Sharif Digital Repository

This study deals with the large-scale production of biosurfactant from soybean oil soapstock by Pseudomonas aeruginosa MR01. The production of biosurfactant was carried out in a newly designed bioreactor equipped with recycling flow under three operational conditions. Kinetic studies were conducted at both shake flask and 5-L bioreactor scales during fermentation in a soapstock medium. Mathematical equations were developed to model the kinetic patterns at both scales. RESULT: Statistical analyses demonstrated the goodness of fit, with regression r-squared, R2, between 0.97and 0.99 for different models. Furthermore, biosurfactant concentration in the bioreactor including the recycling flow,... 

Biosurfactants are microbial substances which influence interfacial tension. The kinetic study was carried out for Pseudomonas aeruginosa MR01 during biosurfactant production in a two-phase liquid-liquid batch fermentation system. The maximum rhamnolipid concentration (Pmax) and the yield of biosurfactant per 1 biomass (YP/X) in a 5-L bioreactor containing soybean oil medium were found to be approximately 20.9 g.L and 3.1 g.g-1, respectively. Previously reported kinetic models in aqueous systems, three-parameter Gompertz, 2 Luedeking-Piret and Mercier equations, demonstrated adequate goodness-of-fit (r >0.9) to kinetic data recorded for biomass growth, nitrate consumption and rhamnolipid... 

The effect of an efficient biosurfactant produced from Pseudomonas aeroginosa MR01, a bacterial strain isolated from oil excavation areas in southern Iran, on the recovery of residual oil trapped within carbonate rocks, was investigated. In a core holder set-up, bearing a number of limestone-and dolomite-containing core samples, biosurfactant flooding resulted in oil recoveries as large as 20% to 28% Residual Oil (R.O). Biosurfactant injection in less permeable rocks in a range of 0.5 to 32 md was more successful, in terms of oil production. In the case of the least oil recovery via biosurfactant flooding, incubation of the core with a biosurfactant solution at reservoir conditions,... 

Rhamnolipids are the most common biosurfactants and P. aeruginosa strains are the most frequently studied microorganisms for the production of rhamnolipids. Eco-friendly advantages and promising applications of rhamnolipids in various industries are the major reasons for pursuing the economic production of these biosurfactants. This study shows that cultivation of P. aeruginosa MR01 in medium contained inexpensive soybean oil refinery wastes which exhibited similar levels and homologues of rhamnolipids. Mass spectrometry indicated that the Rha-C10-C10 and Rha-Rha-C10-C10 constitute the main rhamnolipids in different cultures of MR01 including one of oil carbon source analogues. Moreover,... 

Background: Recently, concerns have been raised regarding the environmental and public health safety of azo dyes, the most widely used synthetic dyes. The membrane technique has been introduced as one of the efficient methods for dye removal treatments. Polyvinylidene fluoride (PVDF) membrane manipulated by surfactants was studied for removal of the azo dye, carmoisine. Methods: PVDF membrane was prepared via non-solvent-induced phase separation (NIPS) and used to remove the azo dye, carmoisine. Three nonionic surfactants including Tween 20, Tween 60, and Tween 80 were used individually as additives in casting solutions to improve PVDF membrane properties. Results: Fourier-transform infrared... 

A bacterial strain was isolated and cultured from the oil excavation areas in tropical zone in southern Iran. It was affiliated with Pseudomonas. The biochemical characteristics and partial sequenced 16S rRNA gene of isolate, MR01, was identical to those of cultured representatives of the species Pseudomonas aeruginosa. This bacterium was able to produce a type of biosurfactant with excessive foam-forming properties. Compositional analysis revealed that the extracted biosurfactant was composed of high percentages lipid (∼65%, w/w) and carbohydrate (∼30%, w/w) in addition to a minor fraction of protein (∼4%, w/w). The best production of 2.1 g/l was obtained when the cells were grown on... 

Azo dyes are common dye groups widely used in different industries. Industrial effluents which contain these dyes pervade water resources and have various known and unknown physiological effects on living organisms. In this study, methyl red (MR) was proposed as a model azo dye to examine the capability of Saccharomyces cerevisiae ATCC 9763 for cleavage of the azo bond leading to decolourization. The spectrophotometry method showed that complete decolourization occurred statically during ≃12 h and this time reduced to several minutes less than 10 min where cell mass increased. Thin layer chromatography (TLC), mass spectroscopy and Fourier transform infrared (FTIR) confirmed degradation of... 

In the present study, an aqueous root-extract of Acanthophyllum laxiusculum (AREAL) was evaluated for phenanthrene removal from two samples of contaminated soil. AREAL showed a linear solubilization enhancement for phenanthrene with a weight solubilization ratio of 0.05. Batch soil washing experiments caused the removal of phenanthrene with efficiencies of 96.7% and 78% from soils with 0.78% and 2.73% organic carbon, respectively. Desorption kinetics of phenanthrene exhibited a twophase pattern, namely, a rapid release as the initial phase and a slower removal as a subsequent phase. A two-compartment exponential model could adequately represent the two phases of the kinetic pattern of... 

The comparative study of Active Screen Plasma Nitriding (ASPN) treatment of two Finemet-type alloys with the compositions of Fe73.5Si 13.5B9Nb3Cu1 and Fe 77Si11B9Nb2.4Cu0.6 was investigated in different temperatures ranging from 410°C to 56°C. Differential Scanning Calorimetry (DSC), X-Ray Diffractometery (XRD), Atomic Force Microscopy (AFM), Scanning Electron Microscopy (SEM), electrical resistivity, microhardness measurements and magnetic characterization by a Vibrating Sample Magnetometer (VSM) were utilized to characterize the treated samples. The comparison of the DSC data for the alloys suggested that the smaller amount of Nb as a growth inhibitor shifted the crystallization... 

Azo dye degradation in wastewater treatment is a subject which has garnered the attention of many research studies. In this study, an innovative approach, namely, an integrated system of five batches (ISFB), was developed to investigate the capability of Saccharomyces cerevisiae ATCC 9763 for continuous degradation of methyl red as a representative azo dye. Toward this end, an expanded immobilized microbial bed (EIMB) reactor was established with a bed of encapsulated yeast cells in sodium alginate. EIMB reactor was run in two modes, single batch and ISFB. Moreover, durability of the microbial cells was evaluated by repeating the continuous decolourization eight sequential times in EIMB at... 

The nanocrystallization process of amorphous Fe73.5Si13.5B9Nb3Cu 1 was investigated by active screen plasma nitriding (ASPN) treatment at temperatures ranging from 410 °C to 560 °C for 3 h in two gas mixtures of 75% N2-25% H2 and 25% N2-75% H2 at 5 mbar atmosphere. The amorphous ribbons were then annealed under vacuum at the same time and temperatures mentioned above. The structure of the samples was analyzed using various techniques such as X-ray diffraction (XRD), atomic force microscopy (AFM) and differential scanning calorimetry (DSC). Microhardness measurements, electrical resistivity and Vibrating Sample Magnetometer (VSM) were used to study mechanical, electrical and magnetic...