Sharif Digital Repository

Biodegradation of petroleum hydrocarbons in salt medium (SM) containing sea water by Pseudomanas sp. was investigated. Different oil hydrocarbons such as n-decane, benzene, naphthalene, paraffin, paraffin + vaseline, paraffin + kerosene, and fuel oil were used as carbon sources. Cell growth (OD) and COD were measured for evaluation of oil biodegradability. The effect of inorganic and organic nitrogen sources on COD removal revealed a 95% and 75% reduction of COD for inorganic and organic nitrogen sources, respectively  

A laboratory scale study using a modified rotating biological contactor (RBC) was constructed to assess aerobic treatment of toluene, a typical aromatic hydrocarbon. The RBC consisted of 72 parallel discs rotating in a reservoir and was arranged in three stages, i.e. 24 discs oriented in each stage. An artificial wastewater containing toluene was fed to the RBC, inoculated with an enriched culture from petrochemical sewage. The rotation of the discs and the recycling time ensured good mixing of the bulk liquid and resulted in a regular biofilm thickness. Toluene removal was measured by COD measurement and GC. The effect of initial toluene concentration on toluene biodegradation showed a zero... 

This study presents the removal performance of phenol in a three-stages cross flow laboratory-scale rotating biological contactor (RBC). The impact of major process and operating variables, such as input hydraulic loading (HL), input COD loading, and temperature of wastewater on the total removal efficiency of the system were examined. It was observed that the phenol removal performance worsened when the HL increased, and optimum total phenol removal efficiency of 99.9% was observed at loading of 4 × 10-3 m-3 m-2 per day and COD concentration of 800 mg dm-3. On the basis of overall treatment of phenol containing wastewater in the RBC, the optimal removal performance was noted at the end of... 

Biodegradable thermoplastic films suitable for use in food packaging were produced. These films were mainly based on thermoplastic starch. The major task included research into thermal conversion of starch in a compression molding process and also under high shear conditions in an extruder in the presence of suitable plasticizers. The destruction of crystalline structure resulted in amorphous structure with thermoplastic properties. Films were rather transparent but slightly brown in color and had a specific smell. The films showed sufficient plasticity and acceptable tensile strength and elongation. The effect of plasticizer content on the final properties of the film was investigated. The... 

Optimization based on appropriate parameters can be applied to improve a process. Mazut degradation as a critical issue in environment requires optimization to be efficiently done. To provide biodegradation conditions, experiments were designed on the least interactions among levels of parameters consisting of pH, Tween 80, glucose, phosphorous source, nitrogen source, and time. Kinetic constants and biomass were calculated based on 16 assays, designed using Taguchi method, which constructed various mazut biodegradation conditions. Kinetics of mazut degradation by newly isolated bacteria Enterobacter cloacae closely followed second order kinetic model. Results of the 16 experiments showed... 

Recently, the use of biodegradable polymers became the applicable solution to reduce the environmental concerns, which are created by plastic wastes as well as restrictions of petroleum-based synthetic polymers. By this point of view, polylactic acid (PLA) as a biodegradable and bio-based polymer is resolving both aforementioned issues. While, the high cost of PLA and its slow biodegradation rate make researchers to blend it with a faster one, for instance, thermoplastic starch (TPS). Adding TPS into PLA can influence on the morphological structure, thermal stability, and biodegradability. In this study, the well-tuned co-plasticized TPS via sorbitol/glycerol mixture was melt mixed with PLA... 

Orthopaedic implant-associated infections are one of the most serious complications in orthopaedic surgery and a major cause of implant failure. In the present work, drug-eluting coatings based on chitosan containing various amounts of vancomycin were prepared by a cathodic electrophoretic deposition process on titanium foils. A three-step release mechanism of the antibiotic from the films in a phosphate-buffered saline solution was noticed. At the early stage, physical encapsulation of the drug in the hydrogel network controlled the release rate. At the late stage, however, in vitro degradation/deattachment of chitosan was responsible for the controlled release. Cytotoxicity evaluation of... 

Azotobacter beijerinckii DSMZ 1041 strain was used for production of polyhydroxybutyrate (PHB) and the optimum glucose concentration, as the carbon source and ammonium chloride, as the nitrogen source were obtained 60gr/lit and 0.5gr/lit respectively. The resulting optimum PHB production was investigated 2.95gr/lit. The obtained yield of PHB with respect to glucose (Yp/s) and PHB productivity (Qp) were 0.202 g/g and 0.123 g/lit.hr, respectively. The response surface methodology (RSM) was used to verify the accuracy of the designed experiments. azotobacter beijerinckii microorganism from Deutsch sammlung von microorganismen und zellkulturen(DSMZ) bank is used for production of Poly Hydroxy... 

Batch cultures of Azohydromonas lata DSMZ 1123, Hydrogenophaga pseudoflava DSMZ 1034, Cupriavidus necator DSMZ 545 and Azotobacter beijinckii DSMZ 1041 were investigated for producing the intracellular bioplastic poly-•-hydroxybutyrate (PHB). The effects of temperature, seed age, type of carbon sources and the agitation rate on the production rate of PHB were investigated using four mentioned spices. The optimized shaking rate, temperature and seed age were obtained 250 rpm, 30°C and 15 hrs for H. pseudoflava DSMZ 1034 and A. beijerinckii DSMZ 1041 and 18 hrs and 24 hrs for A. lata DSMZ 1123 and C. necator DSM 545, respectively.The effect of carbon sources including glucose, fructose, whey... 

Objective: a convenient numerical model has been developed to predict release profile of different types of agents from bulk biodegrading polymer microspheres, including magnitude methods are less accurate than analytical methods. Usually, this study used analytical solutions for the model and compared the analytical results with numerical solution and experimental data. Methods: The objective drug controlled release profiles were modeled based on a four-phase pattern. Then, a specific formulation was considered based on Fick’s second law. After calculating various parameters, the equations were solved using an analytical method. Results: Comparison results showed that analytical solution... 

Micro flora of the effluents from a dairy factory in Tehran(Pegah Dairy Processing Plant) were isolated and screened for their ability to reduce the organic matter content and COD of the effluents. 10 bacteria were selected due to reduction in COD content from the 4th to 6th day of incubation at 30 °C and pH =11. Highest COD reduction were obtained by two isolates, BP3 and BP4, 70.7 % and 69.5 %, respectively (The initial COD concentration was 3000 mg/l and reduced to 880 and 920 mg/l).After optimization of the condition for test organisms, big reductions in COD, carbohydrate, fat and protein content of the effluents were observed by BP3 up to 84.70 %, 98 %, 45.30 % and 53 %, respectively... 

Mazut as a source content of various hydrocarbons is hard to be degraded and its cracking could turn mazut into useful materials. Nevertheless degradation of mazut by routine methods is too expensive but application of indigenous microorganisms as biocatalysts could be effective and important to lower the costs and expand its consumption. Mazut biodegradation can be improved using various strategies; Therefore in this study newly isolated strain Enterobacter cloacae BBRC 10061 was used in a method of gradual addition of mazut into medium and its results were compared with simple addition method. To investigate degradation of mazut by BBRC 10061, influence of increase of mazut concentration... 

The biodegradability rates of two different kinds of polyethylene bonded with corn and potato starch are studied in this paper. While it is usual to use soil as the environment for biodegradation, an aerated sludge tank was used in this studywhich offers a richermicrobialmediumand increases the rate of biodegradation. The biodegradability is determined by two ways: first, comparing differences in the weight change of two samples, one placed inside distilled water and the other placed in aerated sludge tank. Second test for biodegradation is by examination of FTIR spectroscopy. Through FTIR spectroscopy, the biodegradability rate and reduction in some of the existing bonds in polymer before... 

Highly conductive polypyrrole/graphene (PYG) nanocomposite was synthesized with chemical oxidation process via emulsion polymerization and used for the preparation of novel porous conductive gelatin/chitosan-based scaffolds. The effect of PYG loading on various properties of scaffolds was investigated. The obtained results indicated that by introducing PYG into the polymeric matrix, the porosity and swelling capacity decreased while electrical conductivity and Young's modulus demonstrated increasing trend. The in vitro biodegradation test revealed that pure gelatin/chitosan matrix lost 80% of its weight after six weeks in the presence of lysozyme whilst the biodegradation rate was... 

The present study was carried out to evaluate the degradation efficiency of benzene, toluene, and xylene (BTX) by isolated bacteria from various petroleum-hydrocarbons contaminated sites. Five isolated bacteria were selected for testing BTX biodegradation from liquid culture media. Each of these bacteria was able to degrade BTX but with different efficiencies. Maximum biodegradation efficiency for benzene (more than 70 %) was obtained by Gram-positive coccobacillus, Gram-positive coccus and Gram-negative bacillus bacteria, for toluene (60 %) and xylene (70 %) by Gram-positive coccobacillus and Gram-negative coccobacillus. It was found that the presence of xylene in the substrate mixture...