PCBs stimulate laccase production and activity in Pleurotus ostreatus thus promoting their removal.

Pleurotus ostreatus degrades polychlorinated biphenyls (PCBs) with an increase of laccase activity. Laccases are well known for their detoxifying activity. We show, using reverse transcription polymerase chain reaction and a biochemical assay, that reduction in PCBs (di, tri, tetra, and penta) levels are correlated with an increase in laccase activity. P. ostreatus cultures were obtained from 0 to 30 days in the presence or absence of 7,100 mg/L PCBs (from transformer oil) and a surfactant. After each selected time cultures were withdrawn and remaining PCBs were determined, a maximal removal percentage of PCBs was obtained at 20 (63.5 ± 2.0) and 30 days (63.8 ± 4.6) post-induction. Also, the activity of the enzyme was analyzed and it was found to increase at 10 (6.9-fold) and 20 (6.77-fold) days post-induction in the presence of PCBs, as determined by its activity. Taken together, these data suggest that PCBs induce laccase expression and that laccase catalyzes PCBs removal.

Fractionation and availability of heavy metals in tannery sludge-amended soil and toxicity assessment on the fully-grown Phaseolus vulgaris cultivars.

This study was conducted to assess the effect of tannery sludge on the bush bean (Phaseolus vulgaris) cultivars fully-grown on a culture sandy soil, as tannery sludge is valuable to improve soil fertility but long term studies evaluating the effect on fully grown plants are scarce. Tannery sludge amendments (0, 0.77, 1.54, 3.08 and 6.16 g tannery sludge kg(-1) soil) were characterized and the main heavy metals identified (Cr, Mn, Fe, K, and Zn) later on sequentially and singly extracted, for soil fractionation and availability determination, respectively. Metals showed different fractionation and availability patterns, being the most toxic metal (Cr) found to primarily bind to the carbonate fraction in soil, while almost 10% of the total Cr was available for plant uptake. In the green house experiments, bush bean cultivars exposed to increasing tannery sludge amendments were evaluated at different plant stages. Metal accumulation and physiological parameters (chlorophyll, carotenoids, nitrate reductase activity and dry weight) were determined. Toxicity was primarily due to Cr, stimulating or affecting the response of physiological parameters and suppressing seed formation at the highest tannery sludge ratio. Metals were mainly accumulated in the roots of bush beans, diminishing in the upper part of the plants with minimal translocation to seeds, supposing little risk for human consumption. Additionally, important correlations, antagonistic and synergistic relationships were observed between the extracted metals and metal accumulation in plant tissues.

Toxicity assessment of soil amended with tannery sludge, trivalent chromium and hexavalent chromium, using wheat, oat and sorghum plants.

This work assessed the effect of soil amended with tannery sludge (0, 500, 1000, 2000, 4000 and 8000 mg Cr kg(-1)soil), Cr(3+) as CrCl(3).6H(2)O (0, 100, 250, 500, 1000 and 2000 mg Cr kg(-1)soil), and Cr(6+) as K(2)Cr(2)O(7) (0, 25, 50, 100, 200 and 500 mg Cr kg(-1)soil) on wheat, oat and sorghum plants. Seed germination, seedling growth (root and shoot) and Cr accumulation in dry tissue were measured. Toxicological parameters; medium effective concentration, no observed adverse effect concentration and low observed adverse effect concentration were determined. Root growth was the most sensitive assessment of Cr toxicity (P<0.05). There was a significant correlation (P<0.0001) between Cr accumulation in dry tissue and toxic effects on seedling growth. The three Cr sources had different accumulation and mobility patterns; tannery sludge was less toxic for all three plant species, followed by CrCl(3).6H(2)O and K(2)Cr(2)O(7).

Labscale anoxic stabilization ponds operated under high organic loads: long term effect of enrichment with activated sludge.

The addition of acclimatized activated sludge has been suggested as an effective enrichment procedure to increase the biological activity of waste stabilization ponds. This enrichment results in higher degradation rates compared to non enriched stabilization ponds. However, the comparison between enriched and non enriched ponds has been observed during short term experiments and it is unknown if this enrichment has long-term effect. This paper compares enriched and non enriched experimental ponds over two years of continuous operation. The enriched pond showed a degradation activity constantly twice higher. The biological indicators such as the heterotrophic and facultative plate count numbers, the chlorophyll "a" concentration and the oxygen consumption rate were also constantly higher in the enriched pond. These results suggest that an initial enrichment has a long term enhancement effect on stabilization ponds treating complex wastewaters.

Effect of culture conditions on fatty acids composition of a biosurfactant produced by Candida ingens and changes of surface tension of culture media.

This work investigated the effect of culture medium composition on a biosurfactant production and their total fatty acids content, as well as the surface tension of media, and biomass production by Candida ingens. A factorial experimental design was used to evaluate the combined effect of C/P, C/N(inorganic), C/Fe, C/Mg ratios and yeast extract concentration. The highest biosurfactant production was reached when high C/Fe and high C/P ratio variables were combined; biosurfactant concentration increased by a 3.42 fold. The variable with the highest effect on net decrease surface tension (DeltaST) and fatty acids percentage of C. ingens biosurfactant was yeast extract. The average of DeltaST (25 mN/m) and fatty acids percentage (34.7%) values were enhanced at high yeast extract concentration of 1g/l. The main conclusion of this study was that the culture composition affected the biosurfactant production by C. ingens. It was also observed that the surface tension and total fatty acids of the biosurfactant were modified as the media composition changed.

Effects of mixing low amounts of orange peel (Citrus reticulata) with hydrocarbon-contaminated soil in solid culture to promote remediation.

The effect of mixing low amounts of orange peel (Citrus reticulata) with a soil contaminated with hydrocarbons (58,000 mg kg(-1) soil) for promoting the soil remediation in solid culture was studied. The experimental design was established in solid culture at soil/orange (Citrus reticulata) peel ratios of 100:0, 98:2, 96:4, 94:6 and 92:8, at 30% humidity and a C:N:P ratio of 100:10:1, for 15, 60 and 90 days, respectively. The total petroleum hydrocarbons (TPHs) decreased significantly (69%) after 15 days in the treatment with a soil to orange peel ratio of 92:8. Furthermore, in this treatment bacterial counts increased from 17 to 20 ln CFU (2.6 x 10(6) to 5 x 10(8)), while the fungal count was 11 ln CFU (6.5 x 10(4)) at initial and final time of treatment. An increase in microbial respiration activity and TPH removal (69%) was observed at other soil/orange peel ratios after 60 days when moisture content and nutrients were adjusted; however, N and P were not consumed at a great extent.

Selection and identification of fungi isolated from sugarcane bagasse and their application for phenanthrene removal from soil.

This work investigated the identification and selection of fungi isolated from sugarcane bagasse and their application for phenanthrene (Phe) removal from soil. Fungi were identified by PCR amplification of ITS regions as Aspergillus terrus, Aspergillus fumigatus and Aspergillus niger, Penicillium glabrum and Cladosporium cladosporioides. A primary selection of fungi was accomplished in plate, considering Phe tolerance of every strain in two different media: potato dextrose agar (PDA) and mineral medium (MM). The radial extension rate (r(r)) in PDA exhibited significant differences (p<0.05) at 200 and 400 ppm of Phe. A secondary selection of A. niger, C. cladosporoides, and P. glabrum sp. was achieved based on their tolerance to 200, 400, 600 and 800 ppm of Phe, in solid culture at a sugarcane bagasse/contaminated soil ratio of 95:5, in Toyamas, Czapeck and Wunder media. Under these conditions, a maximum (70%) Phe removal by A. niger was obtained. In addition C. cladosporioides and A. niger were able to remove high (800 ppm) Phe concentrations.

Benzo[a]pyrene removal from soil by Phanerochaete chrysosporium grown on sugarcane bagasse and pine sawdust.

The capacity of Phanerochaete chrysosporium grown on soil with added sugarcane baggase (BP) and pine sawdust (PS) to remove benzo(a)pyrene (BaP) was studied. A half factorial two-level experiment 2(4-1) was designed to determine the effect of: type of lignocellulosic material (BP and PS) for fungus growth, age of fungus (5 and 10d), amount of lignocellulosic material (10% and 15% w/w) and soil moisture content (water holding capacity of 45% and 56% w/w). Inoculum obtained at different ages showed that the capacity of P. chrysosporium to remove BaP depends on the lignocellulosic used and on inoculum age. Abiotic BaP removal was affected significantly (p<0.05) by inoculum age, type of lignocellulosic added and soil moisture content. The removal of BaP by lignocellulosic material was more effective by young inocula (71.97 mg BaP kg(-1) dry soil), with high percentage of added lignocellulosic (71.57 mg BaP kg(-1) dry soil) and at low soil moisture content (73.07 mg BaP kg(-1) dry soil). When fungus was grown on BP, maximum BaP removal rate was obtained at 5d of incubation (10.85 mg BaP d(-1)l(-1) and 50.12 mg BaP kg(-1) dry soil), while in PS maximum BaP removal was obtained at 10d of incubation (12.06 mg BaP d(-1)l(-1) and 39.94 mg BaP kg(-1) dry soil).

Effect of combined nutrients on biosurfactant produced by Pseudomonas putida.

This work investigated biosurfactant production by Pseudomonas putida in combined C/P, C/Ninorganic, C/Fe, C/Mg nutrient ratios and peptone concentration. Analysis of the 2(5-1) fractional factorial experimental design showed that only the C/Fe ratio had a significant (p<0.02) effect on biosurfactant production. The highest amount of biosurfactant was obtained at low C/Fe ratios, but net surface tension did not show significant differences. In addition, low amounts of peptone and the C/P-C/Mg nutrient ratios interaction significantly (p < 0.05) enhanced the biomass produced by P. putida. Analysis of biosurfactant by gas chromatography (GC) showed that the hydrophilic fraction was composed by rhamnose and the hydrophobic fraction, mainly by palmitic (C16), stearic (C18:0), oleic (C18:1) and linoleic (C18:2) fatty acids.

Integrated biological treatment of recalcitrant effluents from pulp mills.

This work aimed at determining the degree of depuration of a recalcitrant effluent (weak black liquor, WBL) achieved in a series treatment consisting of a first stage methanogenic fluidised bed reactor followed by a second stage aerobic, upflow reactor packed with "biocubes" of Trametes versicolor immobilised onto small cubes of holm oak wood. The mesophilic, lab scale methanogenic fluidised bed reactor contained a microbial consortium immobilised onto granular activated carbon 500 microm average size. The process removed decreasing amounts of organic matter at decreasing hydraulic retention times (HRT), eventually reaching an average of 50% at 0.5 day HRT. Colour and ligninoid removals also decreased with decreasing HRT. Although the methanogenic fluidised bed reactor provided an effective treatment for the degradable organic matter, important concentrations of recalcitrant organic matter and colour still remained in the anaerobic effluent. This anaerobic effluent was fed to the aerobic packed bed reactor. Two HRT were tested in this unit, namely 5 and 2.5 days. The reactor averaged an organic matter removal in the range of 32% COD basis, during an experimental run of 95 days. Colour and ligninoid contents were removed in high percentages (69% and 54%, respectively). There was no significant difference in reactor performance at 5- and 2.5-day HRT. There was a positive correlation between pollutant removal efficiencies and Laccase activity in crude extracts of the reactor liquor. No supplemental soluble carbohydrate was required to sustain the fungus activity and the consistent reactor performance. Overall, the two-stage treatment achieved approximately a 78% removal of the original organic matter of the WBL (COD basis) and ca. 75% of colour and ligninoid contents.

Heavy metals removal by the microalga Scenedesmus incrassatulus in continuous cultures.

The microalga Scenedesmus incrassatulus was grown under continuous regime in the presence of chromium(VI), cadmium(II) and copper(II), as single metal species and as mixtures of two or three metals, in a laboratory scale system. We used an artificial wastewater with low free ion activities (as determined by MINEQL+) due to the presence of EDTA (a strong chelating agent) but with total concentrations not suitable for acceptable environments. Chromium(VI) and cadmium(II) had positive interaction that increased the removal percentages of both these metals; we could not, however, detect any interaction with copper(II). S. incrassatulus was able to remove all the tested metals to some extent (25-78%), but bivalent metals were not removed as efficiently as reported in batch cultures, probably due to the high pH values there recorded. Chromium(VI) was more efficiently removed in continuous cultures than in batch culture, because the uptake of chromate could be favored by actively growing algae.

Biostimulation of micro-organisms from sugarcane bagasse pith for the removal of weathered hydrocarbon from soil.

AIMS: In this study we studied the biostimulation of micro-organisms associated with sugarcane bagasse pith for the removal of total petroleum hydrocarbon from a soil contaminated with weathered hydrocarbon. METHODS AND RESULTS: Carbon, nitrogen and phosphorus were added at a ratio of 100 : 10 : 1, water content of 40%, and soil : bagasse ratio of 49 : 1. A significant positive difference (P < 0.05) was observed in total petroleum hydrocarbon removal (38 and 48%) by micro-organisms associated with bagasse and native soil micro-organisms, respectively. In addition, total petroleum hydrocarbon removal increased to 60% in a system where both autochthonous soil and bagasse micro-organisms were present. CONCLUSIONS: Micro-organisms from sugarcane bagasse pith can be stimulated for removal of weathered hydrocarbon from contaminated tropical soils, without they being inhibited by indigenous soil micro-organisms. SIGNIFICANCE AND IMPACT OF THE STUDY: Soil of with hydrocarbons can be diminished by stimulation of autochthonous microflora present in soil and agricultural residues. This work contributes to the microbiology of composting, as low amounts of bulking agents for hydrocarbon removal from soil, can be used.

The effect of the supplementation with a primary carbon source on the resistance to oxygen exposure of methanogenic sludge.

Anaerobic methanogenic consortia have a considerable resistance to oxygen exposure. Yet, most research has been focused on the study of the tolerance to oxygen of anaerobic immobilized biomass. Less is known on the potential of the anaerobic suspended biomass for withstanding exposure to oxygen and the effect of a primary degradable substrate on such resistance. Thus, the objective of this work was to determine the effect of the amount of a primary degradable substrate (sucrose) on the resistance of a methanogenic suspended biomass to oxygen exposure. It was found that the inhibition of disperse anaerobic sludge by oxygen exposure decreases when the concentration of the supplemented carbon source increases. This is in agreement with the fact that aerobic respiration of the added substrate by the facultative heterotrophic bacteria, always present in this type of sludge, has been found in previous studies as one of the main mechanisms protecting methanogens against O2. From a practical point of view, this suggests that aeration of anaerobic systems should be possible without inhibiting the activity of methanogenic bacteria if an adequate ratio between oxygen and COD feeding is maintained. Such a ratio will depend however on the wastewater initial COD concentration.

Phenol removal in upgraded facultative waste stabilisation ponds.

Treatment of wastewater containing phenol using laboratory scale waste stabilisation ponds enriched with activated sludge was studied. After enrichment, the efficiency of these ponds under high phenol loading rates (i.e. up to 408 kg phenol ha(-1) day(-1)) was studied. At phenol loading rates of 6, 52, 312, 636 and 972 COD ha(-1) day(-1), the phenol removal efficiencies were 77, 69, 76, 59 and 52%, respectively. The results suggest that enrichment is an effective potential method to increase the removal capability of facultative ponds, not only or easily biodegradable compounds but also for xenobiotics.

Removal of phenanthrene from soil by co-cultures of bacteria and fungi pregrown on sugarcane bagasse pith.

Sixteen co-cultures composed of four bacteria and four fungi grown on sugarcane bagasse pith were tested for phenanthrene degradation in soil. The four bacteria were identified as Pseudomonas aeruginose, Ralstonia pickettii, Pseudomonas sp. and Pseudomonas cepacea. The four fungi were identified as: Penicillium sp., Trichoderma viride, Alternaria tenuis and Aspergillus terrus that were previously isolated from different hydrocarbon-contaminated soils. Fungi had a statistically significant positive (0.0001

Isolation and characterization of bacteria degrading polychlorinated biphenyls from transformer oil.

Polychlorinated biphenyls from transformer oil were degraded in liquid culture under aerobic conditions using a mixed bacterial culture isolated from a transformer oil sample with a high content of polychlorinated biphenyls and other hydrocarbons. Four strains were identified, three of them corresponded to genus Bacillus, the other one to Erwinia. Bacteria in the transformer oil could remove as much as 65% of polychlorinated biphenyls (88% W/V in the transformer oil). Additional data showed that the two isolated strains of B. lentus were able to grow on transformer oil and degrade polychlorinated biphenyls by 80 and 83%. Our results provide evidence that microorganisms occurring in transformer oil have the potential to degrade polychlorinated biphenyls.