摘要:

Using enzymes as decontaminating agents has received great attention. One of the most promising groups of enzymes, laccases, are used to decontaminate phenol-polluted systems and for bio technological applications. Higher plants and fungi, mostly wood-rotting fungi, are the main producers of laccases, but bacterial laccases also have been found. Belonging to the class of phenoloxidases, laccases catalyze the polymerization of several phenolic substances to polymeric products. In addition, they have transformed lignin and lignin-related compounds, showing a very broad substrate specificity. Specific compounds acting as protein-synthesis inducers historically have been used to improve the production of the enzyme. Recent success in fungal molecular and cellular engineering technology has contributed to significantly increase the industrial production of recombinant laccase. Kinetic (Michaelis-Menten parameters, optimum pH,kcat) and stability properties of laccases may vary according to the source of the enzymes. Laccases are used in a variety of applications, such as to remove toxic compounds from aquatic and terrestrial systems, to produce and treat beverages, as analytical tools, and as biosensors to estimate the quantity of phenols in natural juices or the presence of other enzymes. Laccases have been used successfully in immobilized form as well as dissolved in organic solvents.

ISSN:1088-9868    

DOI:10.1080/10889869991219163

出版商:TAYLOR & FRANCIS    

年代:1999

数据来源: Taylor

摘要:

The root structure of a mature 12-year-old mulberry tree growing in a former waste disposal basin and the relationship of the tree's root system to the distribution of polycyclic aromatic hydrocarbons (PAHs) in soil/sludge beneath the tree were examined. Root excavation showed that large roots were restricted to the upper 60 cm of the root zone, whereas medium-sized (0.3 to 2.5 cm) and fine (<0.3 cm) roots were present throughout the root zone reaching depths of 110 cm. Comparison of the concentrations of PAHs in the root zone with those in the sludge beneath the root zone (>2.0 m) showed dramatic differences. In the upper 60 cm of the root zone, where roots have prevailed for potentially 12 years, the PAH concentrations were approximately 10 to 20% of those in the sludge. At lower rooting depths 60 to 100 cm, where fewer roots have been present for a shorter time period, the PAH concentrations have decreased but to a lesser degree. These field results provide evidence that the mulberry root system develops gradually over time in a vertical direction with fine roots serving as the leading edge of a moving front. The degradative properties of this biological front (root-microbe combination) toward toxic chemicals hold great importance for successful development of phytoremediation technology designed to degrade deep contaminants in former sludge basins.

ISSN:1088-9868    

DOI:10.1080/10889869991219172

出版商:TAYLOR & FRANCIS    

年代:1999

数据来源: Taylor

摘要:

The role of soil, straw, and sawdust as supports in enhancing pentachlorophenol (PCP) mineralization by an indigenous soil consortium was examined by assessing the bioavailability of the substrate and other nutrients. PCP sorption tests were conducted in the presence of sterile supports to evaluate PCP bioavailability. Indigenous biomass, practically free of soil particles, was prepared to test the influence of sterile soil and soil components on the mineralization of increasing PCP concentrations. Organic supports such as straw and sawdust were very good sorbents for PCP, resulting in a slow, continuous desorption of substrate, high mineralization rates, and reduced toxicity to the active biomass. Soil and clay retained less PCP and desorbed it in decreasing amounts. Soil was the best amendment to enhance the mineralization of 100 mg/L PCP. Soil, soil extract, and the lowest-molecular-weight fraction of the soil extract facilitated the complete mineralization of 300 mg/L of PCP with a lag time of about 9 days, compared to 21 days for the unamended culture. Addition of soil enhanced PCP mineralization by an indigenous consortium, probably because soil particles served as an adsorbent for the contaminant to decrease its toxicity, as a support for biomass colonization, and as a source of supplementary nutrients for the biomass. This concept is of importance, particularly for the production of active and resistant biomass for the biotreatment of contaminated soils.

ISSN:1088-9868    

DOI:10.1080/10889869991219181

出版商:TAYLOR & FRANCIS    

年代:1999

数据来源: Taylor

摘要:

Compost windrows for bioremediation of soil were built at a wood-preserving site contaminated with chlorophenols, polychlorinated dibenzo-p-dioxins (PCDDs), and polychlorinated dibenzofurans (PCDFs). Sampling of airborne particles during the mixing of the compost windrows found concentrations of PCDDs and PCDFs in different particle sizes. The congener distribution of PCDDs and PCDFs in the collected air particle fractions was similar to that in the compost windrows, and the level of PCDDs and PCDFs was 1000-fold higher than the atmospheric background values reported previously. Viable particle-sizing samplers and several selective growth media were used to enumerate bacteria and fungi in the airborne particles. From the collected air samples, 40 bacteria were isolated and identified. Among the isolated bacteria, 80% were Gram-positive and spore-forming. Two of the identified airborne bacteria,Pseudomonas aeruginosaandBacillus cereus, may cause human disease and are classified in biological agent hazard group 2. The amounts of airborne fungi, molds, and yeasts were 1000 to 2000 colony-forming units (CFUs) per m3. The number of actinomycetes was up to 6-fold, and the number of bacteria was 2- to 20-fold compared to background values. The overall level of airborne bacteria (200 to 3500 CFUs per m3) was low compared to the level of bacteria (105to 108CFUs per m3) found when composting municipal waste.

ISSN:1088-9868    

DOI:10.1080/10889869991219190

出版商:TAYLOR & FRANCIS    

年代:1999

数据来源: Taylor

摘要:

Enhanced microbial activity and xenobiotic transformations take place in the rhizosphere. Degradation and binding of 2,4,6-trinitrotoluene (TNT) were determined in two rhizosphere soils (RS) and compared to respective unplanted control soils (CS). The rhizosphere soils were obtained after growing corn for 70 d in soils containing 2.8% (Soil A) or 5.9% (Soil B) organic matter. Aerobically agitated soil slurries (3:1, solution/soil) were prepared from RS and CS and amended with 75 mg TNT L−1(14C-labeled). TNT degraded more rapidly and formed more un-extractable bound residue in RS than in CS. In Soil A, total extractable TNT decreased from 225 to 1.0 mg kg−1in RS, whereas 11 mg kg−1remained in CS after 15 d. Unextractable bound14C residues accounted for 40% of the added14C-TNT in RS and 28% in CS. The smaller differences in Soil B were attributed partially to the higher organic matter content. The predominant TNT degradation products were monoaminodinitrotoluenes (ADNT), which accumulated and disappeared more rapidly in RS than in CS, and hydroxylaminodinitrotoluenes (HADNT). When sterilized by γ-irradiation, no significant differences between RS and CS were observed in TNT loss or bound residue formation. More rapid TNT degradation and enhanced bound residue formation in the unsterilized RS was attributed to micro-bial-facilitated production and transformation of HADNT and ADNT, which are potential precursors to bound residue formation. If plants can be established on TNT-contaminated soil, these results indicate that the rhizosphere can accelerate reductive transformation of TNT and promote bound residue formation.

ISSN:1088-9868    

DOI:10.1080/10889869991219208

出版商:TAYLOR & FRANCIS    

年代:1999

数据来源: Taylor

摘要:

The bioremediation potential of hydrocarbon-contaminated soils from the most northerly inhabited station in the world, Canadian Forces Station - Alert, was assessed. Microbial enumeration, by both viable plate counts and direct counts, combined with molecular analysis (polymerase chain reaction and colony hybridization) for hydrocarbon catabolic genes (alkB,ndoB,xylE), demonstrated the presence of significant numbers of cold-adapted hydrocarbon-degrading microorganisms. The degradative activity of these populations was assessed by mineralization of14Clabeled hexadecane (C16) at 5°C in untreated and treated soils. Although very low rates of C16 mineralization were observed in the untreated soils, nutrient supplementation with a fertilizer markedly increased C16 mineralization. Highly active cold-adapted hydrocarbon-degrading consortia were prepared from soil slurries, and their degradative potentials were monitored by biomass measurements and mineralization activity. Bio augmentation of the contaminated soils with consortia containing the greatest percentages of degradative bacteria resulted in the shortest C16 mineralization acclimation period. However, treatment with the consortia plus fertilizer did not appreciably increase C16 mineralization or reduce total petroleum hydrocarbon concentrations to a greater extent than did the fertilizer treatment alone. These results indicate that the soils possessed sufficient numbers of cold-adapted degradative bacteria, and that fertilizer application alone was sufficient to obtain elevated levels of degradative activity at low ambient summer temperatures.

ISSN:1088-9868    

DOI:10.1080/10889869991219217

出版商:TAYLOR & FRANCIS    

年代:1999

数据来源: Taylor