Overcoming the inhibition effects of metal ions in the degradation of benzene and toluene byalcaligenes xylosoxidans y234

The effects of metal ions on the biodegradation of benzene and toluene were investigated. Among 12 tested metal ions, Cu²⁺, Ni²⁺, Co²⁺ and A⁺ _g inhibited the degradation of benzene and toluene severely byAlcaligenes xylosaxidans Y234. Cu²⁺ was found to inhibit catechol 1,2-dioxygenase in the degradation of benzene and toluene. Co²⁺ and Ni²⁺ were supposed to inhibit benzoate 1,2-dioxygenase, while Ag⁺ was supposed to inhibit benzaldehyde dehydrogenase in the degradation of toluene. The inhibition effect caused by these metal ions could be overcome both by microbial adaptation and by adding specific aromatic compounds to the broth.     

Biodegradation of aromatic compounds in a self-cycling fermenter (SCF)

The Self-cycling fermentation (SCF) technique was applied to the biodegradation of several aromatic compounds by Pseudomonas putida and Pseudomonas fluorescens. The SCF technique was shown to have several advantages over the sequential batch reactor and other methods of biodegradation. The SCF technique allowed stable and repeatable performance over an extended period of time, with almost complete substrate consumption. The system was flexible and easily adapted to changes in concentration and/or type of substrate. The rates of consumption were considerably higher than reported for any other biodegradation technique.     

Effects of strontium doping on the degradation and Sr ion release behaviors of α‐tricalcium phosphate bone cement

Strontium plays important physicochemical and biological roles in the applications of bone repair materials. The available methods of Sr doping in bone cements were believed to make a key effect on the biodegradation and Sr ion release behaviors of cements. In this work, Sr‐doped octacalcium phosphate (Sr‐OCP), Sr‐doped α‐tricalcium phosphate (Sr‐α‐TCP), SrCO₃, and SrCl₂ with different actual availability of Sr²⁺ were imported into α‐TCP bone cements, and their effects on the biodegradation and ions release of cements were comparatively investigated. Incorporation of different Sr carriers had led to distinct hydration morphologies, crystal evolutions, degradation rates, and microenvironments of bone cements during their in vitro biodegradation. Compared with other Sr carriers, Sr‐OCP facilitated the hydration reaction of α‐TCP, which induced the enhanced degradation and Sr ion release behaviors. In conclusion, Sr‐OCP was supposed to be a more potential Sr carrier applied in the synthesis of biodegradable Sr‐doped calcium phosphate bone cements.     

Reaction Engineering Studies on the Biodegradation of Anthracene on Bioremediation of Diesel Contaminated Soil Using Acinetobacter sp. (ATCC No. 14293)

In the present investigation bio‐degradation of anthracene, a polyaromatic hydrocarbon, from its simulated mixture in methanol, has been studied using a monoculture strain, (Acinetobacter sp. (ATCC No. 14293)), within the concentration range 500‐800 mg/dm³. In a separate attempt bioremediation of diesel contaminated soil to reduce total aromatic content using the same bacterial strain has been carried out. The main emphasis of this investigation is to understand the complex reaction engineering behaviour involved in both the above bioprocess systems. It is observed that while Monod's classical substrate uninhibited model can be used for simulation purpose for the biodegradation of anthracene, the reaction engineering behaviour of the bioremediation of soil can be expressed by coupling Monod's classical equation with first order cell decay rate. In both the cases the concerned intrinsic kinetic parameters have been evaluated.     

Characterization of coating systems by scanning electrochemical microscopy: Surface topology and blistering

Operation of the scanning electrochemical microscope used in feedback mode over a coated metal allows changes in the state of the coating surface to be monitored during immersion in aqueous electrolytes. This paper reports changes in the coating induced by specific anions in the electrolyte in situ during immersion. Significant surface roughening is observed for immersion times shorter than 1 day when the electrolyte contains chloride ions. This effect is also observed when the oxygen dissolved in the electrolytic phase is employed as redox mediator for SECM imaging. The coated system exposed to chloride-free electrolytes containing sulphate or nitrate maintains a featureless topography within the same time scale. The observed features are due to the nucleation and growth of blisters at the metal/coating interface induced by chloride ions in the environment. The implication is that ionic migration occurs simultaneously with the absorption of water by the coating already from the beginning of exposure to the aqueous environment. The unique role of chloride ions compared with sulphate or nitrate ions towards coating performance has been established at a very early stage following immersion of the sample.     

Biodegradation Capability and Enzymatic Variation of Potentially Hazardous Polycyclic Aromatic Hydrocarbons—Anthracene and Pyrene by Anabaena fertilissima

This study encompasses the biodegradation capacity of Anabaena fertilissima to model PAH (Polycyclic Aromatic Hydrocarbon) compounds namely Anthracene (ANT) and Pyrene (PYR) at different LC₅₀ concentrations viz., 5.0 mg/L and 3.0 mg/L, respectively, on growth in terms of Chlorophyll-a and protein. Depletion in chlorophyll-a and protein content was registered with rise in PAHs concentration while the inhibition of nitrogen fixing enzymes such as nitrate reductase and glutamine synthetase activity was also concentration dependent and showed more sensitivity for high molecular weight aromatic compound PYR as compared to ANT. GC/MS analysis explained the degradation of ANT by 46% and PYR by 33%, at 5.0 mg/L and 3.0 mg/L, respectively. Moreover, the common degraded product for ANT was 2, 4-Dimethyl-1-heptene and for PYR it was 2, 3, 4-Trimethylhexane. Results indicate that PYR was more stable and recalcitrant compared to ANT. This study suggests that Anabaena fertilissima could be used for bioremediation of ANT and PYR pollution in surface waters and terrestrial environments.     

BTEX removal from contaminated groundwater by a co‐culture of Pseudomonas putida and Pseudomonas fluorescens immobilized in a continuous fibrous‐bed bioreactor

A fibrous‐bed bioreactor with immobilized cells of Pseudomonas putida and Pseudomonas fluorescens was used to treat groundwater contaminated with benzene, toluene, ethylbenzene, and xylenes (collectively know as BTEX). The kinetics of BTEX biodegradation in the fibrous‐bed bioreactor operated under continuous well‐mixed conditions was studied at room temperature. Aeration was not used in the process fed with groundwater samples with an average total BTEX concentration of 2.75 mg dm^?3. All BTEX compounds present in the groundwater feed were concurrently and completely biodegraded even under oxygen‐limited or hypoxic conditions. Nearly 100% removal efficiency was obtained when the retention time was greater than 1 h. BTEX removal efficiency decreased with decreasing the retention time, with p‐ and o‐xylenes showed up first in the treated groundwater, followed by benzene and then other BTEX compounds. Biodegradation rates of BTEX generally increased with increasing BTEX concentration and loading rate. The maximum BTEX biodegradation rate was 5.76 mg h^?1 dm^?3 at the loading rate of 6.54 mg dm^?3 h^?1. The bioreactor had a stable performance, maintaining its ability for efficient BTEX degradation without requiring additional nutrients for more than 1 month. The good performance of the fibrous‐bed bioreactor was attributed to the high cell density (～15 g dm^?3 reactor volume) in the fibrous matrix. © 2002 Society of Chemical Industry     

新筛选菌种Delftia sp.XYJ5生物降解苯胺的途径

A promising gram-negative bacterial strain for the biodegradation of aniline as the sole carbon, nitrogen and energy sources was successfully isolated and identified as Delftia sp. XYJ6. The optimal temperature and pH for both the growth of Delftia sp. XYJ6 and the biodegradation of aniline were 30°C and 7.0, respectively. Initial aniline of 2000 mg•L－1 could be completely removed by the strain at 22 h, which showed that Delftia sp. XYJ6 had a strong ability in the biodegradation of aniline. It indicated that aniline was firstly converted to catechol catalyzed by aniline dioxygenase as a first product, which was then further biodegraded to cis,cis-muconic acid catalyzed by the catechol 1,2-dioxygenase of Delftia sp. XYJ6 as a second product. Cis,cis-muconic acid could also be further biodegraded to other small compound again. The pathway for the biodegradation of aniline by Delftia sp. XYJ6 was not previously reported.     

catA Gene in a Potential Corynebacterium Strain is Responsible for its Efficiency in Phenol Bioremoval

Out of 10 bacterial strains isolated out of wastewater of a pharmaceutical industry the most efficient bacterium, which could tolerate 5,000 mgl^?1 of phenol in the minimal medium, was identified to be Corynebacterium sp.DST1 through 16S rDNA analysis. This strain could remove 99.4% of phenol from the minimal medium containing 4,000 mgl^?1 of phenol. The ortho catalytic pathway using the enzyme catechol 1, 2- dioxygenase was found to be the major pathway for phenol degradation in the bacterium. The gene for catechol 1, 2-dioxygenase (catA) could also be amplified using degenerate primers. Corynebacterium sp.DST1 cells were attached to sawdust and removal of phenol from industrial effluents was evaluated. About 92.7% of phenol could be removed from the effluent of a heavy electrical industry. The results of this study not only suggest the potentiality of the strain to remove phenol efficiently from crude industrial effluents but also display a cheap method of bioremediation using sawdust.     

Studies on Thorium Phosphate Ion Exchanger. Part III. Paper Chromatographic Behavior and Separations of Metal Ions on Thorium Phosphate Papers

Abstract

Thorium phosphate papers have been prepared by treatment with thorium nitrate and phosphoric acid solutions. Several metal ions have been chromatographed on thorium phosphate paper. The effect of pH on R_F values has been investigated. Some useful analytical separations of metal ions have been achieved by using only dilute mineral acid and a mixed solvent system.     

Biodegradation of diesel oil in a baffled roller bioreactor

BACKGROUND: Ex situ bioremediation is a feasible and economical way to remove petroleum pollutants from contaminated soil or water. A baffled roller bioreactor was shown to be effective for biodegradation of diesel oil as a model petroleum pollutant. Microorganisms enriched from an industrially contaminated soil with heavy hydrocarbons were shown to be the best inoculum source for diesel biodegradation. RESULTS: The baffled roller bioreactor demonstrated better performance than control (roller bioreactor without baffles) or bead mill roller (control bioreactor filled partially with spherical beads) bioreactors. Biodegradation consisted of both fast and slow stages for degradation of light and heavy compounds, respectively. Among the tested temperatures ranging from 15 to 35 °C, room temperature (23 °C) was found to be the optimum temperature for biodegradation. The values of maximum specific growth rate and substrate yield (µ_max and Y_XS) for the indigenous microorganisms in the baffled roller bioreactor at room temperature were found to be 0.72 ± 0.08 h^?1 and (7.0 ± 1.0) × 10⁷ cells mg^?1 diesel, respectively. Biodegradation of diesel concentrations up to 200 g L^?1 was achieved with the highest biodegradation rate of 266 mg L^?1 h^?1 at the highest rotation rate of 45 rpm in the baffled roller bioreactor. CONCLUSION: Using indigenous bacteria enriched from industrial contaminated soil at room temperature, a baffled roller bioreactor is able to biodegrade high diesel oil concentrations at high biodegradation rates. Copyright © 2008 Society of Chemical Industry     

Analysis of microbial adaptation at enzyme level for enhancing biodegradation rate of BTX

Catechol was found to be a common intermediate in the degradation of benzene and toluene byAlcaligenes xyhsoxidans Y234, and the ring cleavage of the catechol mediated by catechol 1,2-dioxygenase was a rate-determining step. Since benzene induced higher level of catechol 1,2-dioxygenase than toluene, the cells pre-adapted to benzene showed higher degradation rate of benzene and toluene. The degradation rate ofm-xylene was also increased significantly when benzene-adapted cells were inoculated.m-Xylene was metabolized via 3-methyl catechol which was effectively cleaved by catechol 1,2-dioxygenase.     

Comparison of NO adsorbing ability and process on Pt/Mg/Al oxide catalysts prepared by different methods

Pt/Mg/Al metal oxide catalysts were prepared by impregnation and co-precipitation methods, respectively. These samples were characterized by BET, XRD and NO-TPD; their NO _X storage property and adsorbing intermediate species were investigated with NSC and FTIR. The results showed that the prepared methods exert significant influence on the physical structure properties and the adsorption abilities of NO. (Pt)/Mg/Al samples prepared by impregnation (IM) have larger specific areas and higher NO _X storage capacity than (Pt)/Mg/Al catalysts prepared by co-precipitation (CP). The intermediate species of NO adsorbing process indicated that NO was firstly adsorbed as bridged nitrites both on Pt/Mg/Al (IM) and on Pt/Mg/Al (CP), then on Pt/Mg/Al (IM) the nitrites transferred into monodentate and bidentate nitrate species while on Pt/Mg/Al (CP) the nitrites only transferred into monodentate nitrate species.     

Biodegradation of phenol at high concentration by a novel bacterium: Gulosibacter sp. YZ4

BACKGROUND: A novel bacterial strain, Gulosibacter sp. YZ4, has been isolated from activated sludge. Its application potential for phenol biodegradation has not yet been reported, therefore, in this study, biodegradation tests using strain YZ4 were executed under different conditions. RESULTS: The strain was identified as a new member of the genus Gulosibacter and nominated as Gulosibacter sp. YZ4. Phenol biodegradation tests showed that strain YZ4 could thoroughly biodegrade 1000 mg L^?1 phenol across a wide temperature range from 10 to 42 °C and pH range 5 to 11. Degradation of 1000 mg L^?1 phenol was not inhibited by the coexistence of p‐cresol or quinoline. During phenol degradation, strain YZ4 excreted both phenol hydroxylase and catechol 1,2‐dioxygenase to efficiently metabolize phenol. At 36 °C, pH 7.5, strain YZ4 could effectively degrade phenol at concentrations as high as 2000 mg L^?1 within 76 h. Haldane's model with the parameters obtained from the experiments could successfully describe the behavior of the phenol biodegradation by the strain YZ4. CONCLUSIONS: The strain YZ4 has a high potential for applications in phenol wastewater treatment in view of its adaptability to temperature and pH fluctuations and great tolerance to other coexistent toxics. Copyright © 2011 Society of Chemical Industry     

Surface tension as a limiting factor for aerobic n-alkane biodegradation

A new mathematical model for n-alkane biodegradation in crude oil, heavy oil and paraffinic mixtures is described. The pattern of n-alkane degradation as a function of the inverse of hydrocarbon chain length reported in this paper can be considered as general behaviour for many aerobic n-alkane biodegradation processes. A new interpretation of n-alkane biodegradation as a function of surface tension, is given. A mathematical expression was obtained starting from the degradation values of n-alkane and relative surface tension, which is a parameter independent of fermentation conditions. An interesting parameter, b, was identified which represented the accelerating conversion factor for n-alkane biodegradation. The findings suggested that the n-alkane biodegradation. The findings suggested that he n-alkane biodegradation rate may be affected by the fermentation condition (agitation, aeration, etc.) and by the strain of microorganism, while the behaviour pattern of n-alkane degradation was essentially linked to the substrate characteristics (molecular structure, molecular weight and density).     

Biodegradation of High Molecular Weight Polycyclic Aromatic Hydrocarbons Mixture by a Newly Isolated Fusarium sp. and Co-Metabolic Degradation with Starch

One native fungal strain, designated ZH-H2, was isolated from an agricultural soil contaminated by HMW-PAHs in a typical coal mining area of Hebei, China. The filamentous fungus was identified as a Fusarium sp. ZH-H2 was able to survive not only in the presence of the individual HMW-PAHs of Chry, BaA, B(K)F, BaP, DB(a,h)A, InP, InP and B(g,h,i)p but in the presence of a mixture of the above seven HMW-PAHs with a total concentration of up to 10 mg L^?1. Biodegradation experiments demonstrated that Fusarium sp. (ZH-H2) was able to degrade the aforementioned individual HMW-PAHs, with a degradation percentage of 77%, 85%, 91%, 42%, 56%, 42% and 38%, respectively, and degrade the aforementioned seven PAHs mixture with a degradation percentage of 48%. The effect of starch addition on the biodegradation efficiency of the PAH mixture was also investigated. The results showed a significant improvement in the degradation extent of the PAH mixture with the increase of starch concentration. The greatest degradation rate (DR; 89%) in 7 d was obtained when starch was added at 1.0 g L^?1, about 2-fold than was achieved without starch. This study implicates that Fusarium sp. (ZH-H2), a potential biodegrader, is suitable for practical field application in effective bioremediation of soils that have been simultaneously contaminated by several HMW-PAHs for a long time.     

Preparation of gelatinous aluminium hydroxide by urea from aqueous solutions containing chloride,nitrate and sulphate of aluminium

The preparation of gelatinous aluminium hydroxide from aqueous solutions containing a mixture of the chloride, nitrate or sulphate of aluminium and urea by heating at 95°C has been investigated under different conditions. The pH value of aqueous solutions, on heating for a given period of time, gradually increases, rises steeply at pH 4.0–7.5 and finally approaches a constant value. The precipitate appears at about pH 7 in the presence of chloride or nitrate ions and about pH 4 in the presence of sulphate ions. Although the gelatinous precipitates in the chloride and nitrate systems are apparently different from the granular, filterable one in the sulphate system, their compositions are not influenced by the species of aluminium salt. The fresh precipitates exist in an amorphous state, and go to pseudoboehmite by ageing. It seems that the amount of pseudoboehmite increases as the concentration of aluminium salt in aqueous solution decreases. However, the transformation from amorphous aluminium hydroxide to pseudoboehmite is reduced in the presence of sulphate ions. Furthermore, it is found that the X-ray diffraction peak for the (200) plane, as an orthorhombic structure, in the pseudoboehmite precipitated from chloride or nitrate solution is more intense than that from sulphate solution.     

Degradation of cellulosic and hemicellulosic substrates using a chelator‐mediated Fenton reaction

The involvement of catechol and hydroxamate chelators, along with hydrogen peroxide and Fe³⁺, in the degradation of cellulosic and hemicellulosic substrates was examined with the purpose of improving our current knowledge of the non‐enzymatic mechanisms involved in wood biodegradation by fungi. It could be demonstrated that a catechol chelator‐mediated Fenton reaction not only clearly degraded hemicellulosic substrates but also significantly accelerated and increased the effectiveness of degradation reactions. On the other hand, when a hydroxamate chelator‐mediated Fenton reaction was used, an inhibitory effect was observed. When cellulosic substrates underwent a chelator‐mediated Fenton reaction, no significant difference in degradation was observed between catechol and hydroxamate chelator‐mediated reactions. However, a catechol‐mediated reaction did accelerate the degradation of cellulosic substrates at the beginning of reactions. In addition, it was observed that with a chelator‐mediated Fenton reaction, oxidation of cellulose proceeds depolymerization. Copyright © 2005 Society of Chemical Industry     

Merits and limitations of TiO<Subscript>2</Subscript>-based photocatalytic pretreatment of soils impacted by crude oil for expediting bioremediation

Heavy hydrocarbons (HHCs) in soils impacted by crude oil spills are generally recalcitrant to biodegradation due to their low bioavailability and complex chemical structure. In this study, soils were pretreated with varying concentrations of ultraviolet radiation A (UVA) or ultraviolet radiation C (UVC) activated titanium dioxide (TiO₂) (1%–5%) under varying moisture conditions (0%–300% water holding capacity (WHC)) to enhance biodegradation of HCCs and shorten remediation timeframes. We demonstrate that pretreatment of impacted soils with UVC-activated TiO₂ in soil slurries could enhance bioremediation of HHCs. Total petroleum hydrocarbon (TPH) removal after 24 h exposure to UVC (254 nm and 4.8 mW/cm²) was (19.1 ± 1.6)% in slurries with 300% WHC and 5 wt-% TiO₂. TPH removal was non-selective in the C15-C36 range and increased with moisture content and TiO₂ concentration. In a 10-d bioremediation test, TPH removal in treated soil increased to (26.0 ± 0.9)%, compared to (15.4 ± 0.8)% for controls without photocatalytic pre-treatment. Enhanced biodegradation was also confirmed by respirometry. This suggests that addition of UVC-activated TiO₂ to soil slurries can transform recalcitrant hydrocarbons into more bioavailable and biodegradable byproducts and increase the rate of subsequent biodegradation. However, similar results were not observed for soils pretreated with UVA activated TiO₂. This suggests that activation of TiO₂ by sunlight and direct addition of TiO₂ to unsaturated soils within landfarming setting may not be a feasible approach. Nevertheless, less than 1% of UVA (7.5 mW/cm²) or UVC (1.4 mW/cm²) penetrated beyond 0.3 cm soil depth, indicating that limited light penetration through soil would hinder the ability of TiO₂ to enhance soil bioremediation under land farming conditions.

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Bioattenuation of Detergent Plant Effluents Enhanced via Single Microbial Augmentations

Due to natural attenuation, anionic detergents in surface waters are not inferred as big environmental issues. However, the effluents from large industrial areas with high detergent concentrations can have significant local impacts. These circumstances can be diminished by using efficient detergent‐degrading bacterial isolates through bioaugmentation. In this study, detergent plant effluents were analysed by using a methylene blue active substance assay to determine detergent content during natural attenuation processes, and after single augmentations of 12 anionic detergent‐degrading bacterial isolates with high detergent tolerating abilities in batch microcosms. Maximum bioattenuation of detergents was determined as 56 % after 66 h incubation under the conditions that mimicked the natural environment. Bioattenuation was enhanced as much as 83 and 91 % in 78 h incubation time through single microbial augmentations of filter‐sterilized and non‐sterilized effluents, respectively. Eight Pseudomonas and one Aeromonas species were found to be highly competitive by showing high biodegradation abilities in pure culture experiments as well as enhancing degradation of detergents in both filter‐sterilized and non‐sterilized effluents through their single augmentations. Although remaining three isolates, namely Pseudomonas fluorescens SDS6, P. resinovorans SDS10‐2, and P. corrugata SDS10‐3 displayed lower degrading abilities in pure culture experiments than the natural attenuation, they later turned out to be actively enhancing the degradation of detergents during their single augmentations.