols↗
PubMed1987

Dicarboxylic acids generated by thermal alteration of kerogen and humic acids.

Significant amounts (up to 2% of organic geopolymers) of low molecular weight (LMW) dicarboxylic acids (C2-C10) have been detected during thermal alteration (270 degrees C, 2 h) of kerogens and humic acids isolated from young or ancient lithified sediments. Their distribution is characterized by predominance of oxalic acid followed by succinic, fumaric and methylsuccinic acids. These acids are probably released by the breakdown of macromolecular structures, which have incorporated biogenic organic compounds, including diacids, during early diagenesis in sediments. Because of their reactivity, LMW diacids may play the following geochemically important roles under natural conditions: (1) the diacids dissolve carbonates and clay minerals to increase porosity and permeability, which enhances migration of oils and gas generated from catagenesis of kerogen dispersed in shale, and (2) the diacids may form organo-metal complexes, which are important for mobilization, transport and accumulation of trace metals in sedimentary basins.

Dicarboxylic Acids↗
PubMed1986

Desmutagenic effect of humic acid.

In the present study, humic acid was not found to be mutagenic and did not inhibit spontaneous mutation. It did, however, inhibit the mutagenicities of benzo[a]pyrene and 3-aminoanthracene (+S9 mix), but not the mutagenicities of 4NQO, AF-2 and MNNG (-S9 mix). 2-Nitrofluorene and 1-nitropyrene do not need S9 mix for activation of their mutagenicities, but an inhibitory effect was observed. Humic acid exerts a desmutagenic effect on mutagens directly before they act on cells. It does not act as an antimutagen which blocks the processes changing normal cells to mutants. The desmutagenic effect was not decreased by heat treatment (120 degrees C, 15 min). Humic acid was fractionated according to molecular weight and the desmutagenic effect increased with an increase in molecular weight. This effect in the fraction with molecular weight exceeding 300 000 was decreased by centrifugation. The desmutagenic ability of humic acid may result from soluble components and adsorption to small particles.

Animals↗
PubMed1989

Humic acids inhibit the formation but not the mutagenicity of N-methyl-N-nitrosourea.

Humic acids in the form of potassium humate (KH), at concentrations exerting a strong inhibitory effect on the formation of N-methyl-N-nitrosourea (MNU) when present during the nitrosation of N-methylurea (MU) at pH 3, did not reduce the mutagenicity of preformed MNU in Tradescantia, clone 4430. The inhibitory effect of 20 mg/ml KH corresponds approximately to that of 3.75 mM (0.66 mg/ml) ascorbic acid towards the formation of MNU from the mixture of 7.5 mM MU + 7.5 mM NaNO2.

Ascorbic Acid↗
PubMed1990

Effects of humic acids, para-aminobenzoic acid and ascorbic acid on the N-nitrosation of the carbamate insecticide propoxur and on the mutagenicity of nitrosopropoxur.

Nitrosation of the carbamate insecticide propoxur at pH 3 and 37 degrees C was determined colorimetrically and found to be time- and sodium nitrite concentration-dependent. Nitrosated propoxur was mutagenic when exposed to the seeds of the higher plant Arabidopsis thaliana but the formation of nitrosopropoxur, the presumed mutagen, was inhibited by humic acids, para-aminobenzoic acid and ascorbic acid. These agents also reduced the mutagenicity of preformed nitrosopropoxur.

4-Aminobenzoic Acid↗