Claudio Cameselle

Study of the degradation of dyes by MnP of Phanerochaete chrysosporium produced in a fixed-bed bioreactor.

The production of ligninolytic enzymes by the fungus Phanerochaete chrysosporium in a fixed-bed tubular bioreactor, filled with cubes of nylon sponge, operating in semi-solid-state conditions, was studied. Maximum individual manganese-dependent peroxidase (MnP) and lignin peroxidase (LiP) activities of 1293 and 225 U/l were detected. The in vitro decolourisation of two structurally different dyes (Poly R-478, crystal violet) by the extracellular liquid obtained in the above-mentioned bioreactor was monitored in order to determine its degrading capability. The concentration of some compounds (sodium malonate, manganese sulphate) from the reaction mixture was optimised in order to maximise the decolourisation levels. A percentage of Poly R-478 decolourisation of 24% after 15 min of dye incubation was achieved. On the other hand, a methodology for a long treatment of these dyes based on the continuous addition of MnP enzyme and H(2)O(2) was developed. Moreover, this enzymatic treatment was compared with a photochemical decolourisation process. The former allowed to maintain the degradation rate almost constant for a long time, resulting in a decolourisation percentage of 70% and 30% for crystal violet and Poly R-478, respectively, after 2 h of treatment. As for the latter, it was not able to degrade Poly R-478, whereas crystal violet reached a degradation of 40% in 2 h.

Enhanced ligninolytic enzyme production and degrading capability of Phanerochaete chrysosporium and Trametes versicolor

Ligninolytic enzyme production by the white-rot fungi Phanerochaete chrysosporium and Trametes versicolor precultivated with different insoluble lignocellulosic materials (grape seeds, barley bran and wood shavings) was investigated. Cultures of Phanerochaete chrysosporium precultivated with grape seeds and barley bran showed maximum lignin peroxidase (LiP) and manganese-dependent peroxidase (MnP) activities (1000 and 1232 U/l, respectively). Trametes versicolor precultivated with the same lignocellulosic residues showed the maximum laccase activity (around 250 U/l). For both fungi, the ligninolytic activities were about two-fold higher than those attained in the control cultures. In vitro decolorization of the polymeric dye Poly R-478 by the extracellular liquid obtained in the above-mentioned cultures was monitored in order to determine the respective capabilities of laccase, LiP and MnP. It is noteworthy that the degrading capability of LiP when P. chrysosporium was precultivated with barley bran gave a percentage of Poly R-478 decolorization of about 80% in 100 s, whereas control cultures showed a lower percentage, around 20%, after 2 min of the decolorization reaction.

Electrokinetic-enhanced phytoremediation of soils: Status and opportunities

Phytoremediation is a sustainable process in which green plants are used for the removal or elimination of contaminants in soils. Both organic and inorganic contaminants can be removed or degraded by growing plants by several mechanisms, namely phytoaccumulation, phytostabilization, phytodegradation, rhizofiltration and rhizodegradation. Phytoremediation has several advantages: it can be applied in situ over large areas, the cost is low, and the soil does not undergo significant damages. However, the restoration of a contaminated site by phytoremediation requires a long treatment time since the remediation depends on the growth and the biological cycles of the plant. It is only applicable for shallow depths within the reach of the roots, and the remediation efficiency largely depends on the physico-chemical properties of the soil and the bioavailability of the contaminants. The combination of phytoremediation and electrokinetics has been proposed in an attempt to avoid, in part, the limitations of phytoremediation. Basically, the coupled phytoremediation-electrokinetic technology consists of the application of a low intensity electric field to the contaminated soil in the vicinity of growing plants. The electric field may enhance the removal of the contaminants by increasing the bioavailability of the contaminants. Variables that affect the coupled technology are: the use of AC or DC current, voltage level and mode of voltage application (continuous or periodic), soil pH evolution, and the addition of facilitating agents to enhance the mobility and bioavailability of the contaminants. Several technical and practical challenges still remain that must be overcome through future research for successful application of this coupled technology at actual field sites.

Surfactant-enhanced Electrokinetic Remediation of Mixed Contamination in Low Permeability Soil

Abstract Thousands of sites are contaminated with both heavy metals and organic compounds and these sites pose a major threat to the environment. Very few technologies, such as soil washing/flushing and stabilization/solidification, are available to remediate these sites; however, all these technologies are ineffective under low permeability and heterogeneous soil conditions. Previous studies have shown that electrokinetic remediation has potential to remove heavy metals and organic compounds when they exist individually in clayey soils. In the present study, the feasibility of using surfactants in electrokinetic remediation was evaluated to remove the PAHs in the presence of heavy metals from clayey soils. Kaolin was selected as a model clayey soil and it was spiked with phenanthrene and nickel at a concentration of 500 mg/kg-dry each to simulate typical mixed contamination. Bench-scale electrokinetic tests were performed using deionized water and two different surfactants, Igepal CA-720 and Tween 80, at 3% and 5% (in weight) each at the anode. These solutions at the anode were circulated and were buffered with 0.01 M NaOH to maintain neutral pH conditions. A periodic voltage gradient of 2 V/cm (with 5 days on and 2 days off cycles) was applied for all the tests. There was a significant migration of phenanthrene towards cathode in all the tests. Among all the extracting solutions used, complete removal of phenanthrene was observed using 5% Igepal CA-720. In case of Tween 80, the low electroosmotic flow limited the delivery of Tween 80 into the soil and therefore, limiting the phenanthrene solubilization and transport. It was observed that solubilization, electroosmotic flow, and concentration of the extracting solution are the critical factors that contribute to the removal of phenanthrene. Nickel electromigrated as cation towards the cathode and precipitated in the soil near the cathode due to high pH in all tests. Overall, nickel migration pattern was not affected by the presence of phenanthrene and the extracting solutions used in this study.

Sequential Electrokinetic Remediation of Mixed Contaminants in Low Permeability Soils

The coexistence of heavy metals and polycyclic aromatic hydrocarbons (PAHs) at many of the contaminated sites poses a severe threat to public health and the environment. Very few technologies, such as soil washing/flushing and stabilization/solidification, are available to remediate such sites; however, these technologies are ineffective and expensive to treat contaminants in low permeability clayey soils. Previous studies have shown that electrokinetic remediation has potential to remove heavy metals and organic compounds when they exist individually in clayey soils. In the present study, the feasibility of using surfactants and organic acids sequentially and vice versa during electrokinetic remediation was evaluated for the removal of both heavy metals and PAHs from clayey soils. Kaolin was selected as a model clayey soil and it was spiked with phenanthrene and nickel at concentrations of 500 mg/kg dry each to simulate typical field mixed contamination. Bench-scale electrokinetic experiments were perfor...

Iron removal from kaolin. Comparison between “in situ” and “two-stage” bioleaching processes

Abstract The filamentous fungus Aspergillus niger can produce large amounts of organic acids (especially oxalic acid) which can be used for the removal of the iron contained as impurity in kaolin. This allows an increase of kaolin whiteness index, a very important factor for its industrial application. Iron leaching may be carried out “in situ” by growing A. niger on kaolin, the efficiency being largely dependent on the strain used, the medium pH and the ratio: culture medium/mass of kaolin. In addition, the presence of kaolin in growing cultures affects negatively both fungus development and active metabolite secretion. In order to overcome the drawbacks, an alternative two-stage bioleaching process was examined. Firstly, fungus was cultured in optimum conditions for active metabolite production. Then, the spent medium was used as leaching agent. Large concentrations of oxalic acid are produced in the culture stage and a kaolin 80% whiteness index is obtained after the leaching process.

Oxalic acid production by Aspergillus niger

Aspergillus niger is able to produce a quite high concentration of oxalic acid using sucrose as carbon and energy source. Operating at pH higher than 6 and an enriched N and P medium is necessary in order to conduct the fermentation towards oxalic acid production. A pH shift technique, operating at acid pH in the first two days and then setting pH to 6, allowed the productivity to slightly increase in shaking flasks cultures up to 3.0 kg/m 3 . d, with a final oxalic acid concentration of 29 kg/m 3 . When operating at more controlled conditions, in a stirred tank, both productivity and oxalic acid concentration were improved (4.1 kg/m 3 . d and 33.8 kg/m 3 , respectively). However the main drawback of this fermentation is the low yield attained (about 0.3 kg oxalic acid/kg sucrose) because most of glucose, resulting from the hydrolysis of sucrose by the extracellular enzymes secreted at the beginning of the fermentation, is very quickly oxidised to gluconic acid, a process which is favoured at a pH close to 6. Milk whey was proved to be a very good substrate as it allows oxalic acid to be produced with a similar productivity (2.5 kg/m 3 . d in shaking flasks) giving excellent yields of almost 0.6 kg oxalic acid/ kg lactose.

Manganese Removal from Spiked Kaolinitic Soil and Sludge by Electromigration

In this paper the feasibility of Mn removal from soils by electromigration is presented. Several experiments were conducted with two kind of samples (saturated and unsaturated) with the aim of understanding the behavior of Mn in a porous medium within an electric field. The unsaturated samples were prepared with properties similar to sludges, and the saturated samples had characteristics similar to a mine soil. An electric field with a constant potential difference of 15 or 30 V DC was applied across the electrokinetic cell (100 mm length, 32 mm diameter), with the sludge sample containing 3 to 5 g Mn/kg dry weight. The system was monitored for the voltage drop, current intensity, electroosmotic flow of liquid through the sample, and the pH of the electrolyte solutions. The test duration ranged from 174 to 218 hours. Metal removal in the unsaturated samples was about 78%, i.e., the Mn removed to the electrolyte solutions. However, in the saturated soils most of the Mn removed (74%) accumulated in a plain ...

Laccase production in semi-solid cultures of Phanerochaete chrysosporium

Cultures of Phanerochaete chrysosporium, operating with an inert carrier (nylon sponge) and a non-inert carrier (barley straw), were employed in order to study laccase production during semi-solid state conditions. Manganese (IV) oxide, added to the cultures increased laccase activity 16-fold especially in barley straw cultures, in which a maximum laccase activity of 360 U/l (one unit is defined as 1 μmol of 2,2‘-azino-di-[3-ethyl-benzothiazoline-(6)-sulphonicacid] oxidized per minute) was achieved.

Assessing the applicability of phytoremediation of soils with mixed organic and heavy metal contaminants

Soil pollution is a major environmental problem and many contaminated sites are tainted with a mixture of organic and heavy metal contaminants. Compared to other remedial strategies, phytoremediation is a low cost, environmentally-friendly, sustainable means of remediating the contamination. This review first provides an overview of phytoremediation studies where the soil is contaminated with just one type of pollutant (heavy metals or organics) and then critically evaluates the applicability of phytotechnologies for the remediation of contaminated sites where the soil is polluted by a mixture of organic and heavy metal contaminants. In most of the earlier research studies, mixed contamination was held to be detrimental to plant growth, yet there were instances where plant growth was more successful in soil with mixed contamination than in the soil with only individual contaminants. New effective phytoremediation strategies can be designed for remediation of co-contaminated sites using: (a) plants species especially adapted to grow in the contaminated site (hyperacumulators, local plants, transgenic plants); (b) endophytic bacteria to enhance the degradation in the rizhosphere; (c) soil amendments to increase the contaminants bioavailability [chelating agents and (bio)surfactants]; (d) soil fertilization to enhance the plant growth and microbial activity in the soil; and (e) coupling phytoremediation with other remediation technologies such as electrokinetic remediation or enhanced biodegradation in the rhizosphere.