Papers by Keyword: Biodegradation

Abstract: Improper disposal of commodity plastics such as polyethylene (PE) in the environment causes land pollution and soil infertility. It is unsightly and strongly threatens plant and animal life. The current effort describes the bacteria-mediated biodegradation of polyethylene by Serratia marcescens marcescens (SM) without prior exposure to thermo-oxidative aging. This study further describes the mechanism involved in the biodegradation of PE, in which a carbonless medium containing essential minerals and vitamins and powdered PE, were placed in the presence of overnight cultures of SM. The samples were incubated at 30°C, centrifuged at a speed of 141 revolutions per minute (rpm) in a rotary shaker for ten weeks in order to observe the degradation process. The effects of cell-free supernatants (from the SM cultures) upon the degradation of sterile PE are elucidated. The results show that the supernatants from SM degrade PE faster than the bacteria, with a 37.5 percent of degradation rate within a month. The SEM micrographs suggest that the biodegradation of polyethylene involves the formation and coalescence of microvoids. The DSC results revealed that the feeding activity of SM is mostly favored at the crystalline region due to its high energy.

Abstract: The key objective of present study was to find out a novel and innovative strategy to tackle problem of cyanide and metal-cyanide pollution thereby leading to indirect mitigation of global warming. Studies were performed to test the feasibility of treating aqueous waste containing free cyanide (CN^-) and copper-cyanide {Tetracyanocuprate - TCC, [Cu (CN)₄]^-2} using microalgae Scenedesmus sp. that was isolated by enrichment culture technique under alkaline conditions. Results revealed that microalgae Scenedesmus sp. was capable of detoxifying cyanide and TCC (10-25 mg/l as CN^-) with an efficiency of >99% under aerated, static and illuminated conditions within a period of 48-96 h. Process parameters like pH (7-11), temperature (20-45°C), initial cell density (10³-10⁶ cells/ml) and varying concentration of cyanide and TCC (5-50 mg/l as CN^-) were optimized. Of the total copper ions released during biodegradation of TCC, 37% was adsorbed on the cells, while 67% was accumulated by Scenedesmus cells.

Abstract: This paper attempts to propose an innovative strategy/model for the recovery of precious metal like silver from e-waste by employing combined technologies. Firstly, silver is leached using free cyanide from electronic scrap thereby forming silver-cyanide complex. In the second step, silver-cyanide is removed using biosorption using passive Eicchornia roots powder biomass. Lastly, the residual silver-cyanide remaining after biosorption is biodegraded using live heterotrophic bacterial consortium. Feasibility study showed that the overall system strategy worked efficiently for the management of e-waste.

Abstract: Some unfortunate accidents of large amount of oil hydrocarbons have been reported in Mediterranean Sea which has caused severe environmental damage to the area. To safeguard the Libyan coastline and marine ecologysince thousands of human activity such as fishing largely depends on the healthycoastal environment.Twenty crude oil-degrading bacterial isolates were obtained from oil-contaminated sites at Al Hariga Oil Terminal and Nafoora Oilfield. Based on a high growth rate in crude oil and hydrocarbon degradation efficiency, two isolates were selected from the twenty isolates for further analysis. The nucleotide sequence of 16S rRNA gene showed that these isolates are likely Pseudomonas aeruginosa andKocuriapastrius. One of the isolates is a potential Gram-negative Pseudomonas bacterium based on petroleum hydrocarbon degradation efficiency and potent emulsifying activity; thus, this isolate is identified as P. aeruginosa NAF1; the other isolate K. pastrius SAR3 is identified as a Gram-positive bacterium. Corn steep liquor (CSL) and solid waste date (SWD) were used for an in situ molasses technique to enhance bacterial growth and biodegradation efficiency. P. aeruginosa NAF1 exhibited 70% and 76% crude oil degradation in 0.2% (w/v) CSL and SWD in 28 d, respectively. Likewise, K. pastrius SAR3 yielded 68% and 70% crude oil degradation in 0.2% (w/v) CSL and SWD in 28 d, respectively.

Abstract: The purpose of this work was to produce nanocomposites of polylactic acid with oph-POSS (octaphenyl-Polyhedral Oligomeric Silsesquioxanes)-based biodegradable polyester and study morphology, thermal stability and degradation property. Oph-POSS was synthesized via limited-hydrolytic condensation of phenyl trimethoxysilane catalyzed by tetramethylammonium hydroxide. By adding different mass fractions of oph-POSS into the PLA matrix, oph-POSS/PLA nanocomposites were successfully prepared by the solution casting method using chloroform as solvent. SEM(scanning electron microscopy) observations indicated that oph-POSS were homogeneously dispersed in the PLA matrix. The biodegradation rate of oph-POSS/PLA composites was higher than that of neat PLA, moreover, the degradations of neat PLA and oph-POSS/PLA composites underwent the surface erosion mechanism. It was found that the existence of oph-POSS enhanced thermal stability slightly of nanocomposites relative to neat PLA; however, the thermal degradation mechanism of PLA remained unchanged.

Abstract: Magnesium-zinc (Mg-Zn) alloys are strong candidates as medical implant materials due to their good biocompatibility and relatively high strengths. To manipulate the degradation of Mg-Zn alloy in the human body, a plasma electrolytic oxidation (PEO) treatment was applied to Mg-10%wt. Zn in this study because it produces a coating that is non-harmful to the human body and the process is inexpensive and environmentally friendly. Potentiodynamic polarization corrosion tests, performed in a simulated body fluid (Hanks’ Balanced Salt Solution) were applied to the coated and uncoated Mg-Zn samples. The results of the testing showed that the coated Mg-Zn exhibited higher corrosion resistance than the substrate. With the PEO coating thickness of 7.2 microns, the corrosion current density was reduced by 1.00 μA/cm² from the uncoated Mg-Zn respectively, indicating a significant reduction in the degradation rate between pure Mg-Zn and coated Mg-Zn from 7.0 to 3.7 kg/year. A pin-on-disc tribometer was employed to measure the coefficient of friction (COF) for the coated and uncoated Mg-Zn samples, lubricated with and without Hanks’ solution. The measured COF of the coated sample was very low (averaging to be about 0.22 under the lubricated condition) and comparable to that of the substrate which exhibited an averaged COF of 0.13 under the lubricated condition.

Abstract: The kinetic of microbial growth and substrate utilization can be used to predict the fate and behavior of contaminants like PAHs in the environment through appropriate models. Further kinetic study results are useful in evaluating and weighing suitable treatment option for remediation and clean up of contaminated sites.. In this research a mathematical model for biodegradation of PAHs using isolated bacteria from municipal sludge was studied.. The model was developed using the Monod equation.. Results showed that the remaining PAHs in all samples decreased within time.

Abstract: Paper wastes accumulating in the environment are posing an ever increasing ecological threat. This study aimed to isolate soil bacteria closely associated with the bacteria degrading waste paper. A total of six soil samples were collected from dumped soil hostel garden at Universiti Teknologi MARA, Shah Alam. Bacillus, Aspergillus and Micrococcus species were found to be the most widely distributed on the entire sample taken. Six cultures were screened for the ability to degrade cellulose. Bacillus was identified as only bacteria isolated that can degrade paper at highest production of glucose compared to others. The efficacy of microbes in the degradation of paper was analyzed in broth culture fermentation within 7 days incubation. This work reveals that Bacillus subtilis, Bacillus spp and Micrococcus spp posses great potential to degrade paper. In contrast, Acinetobacter spp react very slowly in degrading the waste.

Abstract: The application of photodegradable polyethylene is increasingly important for agricultural uses due to its ability to degrade after suggested shelf life and to counter measure pollution issue caused by conventional polyethylene films. The photodegradable polyethylene (PE) mixtures were formulated with added polypropylene (PP) and photodegradant (RM master batch) and tested in oil palm seedlings cultivation. PP is known to have photodegradable ability and RM master batch is proven to induce photo degradation of polyethylene. Thus, the mixture of these three components according to different ratios was processed into agricultural plastic films. There are four formulations that are tested in this study, namely T1 (80% PE:20% PP:5% RM master batch), T2 (70% PE:30% PP:5% RM master batch), T3 (80% PE:20% PP:3% RM master batch) and T4 (70% PE:30% PP:3% RM master batch). All formulations except control sample were added with photodegradant to impart degradation reaction and compatibiliser was also affixed to allow coalesce between polyethylene and polypropylene. Carbon black was added 0.5% into the formulation as for poly bags application, dark environment of soil is crucial for root development and growth. Penetration of sun light into the planting soil could commence development of shoot instead of root growth. All four formulations showed observable morphological changes on microscopic images on the surfaces after being used in oil palm nursery. From the study, it is shown that T1 and T3, with 20% of additional polypropylene had demonstrated clear surface disintegration when viewed microscopically. The addition of 3% and 5% of photodegradant into the formulations did not show any expressive difference thus suggesting that 3% of photodegradant is the optimum amount to induce photo degradation.

Abstract: The low degradability behaviour of plastics is an important environmental problem. The end-use of plastic creates waste-disposal problems as these plastics do not readily or naturally degrade and gives severe effect when plastic-waste requires more time to break down. However, as the bio-polymer industries have advanced, biodegradable plastic is being presented as a high promising solution to the environmental problem over the conventional non-biodegradable plastics. As one of the great innovation products in bio-polymer industries, biodegradable plastic can potentially lessen the volume of solid waste and reduce the need for waste dumping sites. Whilst, biodegradable plastic also offers the outstanding properties to resist the brittleness and resistance towards heat. This paper review the potential of biodegradable plastics made from petrochemical-polymers blended with starch, including polyethylene (PE), polycaprolactone (PCL), polyvinyl alcohol (PVOH) polypropylene (PP) and polyvinyl chloride (PVC).