Showing 6 results for Biodegradation
Volume 5, Issue 1 (1-2019)
Abstract
Background: Biodegradation is the metabolic ability of some microorganisms in degrading or transforming the organic and inorganic contaminants into less harmful and non-hazardous substances, which are then integrated into the natural biogeochemical cycles. Some microorganisms, mainly the members of family Actinomycetes, were found with the capability of transforming and degrading the polluting agents. In this study, three different Nocardia species with the ability to biodegrade organic and inorganic compounds were isolated from soil in Isfahan province.
Materials & Methods: The soil samples were collected from the hospital environments. Isolation process was done according to the standard methods. The identification and characterization of the isolates were based on the conventional and molecular methods, including direct sequence analysis of almost full length of 16S rRNA gene.
Results: Almost, the complete 16S rRNA gene sequences of the strains under study revealed that the isolates coded as NR6, NR17, NR18, NR25, NR26, and NR28 were the strains of N. cyriacigeorgica; NR7, NR34, and NR50 were the strains of N. coubleae; and NR4 was the strain of N. otitidiscaviarum. The relationship between the isolates under study and standard strain of Nocardia was supported by a phylogenetic tree of 16S rRNA gene.
Conclusion: In this study, 10 Nocardia strains with the capability of biotransforming polluting agents were isolated from the hospital environments. It was the first study conducted on the isolation and characterization of Nocardia strains, with the capability of degrading polluting agents, from Iranian hospitals. This study can be considered as a pioneer to develop a new insight about the study of microbial diversity in Iran using an applied approach to deal with environmental challenges.
, Arastoo Badooei, , ,
Volume 6, Issue 2 (11-2015)
Abstract
Amides are toxic, mutagenic and carcinogenic compounds. Amidase-producing bacteria eliminate or convert these compounds to their correspond acid. This study was carried out to investigation the Benzamide degradation by Achromobacter strains, which isolated from the waste of the city of Kerman. These strains were enriched in MM1 medium with benzamide 1% . The best strains were selected in MM1 agar media sublimentated with benzamide (1%) and bromothymol blue, as pH indicator. In total of 7 benzamide hydrolysing bacteria two of them, AB37 and FA1, were identified as predominant strains. The medium optimization showed that glucose, peptone, Ca2+ and pH 7.0 enhanced enzyme production, compared to the control. Enzyme production was enhanced in the presence of glucose and calcium about 3.0 and 2.6 folds, respectively. Hydrolyzing potential of benzamide by AB37 strain showed that the maximum benzamide hydrolyzing was 1.79 after 15 h of incubation. Based on the biochemical and test 16S rRNA gene approaches these strains were identified as Achromobacter xylosoxidans and Achromobacter Spanius. Results showed that these isolates were able to produce amidase and also were able to degrade benzamide. Therefore, the evaluation of applied potential of these strains for bioremediation of industrial and agricultural wastewater is recommended.
, Mehdi Hassanshahian, ,
Volume 8, Issue 2 (10-2017)
Abstract
Crude oil is comprised of four groups: Saturates Aromatics, Resins and Asphaltenes. Oil pollution has irreversible effects on marine ecosystems. Therefore paying attention to oil pollution and the management of the ports is very important. Biodegradation of oil derivatives is more effective, more powerful and more economically efficient method for remediation in polluted sites rather than physicochemical methods. In this study, for isolation of crude oil degrading bacteria, seawater and mussels were collected from Persian Gulf. Enumeration of bacteria were done in collected samples. Isolated bacteria were identified by biochemical and molecular tests. Crude oil biodegradation for each strain was assessed by spectrophotometer and Gas Chromatography (GC). The results of this study show that the quantity and biodiversity of heterotrophic and crude oil degrading bacteria in Crassostrea gigas mussels was higher than surrounding environment (seawater). Eleven crude oil degrading bacteria were isolated from Persian Gulf, 7 strains were identified biochemically and 2 strains were selected on the basis of higher degradation. These isolated strains were identified as Shewanella and Alcanivorax. The half percentage of oil was removed by these strains in 15 days of incubation. These bacteria could be used for cleanup oil-polluted marine areas after more research and field observation.
Z. Montazer, M.b. Habibi-Najafi , M. Mohebbi, A.r. Oromieyee ,
Volume 10, Issue 2 (7-2019)
Abstract
Accumulation of polyethylene (PE) wastes has become a major environmental problem. The objective of this research was to assess the potential for microbial degradation of sun-treated low-density PE as a natural way to eliminate PE wastes in semi-industrial condition. Low-density polyethylene (LDPE) films were exposed to one month of sun radiation treatment and then cultured with two PE-degrading bacteria (Sphigobacterium moltivorum IRN11 and Delftia tsuruhatensis IRN27) in aerobic bioreactors over 100 days. Weight loss percentage of the PE and the culture pH were measured. Also, Changes in the chemical structure of the LDPE were assessed by FT-IR and surface erosion and microbial layer formation by bacterial activity was observed by Scanning Electron Microscopy. Partial increases in the culture pH were recorded during the incubation period. The weight loss percentage for T-LDPE samples cultured with Sphigobacterium moltivorum IRN11 and Delftia tsuruhatensis IRN27 was 3.31%±0.013 and 3.98%±0.025 in TLDPE samples, respectively, and functional carbonyl-groups in the TLDPE samples decreased significantly due to bacterial hydrolysis. SEM images showed the different microbial layer formation on sun-treated low-density polyethylene (T-LDPE) for both bacteria. Our results suggest that exposure of LDPE to sun radiation had a significant effect on biodegradation of Ld-PE films and that the two bacteria tested were able to enhance the biodegradation the T-LDPE.
Volume 15, Issue 2 (7-2015)
Abstract
Abstract: Wastewater contaminated by petroleum compounds includes a wide range of hydrocarbons with different concentrations. Due to high amounts of toxic multiple cyclic aromatics, this type of wastewater may cause significant damages to water resources and human health, which have to be treated before discharging to the environment. Different processes have been applied for treating these kinds of wastewater. The most conventional systems are biological processes especially activated sludge that is being used in the most of the Iranian refineries. In recent years, biofilm processes have been replaced for treating different types of wastewaters because of bulking and foaming problems in the suspended systems. Due to the least deficiencies and restrictions, these processes have been proved as a reliable method for removal of wastewater pollutants. Therefore, in this study, the capability of treating petroleum wastewater was investigated using Moving Bed Biofilm Reactor (MBBR). This study was conducted in a lab-scale batch plastic rectangular cube pilot (L: 24 cm, W: 17 cm, H: 9 cm). To get a compound similar to petroleum effluent of Tehran Refinery, the mixture of gasoline (C16 - C20) and crude oil (C8 - C37) by the ratio of 1 to 2 was prepared. At first, sewage sludge was adapted with hydrocarbon compounds at COD equal to 100 mg/L (or TPH of 27.4 mg/L). Then petroleum hydrocarbons was injected to the reactor with a COD range of 200 to 2500 mg/L (TPH of 52 to 400 mg/L); and COD and TPH removal efficiency was measured at different retention time. Also the dominant mechanism, kinetic of biological reactions, the effect of suspended microorganisms and carrier filling ratio were studied. The highest COD removal efficiency of 85 percent was obtained at influent COD= 1000 mg/L, HRT= 72 hr and filling ratio = 50 percent. The removal trend of organic compounds from the end of adaptation stage (COD= 100 to 1000 mg/L) at resident time of 8, 12 and 24 hours has been varied between 62 and 48 percent. TPH removal efficiency in aforementioned range, followed a smooth trend; so that in HRT= 72 hr, the removal efficiency reduced from the initial 84 percent at TPH= 50 mg/L to 75 percent at TPH= 400 mg/L. The ratio of COD to input TPH was 3.82 and the range of ratios of COD to output TPH at resident times of 24, 48 and 72 hours were 3.09 - 4.80, 9.00 - 13.89 and 10.80 - 15.63, respectively. The results have shown that Grau and Stover- Kincannon were the best models for describing the biological kinetic data. The results have shown that MBBR system is a proper method for treating petroleum hydrocarbons, due to adequate ability to decomposition of these kinds of pollutants.
Volume 15, Issue 4 (12-2015)
Abstract
With less availability of land and loss of crops by pest, the use of pesticide such as Atrazine is increasing significantly. Atrazine is a member of s-triazine group herbicides and is a probable human carcinogen (Group 2B). Atrazine is resistant in the environment and, as a result, causes serious environmental problems. Moreover, it penetrates through the surface and subsurface water bodies as well as groundwater due to its excessive usage and high persistence and mobility. In general, several methods, such as adsorption, incineration, oxidation-reduction, photolysis, hydrolysis, dehalogenation, reverse osmosis, and chemical degradation, are available for removing Atrazine from contaminated water and wastewater; however, these methods are very costly, have many performance problems, produce a lot of toxic intermediates which are very harmful and dangerous, and cannot completely mineralize Atrazine. Biodegradation is an economically viable technology which leads to complete degradation and mineralization of Atrazine and produce simple compounds, such as carbon dioxide, water, nitrogen, and organic materials. Biological methods having enzymatic system that which is Atrazine used as carbon, nitrogen and energy source and completely mineralization occur, also submerged aerated filters to their treatment mechanism greatly contributed to reduce treatment cost. In this study potential of Biological Aerated Filter (BAF) in Atrazine removal from aquatic environment, at 4 concentration of Atrazine and 3 hydraulic retention times (HRTs) was evaluated. Based on the results Atrazine degradation potential of the mixed aerobic consortium was evaluated under various Atrazine concentrations and HRTs. It was shown that maximum efficiency in Atrazine and Soluble Chemical Oxygen Demand (SCOD) removal was 97.9% and 98.3%, respectively. Also stover-kincannon model have very good fitness (R2 > 99%) in loading Atrazine in this biofilter. Submerged aerated filter, a good performance in the removal of toxic and sustainable organic. High degradation rate of Atrazine at comparatively high Atrazine concentration might be due to the effect of concentration gradient. At high concentration gradient, the pollutant has a higher chance to be exposed to and/or penetrate through the cell which is essential for biodegradation. Co-metabolic process is used for bioremediation of most persistence contaminants, such as Atrazine. In co-metabolic processes, by utilizing primary carbon source or nitrogen source, microbes produce enzymes or cofactor during microbial activities which are responsible for degradation of the secondary substrates (toxic compounds, Atrazine). Also, the contaminants degrade in this process in order to trace concentrations. Cometabolism process was effective in Atrazine degradation process and aerobic mixed biofilm culture was observed to be suitable for the treatment of Atrazine from aqueous solutions. The present study investigated the ability of an BAf to remove Atrazine from aqueous environment. The BAF was operated at 3 different aerobic retention times in order to determine the optimum retention time for the highest Atrazine and COD removal.
