Cleavage of humic acids bypenicillium frequentans

Summary Functional group content of undegraded humic acids was compared with that of humic acids which had been partially degraded by a strain ofPenicillium frequentans. It was found that cleavage of humic acids by this organism did not involve reduction of the carboxyl groups. It was suggested that one of the steps involved was hydrolysis of the ether bonds present in humic acids.     

Interference of humic acids and DNA extracted directly from soil in detection and transformation of recombinant DNA from bacteria and a yeast.

A two-step protocol for the extraction and purification of total DNA from soil samples was developed. Crude DNA extracts (100 microliters from 5 g of soil) were contaminated with humic acids at concentrations of 0.7 to 3.3 micrograms/microliters, depending on the type of soil extracted. The coextracted humic acid fraction of a clay silt was similar to a commercially available standard humic acid mixture, as determined by electrophoretic mobility in agarose gels, UV fluorescence, and inhibition assays with DNA-transforming enzymes. Restriction endonucleases were inhibited at humic acid concentrations of 0.5 to 17.2 micrograms/ml for the commercial product and 0.8 to 51.7 micrograms/ml for the coextracted humic acids. DNase I was less susceptible (MIC of standard humic acids, 912 micrograms/ml), and RNase could not be inhibited at all (MIC, > 7.6 mg/ml). High inhibitory susceptibilities for humic acids were observed with Taq polymerase. For three Taq polymerases from different commercial sources, MICs were 0.08 to 0.64 micrograms of the standard humic acids per ml and 0.24 to 0.48 micrograms of the coextracted humic acids per ml. The addition of T4 gene 32 protein increased the MIC for one Taq polymerase to 5.12 micrograms/ml. Humic acids decreased nonradioactive detection in DNA-DNA slot blot hybridizations at amounts of 0.1 micrograms and inhibited transformation of competent Escherichia coli HB101 with a broad-host-range plasmid, pUN1, at concentrations of 100 micrograms/ml. Purification of crude DNA with ion-exchange chromatography resulted in removal of 97% of the initially coextracted humic acids.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effect and potential ecological significance of the interaction of humic acids with two aquatic extracellular proteases

1. The effects of humic acids and fulvic acids on an extracellular serine and metalloprotease purified from a strain of Aeromonas hydrophila isolated from a freshwater wetland were examined. The serine protease was inhibited by humic acids at pH and humic acid concentrations found naturally in the wetland where this strain of A. hydrophila was isolated. The metalloprotease was not inhibited by humic acids at any pH investigated. Fulvic acids had no effect upon either protease. 2. Inhibition of serine protease activity by humic acids was reversed by increasing the pH to 9, as well as increasing the ionic strength by addition of CaCl₂- It was concluded that the interaction between humic acids and the serine protease was primarily ionic. 3. The formation of a humic acid-serine protease complex increased the half-life of enzymatic activity in dilute solutions. Humic acids had no effect on the stability of the metalloprotease. 4. There was no clear effect of humic acids on the growth of A. hydrophila, indicating that either the serine protease is not involved in the rate-limiting step of growth or that sufficient activity exists even when the serine protease is inhibited by humic acids. 5. Increasing the enzymatic lifetime through association with humic acids may be an adaptive mechanism which could result in energy conservation due to a decreased requirement for protein synthesis.     

Fluorescence analysis of photoinduced degradation of ecotoxicants in the presence of humic acids.

The photolysis of humic acids and phenols in water containing humic acids was investigated. Humic acids extracted from peat (Vasuygan Bog, Tomsk Region, Russian Federation) induce the phototransformation of 4-chlorophenol at 365 and 222 nm. Humic acids were characterized by UV-, fluorescence-, IR- and EPR-spectroscopy and laser-induced fluorescence. The influence of humic acids on the phototransformation of phenols in different irradiation conditions was investigated. Comparison of the data on mercury lamp irradiation showed that the most effective phenols degradation was observed under exposure to KrCl* exilamp light (lambda = 222 nm) in the presence of humic acids.     

Effect of<Emphasis Type="Italic">Chalara longipes</Emphasis> on decomposition of humic acids from<Emphasis Type="Italic">Picea abies</Emphasis> needle litter

The effect of the saprotrophic ascomycete Chalara longipes on the decomposition of humic acids was determined in a cultivation experiment. The fungus was incubated in liquid cultures in a full-strength (F system) and an organic nitrogen-free medium (F-N system), both amended with pure humic acids isolated from spruce forest litter. Fungal biomass production was highest in the F system with humic acids and lowest in the F-N system, the effect of organic nitrogen and humic acids being significant (p < 0.05). The presence of organic nitrogen seems to be essential for growth. The fungus utilized humic acids; molar mass distribution in media obtained by gel-permeation chromatography showed decrease in the humic acids fraction. Decolorization of the media reached 75 and 64 % in the F and F-N systems, respectively. The molar mass of humic acids probably also decreased as estimated from the increase in the absorbance A465/A665 (A4/A6) ratio. It is assumed that the utilization of humic acids may be mediated by the production of organic acids (as their components) and production of some oxidative enzymes.     

Effects of humic acids in vitro

Humic acids are known for their overall positive health and productivity effects in animal feeding trials and, controversially, as an aetiological factor of cancer. We tried to assess the in vitro effect of humic acids from a selected source in Slovakia when used at recommended prophylactic dosage. We investigated antioxidant properties, enzymatic and non-enzymatic antioxidant defence system in liver mitochondria and cultured cancer cell lines in vitro. We observed a significant decrease in superoxide dismutase activity after humic acids treatment irrespective of dissolving in dimethyl sulphoxide or direct addition to mitochondria suspension in a respiration medium. Activities of other antioxidant enzymes measured, such as glutathione peroxidase and glutathione reductase, showed no significant differences from the control as well as the reduced glutathione content. Percentage of inhibition by humic acids of superoxide radical indicated lower efficacy compared with that of hydroxyl radical. Survival of six different cancer cells lines indicated that only the acute T lymphoblastic leukaemia cell line was sensitive to the tested humic acids. Despite relatively low solubility in aqueous solutions, humic acids from the selected source participated in redox regulation. By recapturing the radicals, humic acids reloaded the antioxidant defensive mechanism. Results from in vitro study conducted with humic acids from the natural source showed potential of these substances as promising immunity enhancing agents.     

Energy-driven uptake of humic acids by Aspergillus niger.

The uptake of humic acids by mycelia of Aspergillus niger was demonstrated to be energy-dependent with a sensitivity to sodium azide and to 2,4-dinitrophenol. Greater uptake of humic acids by submerged mycelium occurred at pH 3.0 and at 32 degrees C. The rate of uptake was influenced by the concentration of humic acids with an apparent Km of 0.2 grams/ml and with a Vmax of 0.13 mg humic acids per gram mycelial dry weight.10 min-1. In the absence of added energy source, Vmax of 0.05 mg humic acids per gram mycelial dry wt.10 min-1 was obtained; however, the affinity for humic acids by this uptake system was the same as for the energy-driven process. Apparent binding of humic acids to cell structures was indicated because only 41.8% of the humic acids taken up by the energy-dependent system could be recovered.     

Influence of Naturally Occurring Humic Acids on Biodegradation of Monosubstituted Phenols by Aquatic Bacteria

Samples of the microbial community from Lake Michie, a mesotrophic reservoir in central North Carolina, were adapted to various levels (100 to 1,000 μg/liter) of natural humic acids in chemostats. The humic acids were extracted from water samples from Black Lake, a highly colored lake in the coastal plain of North Carolina. After adaptation, the microbial community was tested for its ability to degrade the monosubstituted phenols m-cresol, m-aminophenol, and p-chlorophenol. Adaptation to increasing levels of humic acids significantly reduced the ability of the microbial communities to degrade all three phenols. The decline in biodegradation was accompanied by a decrease in the number of specific compound degraders in the adapted communities. Short-term exposure of the community to increasing levels of humic acids had no significant effect on the ability of the community to degrade m-cresol. Thus the suppressive effect of humic acids on monosubstituted phenol metabolism was the result of long-term exposure to the humic materials. Increasing the levels of inorganic nutrients fed to the chemostats during the humic acid adaptation had little effect on the suppressive influence of the humic acids, indicating that nutrient limitation was probably not responsible for the metabolic suppression. The results of the study suggest that long-term exposure to humic acids can reduce the ability of microbial communities to respond to monosubstituted phenols.     

Hyphal growth and mycorrhiza formation by the arbuscular mycorrhizal fungus Glomus claroideum BEG 23 is stimulated by humic substances

Effects of humic substances (humic acid or fulvic soil extract) or saprophytic microorganisms (Paecilomyces lilacinus and an unidentified actinomycete) on growth of mycelium and mycorrhiza formation by Glomus claroideum BEG23 were studied in a hydroponic system. Humic substances stimulated root colonization and production of extraradical mycelium by the mycorrhizal fungus. Both humic and fulvic acids tended to decrease populations of culturable bacteria and fungi in the cultivation system, indicating a moderately antibiotic activity. The addition of saprophytic microorganisms able to use humic substances to the cultivation system further stimulated the development of the mycorrhizal fungus. However, stimulation of G. claroideum was also observed when the saprophytic microorganisms were heat-killed, suggesting that their effect was not linked to a specific action on humic substances. The results indicate that humic substances may represent a stimulatory component of the soil environment with respect to arbuscular mycorrhizal fungi.     

Efficacy of artificial humic acid as a selective nutrient in HV agar used for the isolation of soil actinomycetes

The efficacies of various kinds of humic acid, as the source of carbon and nitrogen in HV agar reported in the previous paper, were compared to the selective isolation of soil actinomycetes. The 4 types of natural humic acid, A, B, P and Rp were prepared from different soils, and 3 kinds of artificial humic acid were made from carbohydrates and urea in our laboratory.Among the natural humic acids, type Rp, which has been reported to be associated with an initial state of humification in natural conditions, showed the greatest efficacy.However, one of the artificial humic acids, which was prepared from glucose and urea, was considered to be superior to the Rp natural humic acid: 1) The HV agar containing this artificial humic acid (HV-glucose HA agar) produced the same large number of actinomycete colonies on the plate as that of the HV agar with type Rp soil humic acid (HV-Rp agar). 2) The HV-glucose HA agar restricted the number of bacterial colonies on the plates to one-half of that on HV-Rp agar plates. 3) The quality of natural himic acids varies, whereas artificial ones are more constant and can be made in any laboratory.     

Mass spectrometric techniques for characterisation of platinum–humic substance complexes in soil and street dust samples

Abstract

Increased platinum concentrations have been detected in environmental samples since the introduction of catalytic converters in Europe. It was previously believed that PGE are relatively inert and that the soluble fraction of automobile catalyst emitted PGE is only a few percent. However, new studies suggested that metallic Pt is oxidised in the soil and that the majority of the Pt species could be humic substance complexes.

The aim of the present paper is the characterisation of platinum-humic acid complexes in spiked soil and street dust samples. A number of different soft ionisation mass spectrometric techniques, such as ESI-Q-MS, ESI-ION TRAP-MS and MALDI-TOF-MS have been tested. The ESI mass spectra of the soil humic acids were characterised by high complexity and irreproducibility.

MALDI-TOF-MS was used for humic acid complexes characterisation in positive and negative modes. Positive ionisation was less effective and produced more simple and less informative spectra than negative ionisation. Two different MALDI matrices (CHCA, DHBA) were tested for use with humic substances. DHBA yielded better results, exhibiting superior ionisation efficiency, low spectral background and the matrix peaks were almost completely suppressed causing no interferences with identified analyte peaks. The application of MALDI-TOF-MS shows its suitability for humic substance characterisation. The comparison of the MALDI-spectra of humic acids, extracted from spiked and native soil proved that Pt undergoes transformation in the environment to humic acid complexes.     

Seasonal changes in the concentration and colour of humic substances in some aquatic environments

SUMMARY. 1. Between February and September 1974, concentrations of fulvic and humic acids in waters from a cryoboreal region of the Precambrian Shield in Quebec varied between 0.5–6.1 mg 1⁻¹ and 0.1–6.5 mg 1⁻¹ respectively. Whereas the fulvic acids usually remained relatively constant during this period, humic acids showed appreciable increases.
2. The number and weight average molecular weights of the fulvic acids (∼5000 and ∼22,000 daltons respectively) were lower than those of the humic acids (∼20,000 and ∼75,000 daltons respectively). The average molecular weight of the aquatic humic matter often decreased during late summer and early autumn. During spring floods the molecular weight of fulvic acids increased and that of humic acids declined.
3. Because the aquatic humic acids were more intensely coloured than fulvic acids, they contributed more than 30% of the colour of the water even though they accounted for only 15% of the concentration of humic matter. The colour intensity of both fulvic and humic acids generally appeared to increase during the latter part of the summer, when there was normally a decrease in the value of the colour quotient (E₄/E₆ ratio), indicating the accumulation in the waters of more humified material.     

The inhibition of proteolytic enzyme activity by humic acids]

The inhibitory effect of peat humic acids on the hydrolysis of N-acetyl-L-tyrosine ethyl ester and N-benzoyl-L-leucine methyl ester by alpha-chymotrypsin and subtilism has been studied. Samples of humic acids with M(W) approximately 18,000 have been used in experiments. The results of kinetic studies indicates the mixed type of inhibition of proteinase activity by humic acids. The meanings of inhibition constants under the action of humic acids on alpha-chymotrypsin and subtilism have been calculated.     

加速侵蚀对土壤腐殖酸动态变化的影响

土壤腐殖酸的流失是土壤退化的标志之一。林地被开垦破坏后,土壤腐殖酸的流失程度在坡面上的空间分布与侵蚀方式和侵蚀强度相对应,坡面中部和中下部浅沟沟槽处最为严重,细沟侵蚀区次之,梁峁上部片蚀区相对最弱。侵蚀土壤中的腐殖酸总碳、胡敏酸碳和富啡酸碳含量随开垦年限的增加呈指数减少,其减少程度受侵蚀强度和侵蚀方式的影响。腐殖酸的流失程度与加速侵蚀造成的土壤剖面破坏密切相关。恢复植被可使土壤腐殖酸逐渐增加,土壤肥力得到恢复,土壤退化过程得到逆转。     

Distribution of heavy metals in a sewage oxidation pond and their adsorption in residual solid (sewage sludge ash)

Abstract

Electrometric studies were carried out on the interaction of heavy metal ions such as manganese, chromium, nickel, copper, zinc, cadmium and lead with the extracted organic matter, humic and fulvic acid from the sludge in a sewage oxidation pond. The distribution of heavy metals was between 60 and 97%, which is associated with the solid waste (sludge) of the oxidation pond. The adsorption/removal efficiency of metal ions onto the sludge ash was more than 90% and 97%, respectively, in the pure system. To obtain the ash, the sludge was burnt at 500°C, treated with nitric acid (1+1) to leach out all the metals and then filtered; the residue left on the filter paper was the pure ash. Both this and that coated with organic matter were studied. The adsorption isotherm for metals, humic/fulvic acids and metal-humic/fulvic acid complexes in the metal-free sludge ash and in the organic matter in the pure system were studied using the Freundlich relationship. Good agreement was found suggesting that sediment and humic/fulvic acids have an important role in the mobility, dispersion and sedimentation of metal ions in an aquatic environment. More of these heavy metals are removed in the pure system than in the natural system. This may be due to the lesser availability of humic and fulvic acids in the lagoons during the short detention time of sewage in suspension in the oxidation pond, whereas the sludge which has settled to the bottom of the pond for several years contains rich decomposed organic matter in the form of humic and fulvic acids containing heavy metals. Such pure systems could be useful for the effective removal of heavy metals.     

Humic substances in straw compost with rock phosphate

The production of humic substances and their retention capacities for phosphorus and calcium released during composting of wheat straw with two types of low-grade rock phosphate were examined. Relative quantities of humic acids increased with increase of composting time, while fulvic acids production decreased after 30 days of composting. The addition of both Mussoorie and Hyperphos retarded humic acids production and enhanced fulvic acids production. Molasses incorporation had no effect on humic acids but increased fulvic acids production. The production of humic acids and their retention capacity for P and Ca were greater in the presence of Mussoorie phosphate than in the presence of Hyperphos, but fulvic acids formation was higher with Hyperphos. About 80–85% P and 90–95% Ca retained by the total humic substances were found in the fulvic acids fraction.     

Chemical and structural evolution of humic acids during organic waste composting

The effects of the composting process on the chemical and structural properties of humic acids have been studied in seven different organic waste mixtures from different origin. Only slight changes in elemental composition have been found in the humic acids after the composting process pointing to a more aromatic structure with higher proportions of oxygen and nitrogen. Functional groups were the most sensitive to the changes caused by the composting process showing a marked increase in the total acidity and phenolic, carboxyl and carbonyl groups. Gel permeation chromatography showed a slight increase in the average molecular weight of the humic acids. Infrared spectroscopy did not show important differences in humic acid structure but a clear decrease in the intensity of the bands in the region 3000–2850 cm^-1 corresponding to the aliphatic fractions. As a general result, the composting process yields humic acids in which the elemental and functional composition are closer to that of the more humified soil humic acids.     

Interaction between Diclofenac and Soil Humic Acids

The interaction between the non-steroidal anti-inflammatory drug diclofenac and standard humic acids (HAs) in bulk solution was studied using two complementary analytical methods: UV-Visible spectroscopy and square wave voltammetry. The observed UV-Vis spectra and Ip/V curves suggested that, at our experimental conditions, albeit both substances being negatively charged at pH 6.5, interaction between the pharmaceutical and the soil humic acids may led to the formation of diclofenac-humic acids supramolecules.

Our results could contribute to give information on the behaviour of diclofenac into the soil environment, thus suggesting its migration as HAs-micelles through the coarse soil profile.     

Controlling of Meloidgyne incognita (Tylenchida: Heteroderidae) using nematicides,Linum usitatissimum extract and certain organic acids on four peppers cultivars under greenhouse conditions

Organic acids and plant extracts, which have a nemacidal action and may be used instead of nematicides that pollute the environment, are one way for controlling the pepper root-knot nematode. We provide in this study for a first time a new strategy for management Meloidgyne incognita (Kofoid and White) by using organic acids and plant extract compared to nematicides on four peppers cultivars (Super amarr, Super mard, Super noura and Werta) under greenhouse conditions compared to nematicides. This study aimed to evaluate 0.1% of organic acids (humic and salicylic acid) and 0.1% of Linum usitatissimum extract on plant parameters of pepper varieties (Super amarr, Super mard, Super noura and Werta) and control of M. incognita under greenhouse conditions compared to four nematicides (Oxamyl 24% SL, Fosthiazates 75% EC, Ethoprophos N40% EC and Fenamiphos 40% EC). Our data obtained four nematicides were more effectiveness than other treatments in reduced galls and egg masses of M. incognita. Whilst, humic and salicylic acids have remarkably higher nematicidal activity than L. usitatissimum in all lines of pepper. Therefore, plant extract and organic acids may be used a best alternative of nematicides to control PPNs and caused the longitudinal growth of plant. Also, ultimately reduce environmental risk from nematicide pollution.     

Water repellency of Casuarina windbreaks (Casuarina equisetifolia Forst.) caused by fungi in central Taiwan

The water repellent layer (WRL) in the Casuarina plantation near Taichung Harbor in central Taiwan is mainly due to the development of filamentous fungi. The hyphae of the isolated fungi and the metabolites of the TCHC-5 and TCHC-20 fungi are also significantly hydrophobic. In the soil layers, humic substances decrease the phosphorus fixation and contribute to the formation of WRL. The hydrophobic properties of humic substances are unfavorable for the nutrient cycling in this area. The water contact angles of fulvic acids and humic acids are pH-dependent. Increasing the solution pH value reduces the hydrophobic strength for fulvic acids and/or humic acids. TCHC-15 and TCHC-16 isolated fungi exude strong acidic metabolites (pH 2.7–3.0). This may result in polymerization and/or precipitation of fulvic acids and humic acids and increase the hydrophobic strength of the soil layers. Humic substances with aliphatic chains are the main components that form WRL in soils. Soil pH may be an indicator of the hydrophobic potential for organic matters.