Microorganisms For Biodegradation Research Articles

Highly selective adsorption and biodegradation of emulsified oil by microorganisms embedded in SiO2 hollow sphere bioreactor

Highly efficient elimination and disposal of oils and organic contaminants from water is of great importance for the sustainable development of modern society. In this work, micron-sized “single pore” silica hollow spheres (SHMs) bioreactors were prepared using (W/O/W) ternary-phase microemulsion, and the size of pores was adjusted to the concept of “single-pore” composite microorganism bioreactor, preparation of single-pore silica hollow spheres with an average pore size of 8.572 μm, which enables the SHMs bioreactors to load microorganisms for oils biodegradation. The outer layer was sprayed with a layer of silica nanoparticles with a diameter of 500 nm produced by silane hydrolysis, which encapsulated the inner “single-pore” SHMs to form a core–shell structure (M/Microbe@SHMs). This micro-nano core–shell structure exhibits superhydrophobicity and superlipophilicity, which gives it excellent selective adsorption capacity. Interestingly, M/Microbe@SHMs have excellent emulsion-breaking effects in oil–water separation. In addition to the simultaneous oil/water separation ability, the adsorbed oil and grease can be subsequently degraded to CO2 and H2O by microorganisms' action in the inner layer of M/Microbe@SHMs. Based on this excellent selective adsorption and oil/water separation capacity, while one-step in-situ biodegradation, our microbial bioreactor may have a potential for a wide range of practical applications in wastewater treatment.

Bio-prospective of Acidophile Microorganisms in Biodegradation of NSAIDs

Bio-prospective of Acidophile Microorganisms in Biodegradation of NSAIDs

Biodegradation of soil agrochemical contamination mitigates the direct horizontal transfer risk of antibiotic resistance genes to crops

Microorganisms can drive a substrate-specific biodegradation process to mitigate soil contamination resulting from extensive agrochemical usage. However, microorganisms with high metabolic efficiency are capable of adapting to the co-occurrence of non-substrate contaminants in the soil (particularly antibiotics). Therefore, the utilization of active microorganisms for biodegradation raises concerns regarding the potential risk of antibiotic resistance development. Here, the horizontal transfer risk of antibiotic-resistance genes (ARGs) in the soil-plant biota was assessed during biodegradation by the newly isolated Proteus terrae ZQ02 (which shortened the half-life of fungicide chlorothalonil from 9.24 d to 2.35 d when exposed to tetracycline). Based on metagenomic analyses, the distribution of ARGs and mobile genetic elements (MGEs) was profiled. The ARGs shared with ∼118 core genes and mostly accumulated in the rhizosphere and maize roots. After ZQ02 was inoculated, the core genes of ARGs reduced significantly in roots. In addition, the Pseudomonas and Proteus genera were identified as the dominant microbial hosts of ARGs and MGEs after ZQ02 adoption. The richness of major ARG hosts increased in soil but barely changed in the roots, which contributed to the mitigation of hosts-mediated ARGs transfer from soil to maize. Finally, the risk of ARGs has been assessed. Compared with the regular planting system, the number of risky ARGs declined from 220 (occupied 4.77 % of the total ARGs) to 143 (occupied 2.67 %) after biodegradation. Among these, 23 out of 25 high-risk genes were aggregated in the soil whereas only 2 genes were identified in roots, which further verified the low antibiotic resistance risk for crop after biodegradation. In a nutshell, this work highlights the critical advantage of ZQ02-based biodegradation that alleviating the ARGs transfer risks from soil to crop, which offers deeper insights into the versatility and feasibility of bioremediation techniques in sustainable agriculture.

Molecular and biochemical characterization of solid waste biodegrading microbes isolated from municipal waste dump site

Solid waste dump site-based pollution is one of the colossal health concerns globally due to presence of cellulose, starch, protein, and lipids, which is a perfect nutrient waste for the development of biodegrading potential microbes. The current study aimed to determine the productive microorganisms for waste biodegradation. Ten samples were collected from different areas of Karachi waste dump sites. The identification and characterization of isolates were done by morphological and biochemical tests. The isolated microbes were qualitatively screened for the action of making industrially key bio-enzymes. The potential enzymes producing microbes were subjected to waste degradation test for 90 days. Changes of odor, color and weight loss of decomposing garbage were noted. The highest degradation ability in term of weight loss was shown by Aspergillus (SSI14) and Bacillus (SSI6). Four metals (zinc sulphate, cadmium chloride, copper sulphate and iron sulphate) were chosen for the purpose of metals tolerance test and minimum inhibitory concentration (MIC) of the isolated microbial strains. Current study reported that Zn was found to be more lethal in in comparison to Cu and Fe. Molecular identification of the isolated microbes was done by polymerase chain reaction. The microbial strains were characterized by the polymerase chain reaction (PCR) followed by confirmation of product by agarose gel electrophoresis. The findings can be served as baseline data to develop microbial apparatus for biodegradation and management of solid waste.

Effects of filling methods on the degradation of ethyl acetate and the microbial community in biofilters

Two biofilters (BFs) for treating ethyl acetate (EA) were constructed with magnetite, activated carbon, perlite and gravel added via layered filling (BF1) or mixed filling (BF2). This study demonstrated the effect of filling method on the degradation of EA and the microbial community in the BFs. The results indicated that the EA removal efficiency (RE) of BF1 and BF2 reached 86.3 ± 3.0 % and 88.9 ± 2.1 %, respectively, under low inlet load (L-IL; (224 g/(m3·h)). Meanwhile, BF2 exhibited stabler RE than BF1 at high IL. BF1 achieved the highest REs of total phosphorus (TP), total nitrogen (TN) and ammonia nitrogen (NH4+-N) under moderate inlet load (M-IL; 336 g/(m3·h)), with average values of 95.8 ± 3.5 %, 83.4 ± 0.4 %, and 85.7 ± 0.3 %, respectively. The removal of TP, TN and NH4+-N in BF2 was superior than BF1 at L-IL and M-IL condition. Moreover, the genera Burkholderia, Acinetobacter, unclassified_Rhizobiales and unclassified_Burkholderiales were the dominant EA-degrading bacteria in BF1, while the EA-degrading bacteria in BF2 were dominated by unclassified_Chloroflexi, unclassified_Bacteroidetes and unclassified_Anaerolineaceae. Furthermore, the mechanism investigation of the mechanism revealed that the types of filling method affect EA degradation by shifting the abundance and diversity of key microorganisms in biodegradation. This study provides an effective strategy for improving the biodegradation efficiency of volatile organic compounds VOCs.

Biostrategies for the removal of microplastics: A Review

Recent studies on plastic pollution have shown that microscopic plastic particles or microplastics are ubiquitous. Both abiotic and biotic components are affected by microplastics. There are several ways to get rid of microplastics, that include recycling, landfilling, incineration, and biodegradation. Biodegradation is still a widely used remediation technology due to its significant economic and environmental benefits. One or more bio-cultures, such as bacteria, mould, yeast, and algae, can be used for biodegradation. In this review, we look through the contributions of microorganisms in biodegradation and other biotechnological techniques to speed up the process.

Treatment of thiocyanate-containing wastewater: a critical review of thiocyanate destruction in industrial effluents.

Thiocyanate is a common pollutant in gold mine, textile, printing, dyeing, coking and other industries. Therefore, thiocyanate in industrial wastewater is an urgent problem to be solved. This paper reviews the chemical properties, applications, sources and toxicity of thiocyanate, as well as the various treatment methods for thiocyanate in wastewater and their advantages and disadvantages. It is emphasized that biological systems, ranging from laboratory to full-scale, are able to successfully remove thiocyanate from factories. Thiocyanate-degrading microorganisms degrade thiocyanate in autotrophic manner for energy, while other biodegrading microorganisms use thiocyanate as a carbon or nitrogen source, and the biochemical pathways and enzymes involved in thiocyanate metabolism by different bacteria are discussed in detail. In the future, degradation mechanisms should be investigated at the molecular level, with further research aiming to improve the biochemical understanding of thiocyanate metabolism and scaling up thiocyanate degradation technologies from the laboratory to a full-scale.

Selective adsorption and efficient degradation of oil pollution by microorganisms immobilized natural biomass aerogels with aligned channels

Efficient elimination of organic pollution from wastewater is of great importance for sustainable human development. In this paper, natural biomass of lotus root (LR) and sorghum straw (SS), which showed aligned structure after treatment, was used to prepare efficient, low-cost, selective adsorption and self-floating microbial immobilization materials by hydrophobic modification assembly for the efficient degradation of diesel. By immobilizing microorganisms in aligned structured lotus flower (ALR) and sorghum straw (ASS) aerogels, hydrophobically modifying the aerogel surfaces with SiO2/PDMS, and assembling them with polyurethane foam to form hydrophobically immobilized microbial bilayer structured self-floating composites (SA6-ALR4@SiO2/PDMS and SA6-ASS4@SiO2/PDMS), diesel in water can be selectively adsorbed for biodegradation. The kinetic and thermodynamic parameters of diesel degradation process were investigated by treating oily wastewater and the effect of different carriers on microbial tolerance under different factors (temperature, pH, degradation substrate concentration, salinity) was examined. The results showed that the different carriers were effective in the degradation of diesel. However, the rich vertical aligned channels and excellent self-floating characteristics of SA6-ALR4@SiO2/PDMS accelerated the mass transfer rate between microorganisms and pollutants, achieving a high degradation rate of 96.25% for diesel in 276 h, which was better than that of 33.06% for free microorganisms under the same conditions. The degradation of oily wastewater by immobilized microorganisms follows first order kinetics. Moreover, this degradation process is spontaneous and the ΔG value is less than 0 at different temperatures. Compared with the existing methods using natural biomass to treat oily wastewater or applying only free microorganisms for biodegradation to remove oily wastewater, these methods have the disadvantages of poor selective adsorption, easy settling and low efficiency. It has greater advantages and application potential in on-site oil spill accident treatment, and opens up an effective green channel for the purification of oily wastewater.

Biodegradation of Alprazolam in Pharmaceutical Wastewater Using Mesoporous Nanoparticles-Adhered Pseudomonas stutzeri

The release of pharmaceutical wastewaters in the environment is of great concern due to the presence of persistent organic pollutants with toxic effects on environment and human health. Treatment of these wastewaters with microorganisms has gained increasing attention, as they can efficiently biodegrade and remove contaminants from the aqueous environments. In this respect, bacterial immobilization with inorganic nanoparticles provides a number of advantages, in terms of ease of processing, increased concentration of the pollutant in proximity of the cell surface, and long-term reusability. In the present study, MCM-41 mesoporous silica nanoparticles (MSN) were immobilized on a selected bacterial strain to remove alprazolam, a persistent pharmaceutical compound, from contaminated water. First, biodegrading microorganisms were collected from pharmaceutical wastewater, and Pseudomonas stutzeri was isolated as a bacterial strain showing high ability to tolerate and consume alprazolam as the only source for carbon and energy. Then, the ability of MSN-adhered Pseudomonas stutzeri bacteria was assessed to biodegrade alprazolam using quantitative HPLC analysis. The results indicated that after 20 days in optimum conditions, MSN-adhered bacterial cells achieved 96% biodegradation efficiency in comparison to the 87% biodegradation ability of Pseudomonas stutzeri freely suspended cells. Kinetic study showed that the degradation process obeys a first order reaction. In addition, the kinetic constants for the MSN-adhered bacteria were higher than those of the bacteria alone.

Microbial Degradation of 2-Methylisoborneol in Forest Soil.

Microorganisms use a complex array of chemical compounds to interact with their surroundings. They produce and process different molecules in response to changes in the environment or in their metabolism. One of the most well-known volatile organic compounds produced by microorganisms is the C11-terpenoid 2-methylisoborneol (2-MIB), which has received attention because of the off-flavor it confers to fresh and reservoir water as well as to cultured fish. Cleaning water supplies of the off-flavor 2-MIB has been of interest for the scientific community for years, with the use of techniques that are either expensive, e. g., activated carbon, or create toxic byproducts, e. g., ozonation. In the present study, soil samples from nature were collected from a forest and the volatile organic compounds produced by microbes were extracted and analyzed with focus on non-canonical terpenoid structures. HS-SPME-GC/MS analysis of soil samples revealed 1-methylcamphene (1-MC), 2-methylenebornane (2-MB) and 2-MIB as C11-terpenoids. Due to the high 1-MC/2-MIB ratio compared to previous reports, it was hypothesized that microbial degradation of 2-MIB was in place. Addition of synthetic 2-MIB to biologically active soil revealed complete degradation of the pollutant to 2-MB, 1-MC and 2-methyl-2-bornene (2-M2B). The results suggest the potential of using respective natural microorganisms for biodegradation of 2-MIB, with applications in water treatment, fishery and soil ecology.

Selective Adsorption and Efficient Degradation of Petroleum Hydrocarbons by a Hydrophobic/Lipophilic Biomass Porous Foam Loaded with Microbials.

Highly efficient elimination of petroleum pollution is of great importance for addressing environmental issues and social sustainability. In this study, we demonstrate a novel strategy for efficient elimination of petroleum pollution by selective adsorption of it by an ultralight hydrophobic/lipophilic microorganism-loaded biomass porous foam (BTS-MSFT4@MTMS) followed by a green degradation of adsorbates under mild conditions. The porous structure of biomass porous foam (MSFT) could provide plenty of room for immobilization of Bacillus thuringiensis (BTS), while a simple surface modification of the MSFT load with a BTS strain (BTS-MSFT4) by methyltrimethoxysilane (MTMS) could change its wettability from hydrophilic to lipophilic, which makes selective adsorption of hydophobic petroleum pollution from water for biodegradation possible. As expected, using a petroleum n-hexadecane solution with a concentration of 3% as a model oily wastewater, the as-prepared BTS-MSFT4@MTMS possesses both a superior selective adsorption of ca. 99% and high degradation activity with a high degradation rate of up to 86.65% within 8 days under the conditions of 37 °C, 120 r min-1, and pH = 7, while the degradation rates for the BTS-MSFT4 and the free BTS strain were measured to be only 81.62 and 65.65%, respectively, under the same conditions. In addition, the results obtained from the study on environment tolerance show that the BTS-MSFT4@MTMS exhibits a strong tolerance under different conditions with various pHs, temperatures, and initial concentrations. Compared with the existing methods for removal of petroleum pollution by direct adsorption of petroleum pollution via superoleophilic porous materials or applying free microorganisms for biodegradation only, which suffers the drawbacks of low selectivity or poor efficiency, our method has great advantages of cost-effectiveness, scalable fabrication, and high efficiency without secondary pollution. Moreover, such a two-in-one strategy by integration of both selective adsorption and biodegradation into biodegradable BTS-MSFT4@MTMS may particularly have great potential for practical application in environmental remediation.

Enhanced biodegradation and valorization of drilling wastewater via simultaneous production of biosurfactants and polyhydroxyalkanoates by Pseudomonas citronellolis SJTE-3

Pseudomonas citronellolis SJTE-3 was isolated as a highly efficient microorganism for biodegradation and valorization of drilling fluids (DF) wastewater. The strain metabolised DF and oily mud exhibiting up to 93%, 86%, 85% and 88% of chemical oxygen demand (COD), n-dodecane, n-tetradecane and naphthalene removal efficiency respectively. Enhanced bioconversion was enabled through production of biosurfactants that reduced the surface tension of water by 53% and resulted in 43.3% emulsification index (E24), while synthesizing 24% of dry cell weight (DCW) as medium-chain-length polyhydroxyalkanoates (PHA). Expression from the main pathways for alkanes and naphthalene biodegradation as well as biosurfactants and PHA biosynthesis revealed that although the alkanes and naphthalene biodegradation routes were actively expressed even at stationary phase, PHA production was stimulated at late stationary phase and putisolvin could comprise the biosurfactant synthesized. The bioconversion of toxic petrochemical residues to added-value thermoelastomers and biosurfactants indicate the high industrial significance of P. citronellolis SJTE-3.

The role of microorganisms in biodegradation of chitosan/tannic acid materials

High utilization of thermoplastic polymers with low degradation rates as packaging materials generates a large amount of waste. Therefore, it should be replaced by natural polymers that can be degraded by microorganisms. In this paper, chitosan (CTS)/tannic acid (TA) materials in the weight ratios of 80CTS/20TA and 50CTS/50TA were prepared as potential packaging materials. The results showed that these materials were similarly degraded in soil and compost. However, in comparison to 50CTS/50TA, 80CTS/20TA was slightly better degraded in soil. After 14 days of biodegradation, the chemical structure of materials was changed resulting from adhesion of the microorganisms. The smallest changes were observed on 80CTS/20TA film. Bacterial species were collected and identified from materials after the degradation process. Microorganisms with the highest hydrolytic activity were chosen for the degradation study. Biodegradation and hydrolytic activity were observed only in a few strains, which indicate difficulties in material degradation. Soil bacteria degraded the films better than bacteria isolated from the compost. This study showed also that consortia of bacteria added to soil and compost had a positive effect on the biodegradation of the tested materials and increased the biodegradation of these materials in the studied environments.

A Novel Bioremediation Technique for Petroleum Hydrocarbons by Bacterial Consortium Immobilized on Goethite-chitosan Nanocomposite

ABSTRACT Environmental pollution by petroleum hydrocarbon is one of the significant concerns of the contemporary world. This paper deals with the relevant environmental issues concerning the oil pollution of the petroleum industry. There is a need for further development of sustainable remediation technologies. Nineteen petroleum-degrading bacteria were isolated from an oil-polluted soil in the Suez oil processing company in Egypt. However, two bacterial species showed the highest growth rate of oil hydrocarbons. These isolates were identified by 16S rDNA gene sequence analysis into Flavobacterium johnsoniae BS1 (NCBI Gene Bank Accession no. MT740243) and Shewanella baltica BS2 (NCBI Gene Bank Accession no. MT740157). Ionic liquids prepared the goethite-chitosan nanocomposite assisted synthetic hydrothermal method. The antibacterial activity of synthesized nanocomposite on BS1and BS2 was determined. The two oil-degrading bacterial strains were immobilized onto the surface of the prepared nanocomposite. Pure and bacterial consortium studied the bioremediation process without/with nanocomposite. The remaining oil after bioremediation was extracted. Study results demonstrated that the affinity between the surface of bacterial cells and the prepared nanocomposite was investigated using scanning electron microscopy (SEM). From the antibacterial activity test of nanocomposite, there is no toxic effect on the two biodegrading microorganisms. The remaining oil after biodegradation showed that immobilized bacterial consortium achieved the maximum degradation efficiency 93.32% after 3 days of incubation. Biodegradation of different polyaromatic hydrocarbons was also studied, and immobilized bacterial consortium showed good biodegradation capabilities compared to those of free and pure cells. The nanocomposite catalyst increases the microbiological reaction rates by stimulating the activity of microbes during the biodegradation process. With this excellent biodegradation efficiency, these results suggested that the immobilized BS1 and BS2 consortium entailed high potential treatment for industrial applications for the biodegradation of oil-contaminated soil.

Isolation and identification of a 2,3,7,8-Tetrachlorodibenzo-P-dioxin degrading strain and its biochemical degradation pathway

This study aims to find a high-efficiency degradation strain which can biodegrade the 2,3,7,8-Tetrachlorodibenzo-P-dioxin (2,3,7,8-TCDD). In this paper, a new fungus strain was isolated from activated sludge of Dagu Drainage River in Tianjin which was able to degrade 2,3,7,8-TCDD in the medium. Based on its morphology and phylogenetic analysis of its 18S rDNA sequence, the strain was identified as Penicillium sp. QI-1. Response surface methodology using central composite rotatable design of cultural conditions was successfully employed for optimization resulting in 87.9 % degradation of 2,3,7,8-TCDD (1 µg/mL) within 6 days. The optimum condition for degrading 2,3,7,8-TCDD was at 31℃ and pH 7.4. The biodegradation process was fitted to a first-order kinetic model. The kinetic equation was Ct=0.939e− 0.133t and its half-life was 5.21d. The fungus strain degraded 2,3,7,8-TCDD to form intermediates, they were 4,5-Dichloro-1,2-benzoquinone, 4,5-Dichlorocatechol, 2-Hydrooxy-1,4-benzoquinone, 1,2,4-Trihydroxybenzene and β-ketoadipic acid. A novel degradation pathway for 2,3,7,8-TCDD was proposed based on analysis of these metabolites. The results suggest that Penicillium sp. QI-1 may be an ideal microorganism for biodegradation of the 2,3,7,8-TCDD-contaminated environments.

English

Food additives Azo dyes are synthetic compounds added to foods to impart color and improve their properties. Some azo dyes have been banned as food additives due to toxic, mutagenic, and carcinogenic side ei¬€ects. Long exposure to foods containing azo dye leads to chronic toxicity. Some microorganisms are capable to degrade these dyes and convert them to aromatic amines. In human body, microbiota can play a vital role in biodegradation of azo dyes by producing azo reductase. Aromatic amines are toxic, water-soluble and well absorbed via human intestine. In the current study, the role of microorganisms in biodegradation of six dyes related to azo group was discussed. These dyes are: Tartrazine E102, Sunset Yellow E110, Ponceau E124, Azorubine E122, Amaranth E123, and Allura Red E129 which are classified as the most harmful food additive dyes. Key word: Food additive, azo dyes, microorganisms, azo reductase, aromatic amines.

The potential of cold-adapted microorganisms for biodegradation of bioplastics

Due to the extensive use of plastics, their quantity in the environment is constantly increasing, which creates a global problem. In the present study, we sought to isolate, test and identify Antarctic microorganisms which possess the ability to biodegrade bioplastics such as poly(ε-caprolactone) (PCL), poly(butylene succinate) (PBS) and poly(butylene succinate-co-butylene adipate) (PBSA) at low temperatures. 161 bacterial and 38 fungal isolates were isolated from 22 Antarctic soil samples. Among them, 92.16% of bacterial and 77.27% of fungal isolates formed a clear zone on emulsified PBSA, 98.04% and 81.82% on PBS and 100% and 77.27% on PCL as an additive to minimal medium at 20 °C.Based on the 16S and 18S rRNA sequences, bacterial strains were identified as species belonging to Pseudomonas and Bacillus and fungal strains as species belonging to Geomyces, Sclerotinia, Fusarium and Mortierella, while the yeast strain was identified as Hansenula anomala. In the biodegradation process conducted under laboratory conditions at 14, 20 and 28 °C, Sclerotinia sp. B11IV and Fusarium sp. B3′M strains showed the highest biodegradation activity at 20 °C (49.68% for PBSA and 33.7% for PCL, 45.99% for PBSA and 49.65% for PCL, respectively). The highest biodegradation rate for Geomyces sp. B10I was noted at 14 °C (25.67% for PBSA and 5.71% for PCL), which suggested a preference for lower temperatures (at 20 °C the biodegradation rate was only 11.34% for PBSA, and 4.46% for PCL). These data showed that microorganisms isolated from Antarctic regions are good candidates for effective plastic degradation at low temperatures.

Biodegradation of low viscosity spindle oil causing environmental pollution.

Three hydrocarbon degrading microorganisms were isolated from the soil samples collected from the storage sites of low viscosity spindle oil containers and identified on the basis of morphological and biochemical characteristics as Aeromonas hydrophila, Bacillus subtilis and Staphylococcus aureus. The study has revealed high ability of these microorganisms for oil biodegradation. The results have indicated that all isolates had the potential to breakdown the hydrocarbon. The most efficient bacteria among these examined was Aeromonas hydrophila which biodegraded almost all tested hydrocarbon giving a treatment percentage of 98% within 30days which was considered as the perfect period for degradation. Also, a small scale was designed to treat the spindle oil with the using of oxidation process and all the tested organic materials were biodegraded in a treatment percentage of 100% within retention time of 20days.

Kinetic Study of the Biodegradation of Acephate by Indigenous Soil Bacterial Isolates in the Presence of Humic Acid and Metal Ions.

Many bacteria have the potential to use specific pesticides as a source of carbon, phosphorous, nitrogen and sulphur. Acephate degradation by microbes is considered to be a safe and effective method. The overall aim of the present study was to identify acephate biodegrading microorganisms and to investigate the degradation rates of acephate under the stress of humic acid and most common metal ions Fe(III) and copper Cu(II). Pseudomonas azotoformanss strain ACP1, Pseudomonas aeruginosa strain ACP2, and Pseudomonas putida ACP3 were isolated from acephate contaminated soils. Acephate of concentration 100 ppm was incubated with separate strain inoculums and periodic samples were drawn for UV—visible, FTIR (Fourier-transform infrared spectroscopy) and MS (Mass Spectrometry) analysis. Methamidophos, S-methyl O-hydrogen phosphorothioamidate, phosphenothioic S-acid, and phosphenamide were the major metabolites formed during the degradation of acephate. The rate of degradation was applied using pseudo-first-order kinetics to calculate the half-life (t1/2) values, which were 14.33–16.72 d−1 (strain(s) + acephate), 18.81–21.50 d−1 (strain(s) + acephate + Cu(II)), 20.06 –23.15 d−1 (strain(s) + acephate + Fe(II)), and 15.05–17.70 d−1 (strains + acephate + HA). The biodegradation efficiency of the three bacterial strains can be ordered as P. aeruginosa > P. putida > P. azotoformans. The present study illustrated the decomposition mechanism of acephate under different conditions, and the same may be applied to the removal of other xenobiotic compounds.

Effect of Various Isolated Microbial Consortiums on the Biodegradation Process of Precipitated Asphaltenes from Crude Oil

One of the serious problems in the oil industry is precipitation and deposition of asphaltenes in the different oil production stages including formation, wellbore, production tubing, flow lines, and separation units. This phenomenon causes a dramatic increase in the cost of oil production, processing, and transferring. Thus, it seems to be very necessary to use the removing methods for precipitated asphaltenes in different crude oil production and transferring stages. In this study, the ability of microorganisms for biodegradation of precipitated asphaltenes was investigated. For this purpose, four bacterial consortiums were isolated from oil-contaminated soil, crude oil, reservoir water, and oil sludge samples of an oil field located in the southwest of Iran. Based on the results of the designed experiments, by using response surface methodology (RSM) and central composite design, the bacterial consortiums were cultured in the flasks. Three levels of temperatures, salinity, pH, and initial asphaltene concentration as the substrate were considered as the parameters of culture medium and incubated growth mediums for 60 days. The maximum asphaltene biodegradation was 46.41% caused by the crude oil consortium including Staphylococcus saprophyticus sp. and Bacillus cereus sp. at 45 °C, salinity 160 g·L–1, pH 6.5, and 25 g·L–1 initial asphaltene concentration. Also, it was observed that the negative or positive impacts of culture media conditions such as temperature and salinity on asphaltene degradation depended on the type of the available bacterial consortium. The carbon–hydrogen–nitrogen–sulfur analysis showed that carbon, hydrogen, nitrogen, and in some cases, the sulfur in biodegraded samples are less than in control samples. Moreover, Fourier transform infrared analysis indicated that the alkyne groups were less resistant to biodegradation and were eliminated thoroughly after 2 months of incubation. In addition, alkane components were partially removed in treated asphaltene fraction. The parameters of culture medium were optimized by RSM, and besides, their effects on the performance of bacteria in the asphaltene biodegradation process were discussed. The validity of some available kinetic models to describe the behavior of the studied bacteria consortium was investigated, and it was observed that Tessier, Moser, and Contois models accurately predict the values of asphaltenes and biomass concentration at 30, 45, and 60 °C, respectively.