Polycarbonate biodegradation by isolated molds using clear-zone and atomic force microscopic methods

The accumulation of dry waste containing synthetic polymers due to their resistance to microorganisms and other environmental factors has posed some serious problems to the environment in recent years. On the other hand, plastics constitute the foundations of economy as they are widely used in agriculture, constructions, packaging, health care and also medicine. The aim of this research was to investigate the role of different isolated fungi in the degradation of polycarbonate polymers. For this purpose, sampling was done using the garden soil and waste leachate from Isfahan Waste Management Organization. Samples were enriched in the liquid mineral salt medium supplemented with polycarbonate and then were transferred to the same medium solidified with agar to isolate and identify different fungi. Finally, their biodegradation activity was investigated with the help of clear-zone and atomic force microscopic (AFM) techniques, and also lipase and amylase production was tested. Among 15 isolated genera of mold fungi, Fusarium, Ulocladium, Chrysosporium and Penicillium showed biodegradation activity. According to the diameter of clear zone around the fungal colonies and also AFM results, the highest rate of degradation was related to Fusarium. Lipase activity of all isolated fungi was positive, but amylase activity of Ulocladium was negative. It can be concluded that some fungal strains such as Fusarium can be used for the biodegradation of plastic materials as it leads to a very eco-friendly biodegradation process.     

Isolation of <Emphasis Type="Italic">Bacillus cereus</Emphasis> from botanical soil and subsequent biodegradation of waste engine oil

Waste engine oil causes a vital environmental pollution when it spill during change and transportation and products of waste engine oil causes lethal effects to the living systems. Thus, abiotic and biotic approaches are being extensively used for removal of waste engine oil pollution. Therefore in present study, waste engine oil degradation was accomplished by a new bacterial culture, isolated from the soil by an enrichment technique. Morphological, biochemical and gene sequence analysis revealed that isolate was Bacillus cereus. Subsequently, biodegradation potential of B. cereus for waste engine oil was studied. Experimental variables, such as pH, substrate concentration, inoculum size, temperature and time on the biodegradation, were checked in mineral salt medium. The biodegradation efficiency of B. cereus was determined by gravimetry, UV–visible spectrophotometry and gas chromatography. In addition, waste engine oil was also characterized by GC–MS and FTIR for its major constituents, which showed total 38 components in waste engine oil, including hopanes, benzopyrene, long-chain aliphatic hydrocarbons, dibenzothiophenes, biphenyl and their derivatives. Results of successive biodegradation indicated that B. cereus was capable to degrade 1% of waste engine oil with 98.6% degradation potential at pH 7 within 20 days. Hence, B. cereus presents an innovative tool for removing the engine oil from the contaminated area.     

Treatment of diesel-polluted clay soil employing combined biostimulation in microcosms

The efficiency of inorganic fertilizers as stimulating agents for the bioremediation of oil-polluted environments can be increased with the addition of selected biostimulating compounds. In this study, the efficacy of different biostimulation treatments in the remediation of diesel-polluted soil in purpose-built microcosms has been evaluated. The treatments involved combinations of inorganic fertilizer with (a) Ivey surfactant, (b) Biorem organic fertilizer and (c) ethanol. Microbial activity was evaluated by monitoring the growth of heterotrophic and degrading bacteria and their dehydrogenase activity and carbon dioxide production. Hydrocarbon degradation was monitored by gas chromatography/mass spectrometry. The results showed that all treatments enhanced microbial activity in comparison with natural attenuation and also that the combined treatments generally enhanced hydrocarbon biodegradation in comparison to both natural attenuation and the single inorganic fertilizer treatment. The inorganic fertilizer plus Ivey^? surfactant was the most efficient treatment in terms of Total Petroleum Hydrocarbon and light and heavy n-alkanes, showing an index of degradation of 1.4 and 1.3, respectively. Furthermore, biodegradation of heavy and branched n-alkanes was higher in microcosms treated with inorganic fertilizer plus ethanol (Index of degradation values of 1.6 and 1.5, respectively) indicating that combined treatments can be very effective in restoration of contaminated soil.     

Effective bioremoval of syntan using fungal laccase to reduce pollution from effluent

Syntans are synthetically prepared tanning agents from phenols that play an important role in leather making by enhancing the filling, grain characteristics and dyeing property. A considerable amount of syntan emanated in waste water contributes high pollution load with other heterocyclic aromatic compounds and causes serious environmental impact resulting in high oxygen demand. In order to overcome this, suitable biodegradation techniques have been developed using laccase from Penicillium chrysogenum. The influence of different environmental parameters on the biodegradation has also been studied which reveals that the maximum syntan degradation was obtained at pH 5.0, temperature at 32 °C for the duration of 48 h. Maximum biodegradation was found to be 96 and 94% for samples containing phenolic and melamine syntan. Ultraviolet spectra showed the peaks at around 280 nm for the presence of phenolic (DI) syntan and at 220 nm for melamine syntan which were disappeared later in the experimental sample indicating complete degradation of syntans. Fourier spectral analysis indicated that the peaks at the region between 1443–1574 and 1176 cm^?1 correspond to C=C stretching and C–H bending for aromatic region which were later disappeared in the experimental sample. Ultrapressure liquid chromatography elution profiles of syntans showed relatively shorter retention time indicating formation of oxidized products. Syntans, namely DI and FB6, showed reduction in chemical oxygen demand up to 87.71 ± 4 and 83.38 ± 5%, respectively, while total organic carbon reduction was achieved up to 82.37 and 80.72%, respectively. Toxicity studies revealed that seeds were well germinated using the treated (biodegradation) samples by crude laccase .     

Degradation of native wheat straw lignin by Streptomyces viridosporus T7A

Lignin is one of the major contributing factors toward the recalcitrance of lignocellulosic biomass. Understanding the process of lignin degradation in natural biological processes will provide useful information to develop novel biomass conversion technologies. Functional group changes in the lignin entities during the process may contribute to the cellulose degradation (utilization) by the microorganisms. In this study, compositional and advanced Fourier transform infrared, pyrolysis gas chromatography/mass spectrometry and ¹³C cross polarization/magic angle spinning nuclear magnetic resonance analysis were performed to explore the mechanism of biodegradation of wheat straw by Streptomyces viridosporus T7A. The results indicated that S. viridosporus T7A removed lignin and hemicelluloses as indicated by the increased carbohydrate/lignin ratio. Significant modification of carbonyl and methoxyl groups in the complex lignin structure was also evident. Most importantly, the quantitative results showed that lignin degradation was featured by deduction of guaiacyl unit. The results provide new insight for understanding lignin degradation by bacteria.     

Bioremediation of 2,4,6-trinitrotoluene-contaminated groundwater using unique bacterial strains: microcosm and mechanism studies

Groundwater at many military factory, munition storage and maneuver sites is contaminated by explosives chemicals that were released into the subsurface. The 2,4,6-trinitrotoluene (TNT) is among the most common explosive pollutants. In this study, two TNT-degrading strains, isolated from TNT-contaminated soils and wastewater sludge, were applied for TNT biodegradation. Based on the 16S rDNA sequence analyses, these two bacterial strains were identified as Achromobacter sp. and Klebsiella sp. via biochemical and DNA analyses. Microcosm study was conducted to evaluate the feasibility and efficiency of TNT biodegradation under aerobic conditions. Results indicate that TNT degradation by-products were detected in microcosms (inoculated with Achromobacter sp. and Klebsiella sp.) with cane molasses addition. Klebsiella sp. and Achromobacter sp. used TNT as the nitrogen source and caused completely removal of TNT. Two possible TNT biodegradation routes could be derived: (1) part of the TNT was transformed to nitrotoluene then transformed to nitrobenzene followed by the nitro substitute process, and trinitrobenzene, dinitrobenzene, and nitrobenzene were detected; and (2) TNT was transformed via the nitro substitute mechanism, and dinitrotoluene followed by nitrotoluene isomers were detected. The initial TNT degradation involved the reduction or removal of the nitro substitute to an amino derivative or free nitrite. Results show that the second route was the dominant TNT biodegradation pathway. The produced by-products were also degraded without significant accumulation during the degradation process. These findings would be helpful in designing a practical system inoculated with isolated TNT degradation strains for the treatment of TNT-contained groundwater.     

Assessment of MTBE biodegradation in contaminated groundwater using C and C analysis: Field and laboratory microcosm studies

Radiolabelled assays and compound-specific stable isotope analysis (CSIA) were used to assess methyl tert-butyl ether (MTBE) biodegradation in an unleaded fuel plume in a UK chalk aquifer, both in the field and in laboratory microcosm experiments. The ¹⁴C-MTBE radiorespirometry studies demonstrated widespread potential for aerobic and anaerobic MTBE biodegradation in the aquifer. However, δ¹³C compositions of MTBE in groundwater samples from the plume showed no significant ¹³C enrichment that would indicate MTBE biodegradation at the field scale. Carbon isotope enrichment during MTBE biodegradation was assessed in the microcosms when dissolved O₂ was not limiting, compared with low in situ concentrations (2 mg/L) in the aquifer, and in the absence of O₂. The microcosm experiments showed ubiquitous potential for aerobic MTBE biodegradation in the aquifer within hundreds of days. Aerobic MTBE biodegradation in the microcosms produced an enrichment of 7‰ in the MTBE δ¹³C composition and an isotope enrichment factor (ε) of −1.53‰ when dissolved O₂ was not limiting. However, for the low dissolved O₂ concentration of up to 2 mg/L that characterizes most of the MTBE plume fringe, aerobic MTBE biodegradation produced an enrichment of 0.5-0.7‰, corresponding to an ε value of −0.22‰ to −0.24‰. No anaerobic MTBE biodegradation occurred under these experimental conditions. These results suggest the existence of a complex MTBE-biodegrading community in the aquifer, which may consist of different aerobic species competing for MTBE and dissolved O₂. Under low O₂ conditions, the lower fractionating species have been shown to govern overall MTBE C-isotope fractionation during biodegradation, confirming the results of previous laboratory experiments mixing pure cultures. This implies that significant aerobic MTBE biodegradation could occur under the low dissolved O₂ concentration that typifies the reactive fringe zone of MTBE plumes, without producing detectable changes in the MTBE δ¹³C composition. This observed insensitivity of C isotope enrichment to MTBE biodegradation could lead to significant underestimation of aerobic MTBE biodegradation at field scale, with an unnecessarily pessimistic performance assessment for natural attenuation. Site-specific C isotope enrichment factors are, therefore, required to reliably quantify MTBE biodegradation, which may limit CSIA as a tool for the in situ assessment of MTBE biodegradation in groundwater using only C isotopes.     

Cadmium (II) distribution in complex aquatic systems containing ferrihydrite, bacteria and an organic ligand: The effect of bioactivity

The distribution of Cd²⁺ in the presence of phthalic acid (H₂L_p), ferrihydrite and bacteria (Comamonas spp.) was investigated in biologically active systems involving H₂L_p biodegradation. Tests showed that Cd²⁺ sorption onto bacteria, ferrihydrite and bacteria-ferrihydrite mixture increased with pH in all systems, irrespective of H₂L_p degradation or not. The use of bacterial growth medium, Bushnell Hass Broth modified for low phosphate, had negligible effect on Cd sorption. In the presence of ferrihydrite, no difference was observed between Cd²⁺ sorption in the ferrihydrite-live bacteria and in the ferrihydrite-dead bacteria systems as ferrihydrite proved to be the dominant sorption phase. Cadmium sorption to ferrihydrite and to bacterial cells was described using the diffuse layer model and a nonelectrostatic 4-site model, respectively, which were developed for systems lacking H₂L_p degradation. For systems experiencing H₂L_p degradation this modeling approach predicted the general trend of Cd²⁺ sorption-edge shift and gave good fits to the observed sorption data. The results obtained demonstrate that Cd²⁺ sorption in the biologically active system was reasonably estimated by a model developed for biologically inactive systems, although uncertainty exists due to processes involving H₂L_p biodegradation products and changes in the bacterial population.     

Une approche innovante pour modéliser la biodégradation des composés organochlorés volatils en aquifères poreux

The goal of this study was to develop an innovative chloroethene biodegradation module based on biological, thermodynamical and mechanistic concepts. The biodegradation scheme was based on the postulate that in each part of an aquifer only one degradation mechanism is dominant: the one involving the most energetic electron acceptor. Thus, the selection of the active degradation mechanism was a function of the concentration of different electron acceptors. Modified Monod-type kinetics was used in order to take into account the possible influence of some compounds on the biodegradation of a given organic compound. The numerical model developed was applied to a simple test case, whose results are presented here. To cite this article: F. Nex et al., C. R. Geoscience 338 (2006).     

Isolation,biodegradation ability and molecular detection of hydrocarbon degrading bacteria in petroleum samples from a Brazilian offshore basin

The detection of microorganisms with potential for biodeterioration and biodegradation in petroleum fields is of great relevance, since these organisms may be related to a decrease in petroleum quality in the reservoirs or damage in the production facilities. In this sense, petroleum formation water and oil samples were collected from the Campos Basin, Brazil, with the aim of isolating microorganisms and evaluating their ability to degrade distinct classes of hydrocarbon biomarkers (9,10-dihydrophenanthrene, phytane, nonadecanoic acid and 5α-cholestane). Twenty eight bacterial isolates were recovered and identified by sequencing their 16S rRNA genes. Biodegradation assays revealed that bacterial metabolism of hydrocarbons occurred through reactions based on oxidation, carbon–carbon bond cleavage and generation of new bonds or by the physical incorporation of hydrocarbons into microbial cell walls. Based on the biodegradation results, selective PCR-based systems were developed for direct detection in petroleum samples of bacterial groups of interest, namely Bacillus spp., Micrococcus spp., Achromobacter xylosoxidans, Dietzia spp. and Bacillus pumilus. Primer sets targeting 16S rRNA genes were designed and their specificity was confirmed in silico (i.e. computational analysis) and in PCR reactions using DNA from reference strains as positive and negative controls. Total DNA from oil was purified and the amplification tests revealed the presence of the target bacteria in the samples, unraveling a significant potential for petroleum deterioration in the reservoirs sampled, once proper conditions are present for hydrocarbon degradation. The application of molecular methods for rapid detection of specific microorganisms in environmental samples would be valuable as a supporting tool for the evaluation of oil quality in production reservoirs.     

Study on identification of leather industry wastewater constituents and its photocatalytic treatment

The present research work was intended to find out the useful information on identification, separation and photocatalytic degradation of organic compounds present in leather industry wastewater. The separation of organic compounds present in leather industry wastewater was carried out by solvent extraction. The separated crude extracted products were purified through column chromatography and characterized by UV–vis spectrophotometer, gas chromatography–mass spectrophotometer, liquid chromatography–mass spectrophotometer, ¹H and ¹³C Fourier-transform nuclear magnetic resonance spectroscopy. The elemental analysis of wastewater and solid residue was carried out by inductively coupled plasma-optical emission and X-ray fluorescence spectroscopy. The organic compounds such as nonadec-1-ene, 2-phenylethanol, 2,4-di-tert-butylphenol and other organic compounds in the leather industry wastewater were identified. Out of these organic compounds, 2-phenylethanol was photocatalytically degraded using standard Degussa P-25 TiO₂ (100 mg) photocatalyst under the irradiation of UV light. Result has been shown that 2-phenylethanol was transformed into 2-tert-butyl-4,6-dimethylphenol, 2,6-di-tert-butyl-4-methylphenol then the prolonged time (30 h) irradiation leads to 100 % degradation of 2-phenylethanol. Further possible degradation mechanism of 2-phenylethanol was proposed based on the electrospray ionization mass spectrometry analysis of degraded samples. The degradation of 2-phenylethanol was confirmed by chemical oxygen demand analysis of degraded samples. The physicochemical parameters such as pH, color, chemical oxygen demand, total dissolved solids, electrical conductivity and ionic chromatography analysis of the leather industry wastewater were also measured.     

Competitive interference during the biodegradation of cresols

Phenol and its methylated derivatives, cresol isomers, are hazardous pollutants that are commonly present in various industrial effluents and known to have detrimental effect on aquatic life as well as human health, due to their toxic and carcinogenic nature. It is essential, therefore, to reduce the concentration of these contaminants in industrial effluent to acceptable levels prior to being discharged into the environment. Bacterial cells of the strain Pseudomonas putida, with excellent biodegradation capabilities and high tolerance of cresols, were extracted and immobilized in polyvinyl alcohol (PVA) gel for cresols biodegradation. The biodegradation was carried out at different operating conditions, in both batch and continuous modes, using a cylindrical spouted bed bioreactor. Factors affecting o-cresol and m-cresol degradation were studied in batch experiments, and the results showed that the immobilized bacteria could tolerate cresols concentration up to 200 mg/l. Moreover, the experiments indicated that the biodegradation rate was highly affected by the operating parameters such as pH and temperature, with optimum ranges of 6–8 for pH and 30–35 °C for temperature. However, the optimum conditions were different for each cresol isomer. The potential of P. putida in degrading binary and ternary mixtures of cresols was also examined in the continuous process and compared with single component biodegradation. The experimental results revealed that the biodegradation of o-cresol was highly inhibited by the presence of p-cresol and m-cresol.     

Deciphering biodegradation effects on light hydrocarbons in crude oils using their stable carbon isotopic composition: A case study from the Gullfaks oil field, offshore Norway

Compound-specific isotope analysis has become an important tool in environmental studies and is an especially powerful way to evaluate biodegradation of hydrocarbons. Here, carbon isotope ratios of light hydrocarbons were used to characterise in-reservoir biodegradation in the Gullfaks oil field, offshore Norway. Increasing biodegradation, as characterised, for example, by increasing concentration ratios of Pr/n-C₁₇ and Ph/n-C₁₈, and decreasing concentrations of individual light hydrocarbons were correlated to ¹³C-enrichment of the light hydrocarbons. The δ¹³C values of C₄ to C₉n-alkanes increase by 7-3‰ within the six oil samples from the Brent Group of the Gullfaks oil field, slight changes (1-3‰) being observed for several branched alkanes and benzene, whereas no change (<1‰) in δ¹³C occurs for cyclohexane, methylcyclohexane, and toluene. Application of the Rayleigh equation demonstrated high to fair correlation of concentration and isotope data of i- and n-pentane, n-hexane, and n-heptane, documenting that biodegradation in reservoirs can be described by the Rayleigh model. Using the appropriate isotope fractionation factor of n-hexane, derived from laboratory experiments, quantification of the loss of this petroleum constituent due to biodegradation is possible. Toluene, which is known to be highly susceptible to biodegradation, is not degraded within the Gullfaks oil field, implying that the local microbial community exhibits rather pronounced substrate specificities. The evaluation of combined molecular and isotopic data expands our understanding of the anaerobic degradation processes within this oil field and provides insight into the degradative capabilities of the microorganisms. Additionally, isotope analysis of unbiodegraded to slightly biodegraded crude oils from several oil fields surrounding Gullfaks illustrates the heterogeneity in isotopic composition of the light hydrocarbons due to source effects. This indicates that both source and also maturity effects have to be well constrained when using compound-specific isotope analysis for the assessment of biodegradation.     

Biodegradation of cellulose acetate/poly(butylene succinate) membrane

Applying biodegradable polymers in membrane preparation for separation processes is expected to be helpful in solving waste disposal problem. In this study, biodegradable blend membranes of cellulose acetate (CA)/poly(butylene succinate) (PBS) were prepared and the microorganisms possessing the ability of degrading them were isolated from soil. The isolates were classified into two groups of bacteria and fungi. The membranes biodegradation after cultivation by the isolates in liquid media was further confirmed by weight loss measurement, Fourier transform infrared analysis and scanning electron microscopy. Findings revealed that CA degradation could be improved in the blend membrane structure. Moreover, strain BG106 and BG111 could degrade the membranes at the fastest rate among the other bacteria and fungi, respectively. To our knowledge, BG111 was found to belong to Alternaria sp. and this is the first report of its PBS degradation activity. Moreover, the PBS degradability of BG104 (B. Safensis), BG105 (Achromobacter insuavis) and BG106 (Brevibacterium halotolerans) strains was reported for the first time.     

Investigation of hydrocarbon biodegradation from a downhole profile in Bohai Bay Basin: Implications for the origin of 25-norhopanes

A suite of reservoir cores (oil sands) from a single well in Bohai Bay Basin, East China, displayed a progressive increase in petroleum biodegradation extent on the basis of bulk composition and 25-norhopane content. This fits with the proposal that subsurface petroleum biodegradation is dominantly an anaerobic process and usually occurs at the oil–water contact. It is likely that sequential microbial degradation of hydrocarbons under anoxic conditions does not occur in a true stepwise fashion, but is controlled by various factors such as concentration and solubility of hydrocarbons and their diffusion rate to the oil/water contact. In fact, 25-norhopanes were formed prior to the complete elimination of the acyclic, and mono- and bicyclic alkanes. An inverse response of the 22S/(22S + 22R) ratio between each extended 17α(H)-hopane and its corresponding 25-norhopane was observed as severe biodegradation occurred, supporting the proposal that the 25-norhopanes originate from demethylation of hopanes. Field observation revealed that biomarkers without extended alkyl side chains, such as oleanane, gammacerane and β-carotane, have significant resistance to biodegradation and can be used as naturally occurring “internal standards” to evaluate variations in other biomarkers. The results suggest that the quantity of 25-norhopanes showed a minor increase as the hopanes decreased significantly, i.e. only partial hopane conversion to the corresponding 25-norhopanes. Alternative degradation pathways for hopanes might occur in reservoirs, in addition to C-25 demethylation.     

Development of a two-stage washing and biodegradation system to remediate octachlorinated dibenzo-<Emphasis Type="Italic">p</Emphasis>-dioxin-contaminated soils

A two-stage system for octachlorinated dibenzo-p-dioxin (OCDD)-contaminated soil remediation was developed. Soil washing using emulsified oil (EO) was applied in the first stage for OCDD extraction followed by the second stage of bioremediation using P. mendocina NSYSU for remaining OCDD biodegradation. The major tasks included (1) determination of optimal soil washing conditions for OCDD extraction by EO, (2) evaluation of feasibility of OCDD biodegradation by P. mendocina NSYSU under aerobic cometabolic conditions using EO as the primary substrate, and (3) assessment of the effectiveness of OCDD removal using the two-stage system. During the soil washing stage, EO with two different oil-to-water ratios (1:50 and 1:200) and pore volumes were tested with initial soil OCDD concentration of 21,000 µg/kg. Results indicate that EO could effectively improve the solubility and desorption of OCDD in soils. Up to 74% of OCDD removal could be obtained after washing with 60 PVs of EO and dilution factor of 50. After the soil washing process, enriched P. mendocina NSYSU solution was added into the reactor to enhance the aerobic biodegradation of remaining OCDD in soils. P. mendocina NSYSU could use adsorbed EO globules as substrates and caused significant OCDD degradation via the aerobic cometabolic mechanism. Approximately 82% of the remaining OCDD could be removed after 50 days of operation, and P. mendocina NSYSU played important roles in OCDD biodegradation. Up to 87% of OCDD was removed through the EO washing and biodegradation process. The two-stage system is a potential technology to remediate dioxin-contaminated soils.     

Evaluation of the diagnostic ratios for the identification of spilled oils after biodegradation

Biodegradation, one of the most important weathering processes, alters the composition of spilled oil, making it difficult to identify the source of the release and to monitor its fate in the environment. A laboratory experiment was conducted to simulate oil spill weathering process of microbial degradation to investigate compositional changes in a range of source- and weathering-dependent molecular parameters in oil residues, and the conventional diagnostic ratios for oil spill identification were also evaluated. The conventional diagnostic ratios of n-alkane displayed obvious changes after biodegradation, especially for Pr/n-C₁₇ and Ph/n-C₁₈ with relative standard deviation more than 118.84 %, which suggests they are invalid for oil source identification of the middle-serious spill. Many polycyclic aromatic hydrocarbons (PAHs) are more resistant to biodegradation process than their saturated hydrocarbon counterparts, thus making PAHs to be one of the most valuable fingerprinting classes of hydrocarbons for oil identification. Biomarker ratios of hopanes and steranes were also useful for source identification even after moderate biodegradation, and the diagnostic ratios from them could be used in tracking origin and sources of hydrocarbon pollution. Finally, the carbon isotopic type curve may provide another diagnostic means for correlation and differentiation of spilled oils, and be particularly valuable for lighter refined products or severely biodegraded oils, the source of which may be difficult to identify by routine biomarker techniques.     

Synergistic degradation of diazo dye Direct Red 5B by Portulaca grandiflora and Pseudomonas putida

Plants and bacterial consortium of Portulaca grandiflora and Pseudomonas putida showed complete decolorization of a sulfonated diazo dye Direct Red 5B within 72 h, while in vitro cultures of P. grandiflora and P. putida independently showed 92 and 81 % decolorization within 96 h, respectively. A significant induction in the activities of lignin peroxidase, tyrosinase, 2,6-dichlorophenol indophenol reductase and riboflavin reductase was observed in the roots of P. grandiflora during dye decolorization; whereas, the activities of laccase, veratryl alcohol oxidase and 2,6-dichlorophenol indophenol reductase were induced in the cells of P. putida. Plant and bacterial enzymes in the consortium gave an enhanced decolorization of Direct Red 5B synergistically. The metabolites formed after dye degradation analyzed by UV–Vis spectroscopy, Fourier transformed infrared spectroscopy and high performance liquid chromatography confirmed the biotransformation of Direct Red 5B. Differential fate of metabolism of Direct Red 5B by P. grandiflora, P. putida and their consortium were proposed with the help of gas chromatography–mass spectroscopy analysis. P. grandiflora metabolized the dye to give 1-(4-diazenylphenyl)-2-phenyldiazene, 7-(benzylamino) naphthalene-2-sulfonic acid, 7-aminonaphthalene-2-sulfonic acid and methylbenzene. P. putida gave 4-hydroxybenzenesulfonic acid and 4-hydroxynaphthalene-2-sulfonic acid and benzamide. Consortium showed the formation of benzenesulfonic acid, 4-diazenylphenol, 6-aminonaphthalen-1-ol, methylbenzene and naphthalen-1-ol. Consortium achieved an enhanced and efficient degradation of Direct Red 5B. Phytotoxicity study revealed the nontoxic nature of metabolites formed after parent dye degradation. Use of such combinatorial systems of plant and bacteria could prove to be an effective and efficient strategy for the removal of textile dyes from soil and waterways.     

The effect of biodegradation on polycyclic aromatic hydrocarbons in reservoired oils from the Liaohe basin, NE China

The occurrence and distribution of polycyclic aromatic hydrocarbons (PAHs) has been studied in oil columns from the Liaohe basin, NE China, characterized by varied degrees of biodegradation. The Es3 oil column has undergone light to moderate biodegradation – ranging from levels 2 to 5 on the [Peters, K.E., Moldowan, J.M., 1993. The Biomarker Guide: Interpreting Molecular Fossils in Petroleum and Ancient Sediments. Prentice Hall, Englewood Cliffs, NJ, p. 363] scale (abbreviated as ‘PM level’) – while the shallower Es1 column has undergone more severe biodegradation, ranging from PM level 5 to 8. Both columns show excellent vertical biodegradation gradients, with degree of biodegradation increasing with increasing depth toward the oil–water contact (OWC). The compositional gradients in the oil columns imply mass transport control on degradation rates, with degradation occurring primarily at the OWC. The diffusion of hydrocarbons to the OWC zone will be the ultimate control on the maximum degradation rate. The chemical composition and physical properties of the reservoired oils, and the ‘degradation sequence’ of chemical components are determined by mixing of fresh oil with biodegraded oil.The PAH concentrations and molecular distributions in the reservoired oils from these biodegraded columns show systematic changes with increasing degree of biodegradation. The C₃₊-alkylbenzenes are the first compounds to be depleted in the aromatic fraction. Concentrations of the C_0–5-alkylnaphthalenes and the C_0–3-alkylphenanthrenes decrease markedly during PM levels 3–5, while significant isomer variations occur at more advanced stages of biodegradation (>PM level 4).The degree of alkylation is a critical factor controlling the rate of biodegradation; in most cases the rate decreases with increasing number of alkyl substituents. However, we have observed that C₃-naphthalenes concentrations decrease faster than those of C₂-naphthalenes, and methylphenanthrenes concentrations decrease faster than that of phenanthrene. Demethylation of a substituted compound is inferred as a possible reaction in the biodegradation process.Differential degradation of specific alkylated isomers was observed in our sample set. The relative susceptibility of the individual dimethylnaphthalene, trimethylnaphthalene, tetramethylnaphthalene, pentamethylnaphthalene, methylphenanthrene, dimethylphenanthrene and trimethylphenanthrene isomers to biodegradation was determined. The C₂₀ and C₂₁ short side-chained triaromatic steroid hydrocarbons are degraded more readily than their C_26–28 long side-chained counterparts. The C_21–22-monoaromatic steroid hydrocarbons (MAS) appear to be more resistant to biodegradation than the C_27–29-MAS.Interestingly, the most thermally stable PAH isomers are more susceptible to biodegradation than less thermally stable isomers, suggesting that selectivity during biodegradation is not solely controlled by thermodynamic stability and that susceptibility to biodegradation may be related to stereochemical structure. Many commonly used aromatic hydrocarbon maturity parameters are no longer valid after biodegradation to PM level 4 although some ratios change later than others. The distribution of PAHs coupled with knowledge of their biodegradation characteristics constitutes a useful probe for the study of biodegradation processes and can provide insight into the mechanisms of biodegradation of reservoired oil.     

Biodegradation of cyanide and evaluation of kinetic models by immobilized cells of <Emphasis Type="Italic">Serratia marcescens</Emphasis> strain AQ07

Immobilized form of Serratia marcescens strain AQ07 was experimented for cyanide biodegradation. Cyanide degradation (200 ppm) was achieved after 24-h incubation. Three parameters were optimized which included gellan gum concentration, beads size, and number of beads. In accordance with one-factor-at-a-time method, cyanide removal was optimum at 0.6% w/v gellan gum gel, 0.3-cm-diameter beads, and 50 beads number. It was able to withstand cyanide toxicity of 800 ppm, which makes it very suitable candidate in cyanide remediation. Beads reusability indicates one-cycle ability. The first cycle removed 96.3%, while the second removed 78.5%. Effects of heavy metals at 1.0 ppm demonstrated that mercury has a considerable effect on bacteria, inhibiting degradation to 61.6%, while other heavy metals have less effect, removing 97–98%. Maximum specific degradation rate of 0.9997 h^?1 was observed at 200 ppm cyanide concentration. Gellan gum was used as the encapsulation matrix. ?-picoline-barbituric acid spectrophotometric analytical method was used to optimize the condition in buffer medium integrated with potassium cyanide via one-factor-at-a-time and response surface method. The range of cyanide concentrations used in this research, specific biodegradation rate was obtained to model the substrate inhibition kinetics. This rate fits to the kinetic models of Teisser, Aiba and Yano, which are utilized to elucidate substrate inhibition on degradation. One-factor-at-a-time approach parameters were adopted because it removes more cyanide compared to response surface methodology modules. The predicted biokinetic constant from this model suggests suitability of the bacteria for use in cyanide treatment of industrial waste effluents.