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Farzaneh Vahabzadeh,Mohamad Hajar 한국화학공학회 2016 Korean Journal of Chemical Engineering Vol.33 No.4
A laboratory-scale stirred basket reactor (SBR) was constructed to study the synthesis of an n-butyl oleate ester using Novozym 435. An ester yield of approximately 98% was obtained after 6 h using an equimolar substrate ratio, 3.5 g of enzyme, a reaction temperature of 40 oC, and an impeller speed of 200 rpm. The kinetic data were modeled as a ping-pong bi-bi mechanism using a non-linear regression technique. Statistical analysis of the results showed that a model that incorporated the inhibitory effect of n-butanol yielded the best fit with the following parameters: Vmax=24.8mmol L−1 min−1, Km, oleic acid=190.8mM, Km, n-butanol=544.7 mM, and Ki, n-butanol=158.3mM. Mass transfer effects on the enzyme kinetics were also studied, and the absence of internal and external diffusion limitations on the reaction in the SBR was confirmed by considering calculated values of the Thiele modulus and the Damkohler number. Novozym 435 exhibited satisfactory performance in repeated-batch experiments using SBR.
Ethanethiol Degradation by Ralstonia eutropha
Mahsa Sedighi,Farzaneh Vahabzadeh,Seyed Morteza Zamir,Abbas Naderifar 한국생물공학회 2013 Biotechnology and Bioprocess Engineering Vol.18 No.4
In the present study, a pure culture of Ralstonia eutropha was used to degrade gaseous ethanethiol. Ethane thiol at various initial concentrations ranging from 115 to 320 mg/m3 was degraded almost completely within 120 ~168 h, while at higher concentrations up to 452 mg/m3,removal efficiency declined. It was likely that ethanethiol was used as the source of energy by R. eutropha, since no clear increase in the biomass concentration was observed. Kinetic data of ethanethiol bidegradation could be fitted using the Monod model. The kinetic parameters were qm =0.23 (mg ethanethiol/g biomass/h), and Ks = 1.379 (mg/L). The mineralization pathway of ethanethiol through sulphate,as the detected product, and the energy production were discussed in some detail.
Alireza Monazzami,Farzaneh Vahabzadeh,Abdolreza Aroujalian,Azadeh Mogharei 한국화학공학회 2018 Korean Journal of Chemical Engineering Vol.35 No.4
With the use of β-cyclodextrin (β-CD), Pickering-type diesel-in-water emulsions were prepared based on the inclusion complex formed between diesel and β-CD which acted as an emulsifier. By using the artificial neural network (ANN), the rheological behavior of the emulsions was characterized using three input variables: diesel-to-water ratio, β-CD concentration, and shear rate and one-output variable as shear stress. Gradient descent (GD), conjugate gradient (CG), and quasi Newton (QN) were used as three different methods in the feed-forward back-propagation algorithm for network training. Hyperbolic tangent sigmoid and pure linear were the transfer functions used for transforming information between input and output through one hidden layer containing ten neurons. By dividing the experimental data into three sets of training, validation, and testing, the QN method in predicting shear stress was found to have performed better than the other two network learning techniques (R2=0.994 and MSE=0.006).
Bita Dadpour,Maryam Vahabzadeh,Babak Mostafazadeh 대한중환자의학회 2020 Acute and Critical Care Vol.35 No.1
Background: The optimal goal of naloxone infusion in intensive care units is to ameliorate opioid-induced side effects in therapy or eliminate the symptoms of opioid toxicity in overdoses. Accurately monitoring and regulating the doses is critical to prevent adverse effects related to naloxone administration. The present study aimed to compare treatment outcomes when using two methods of intravenous naloxone infusion: an infusion pump or the standard method. Methods: This study involved 80 patients with signs and symptoms of opioid overdose. The patients were randomly assigned into two groups with respect to intravenous infusion of naloxone by either an infusion pump or the standard method. Results: Comparison of study parameters between the two groups at 12 and 24 hours after intervention showed significantly more compensatory acid-base imbalance in the naloxone infusion pump group. In the group that received naloxone by pump, only one patient experienced withdrawal symptoms, but withdrawal symptoms appeared in 12 patients (30.0%) in the standard intravenous infusion group within 12 hours and in seven additional patients (17.5%) within 24 hours of intervention. In the group receiving pump-based naloxone infusion therapy, no another complications were reported; however in the standard infusion group, the 12-hour and 24-hour complication rates were 55.0% and 32.5%, respectively. The length of hospital stay was 2.85±1.05 and 4.22±0.92 days for the pump and standard infusion groups, respectively (P<0.001). Conclusions: Naloxone infusion using an infusion pump may be safer with regard to hemodynamic stability, resulting in shorter hospitalization periods, and fewer posttreatment complications.
H. Ghojavand,F. Vahabzadeh,F. Azizmohseni 한국생물공학회 2011 Biotechnology and Bioprocess Engineering Vol.16 No.1
A halotolerant, thermotolerant, and facultative biosurfactant producing bacterium was identified as a strain of Bacillus mojavensis based on the phenotypic data,a phylogenetic analysis, and DNA-DNA relatedness with closely-related species. This strain grew at temperatures and salinities up to 55°C and 0 ~ 10% (w/v) NaCl, respectively,and under anaerobic conditions. A batch fermentation showed that this strain secreted a lipopeptide biosurfactant that can reduce surface tension to 27 mN/m while growing on mineral medium. The emulsifying activity of the cell-free supernatant and stability of the formed emulsions were studied at various temperatures and salinities. The results showed that the ability to significantly reduce surface tension was not sufficient to form stable emulsions. The ability of this strain to grow and reduce surface tension under a wide range of salinities and temperatures gives it an advantage for many applications.
Kinetic Modeling of Cometabolic Degradation of Ethanethiol and Phenol by Ralstonia eutropha
Mahsa Sedighi,Farzaneh Vahabzadeh 한국생물공학회 2014 Biotechnology and Bioprocess Engineering Vol.19 No.2
Cometabolism, as a complex phenomenon inmicrobial world, is a special mechanism for transformationof many compounds of environmental and toxicologicalsignificance. Several models have been proposed to describethe cometabolic transformations of non-growth substratesin the absence or presence of growth substrates. In thisstudy, a model was proposed to simulate the degradationkinetics of phenol and ethanethiol (ET) by a pure culture ofRalstonia eutropha, including the effects of cell growth,endogenous cell decay, loss of transformation activity,competitive inhibition between growth and non-growthsubstrates, and self-inhibition of non-growth substrate. Themodel parameters were determined independently andwere then used for evaluating the applicability of the modelby comparing experimental data with model predictions. The model successfully predicted ET transformation andphenol utilization for a wide range of concentrations of ET(0 ~ 40 mg/L) and phenol (0 ~ 100 mg/L).
Degradation of Formaldehyde in Packed-bed Bioreactor by Kissirisimmobilized Ralstonia eutropha
Alireza Habibi,Farzaneh Vahabzadeh 한국생물공학회 2013 Biotechnology and Bioprocess Engineering Vol.18 No.3
The ability of the Ralstonia eutropha cells to utilize formaldehyde (FA) as the only source of carbon and energy was studied in the kissiris-immobilized cell bioreactor (KICB) in batch-recirculation and continuous modes of operation. In batch-recirculation experiments, the test bacterium could tolerate concentrations of FA up to 1,400 mg/L at 30oC and aeration rate equal to 0.75 vvm (rS = 7.25 mg/L/h, qS = 0.019 gFA/gcell/h). However, further increase of initial FA concentration resulted in degradation reaction of FA to stop at 1,600 mg/L. Results of continuous mode experiments showed that the biodegradation performance of the KICB was dependent on both feed flow rate and inlet FA concentration parameters. The optimum feed flow rate which corresponded to the highest biodegradation rate (rS = 240.3 mg/L/h) was observed at Q = 18 mL/min when KICB did not operate under the external mass transfer limiting regime. Substrate inhibition kinetics (Edwards and Luong equations) were used to describe the experimental specific degradation rates data. According to the Luong model, the values of the maximum specific degradation rate (qmax), half-saturation coefficient (KS), the maximum allowable FA concentration (Sm), and the shape factor (n)were 0.178 gFA/gcell/h, 250.9 mg/L, 1,600 mg/L, and 1.86,respectively.
Mozhgan Keyvani,Farzaneh Vahabzadeh,Leila Davarpanah 한국화학공학회 2014 Korean Journal of Chemical Engineering Vol.31 No.9
With use of response surface methodology (RSM), the W1/O/W2 emulsions containing ferrous sulfate asthe inner phase were optimized in terms of stability (ES) and apparent viscosity (µapp). Curvature display of the responsesaround their optimal settings was appropriately described using the quadratic polynomial regression model. The non-Newtonian behavior of the test W1/O/W2 emulsions was characterized using the power-law model and change fromnon-Newtonian to Newtonian (n1) was seen in the case of W1/O :W2 ratio equal 20 : 80 when the level of Tween-80 was 1 v%. Results of the size distribution pattern showed 60% of the particles were less than 5 µm. Rheologicalproperties of the test W1/O/W2 emulsions as the viscoelastic liquids were analyzed and the results of oscillatory ex-periments considering shear stress and frequency dependency of G' and G'' moduli were discussed in terms of the internalmicrostructure of the emulsions.
Anis Askari,Milad Taherkhani,Farzaneh Vahabzadeh 한국화학공학회 2022 Korean Journal of Chemical Engineering Vol.39 No.8
A single chamber microbial electrolysis cell (MEC) was constructed to treat olive oil mill wastewater(OOMW) biologically and produce hydrogen simultaneously. To characterize the optimal MEC condition, the MECwas fed with synthetic wastewater (SW) having a phenol concentration of 250mg l1. Therefore, the influence of differentapplied voltages and cathode materials was explored and the optimum condition for MEC was determined, whichwas when the stainless steel cathode was implemented and the external voltage of 0.6 V was supplied. Chemical oxygendemand (COD) removal of 62% and current density of 362 mA m2 were obtained for OOMW treatment, whileCOD removal of 73% and the current density of 274.4mA m2 were attained for SW treatment in this MEC at 0.6 V. Hydrogen production rate was 0.045m3 H2 m3d1 for SW and 0.053m3 H2 m3d1 for OOMW. Furthermore, the coulombicefficiency and cathodic hydrogen recovery were 23% and 81%, respectively. Finally, MEC performance in termsof electrical current generation, wastewater treatment and hydrogen production was compared to some similar reportedstudies.
Mahboobeh Bagheri,Reza Daneshvar,Azadeh Mogharei,Farzaneh Vahabzadeh 한국화학공학회 2020 Korean Journal of Chemical Engineering Vol.37 No.7
The fuel acclimation process offers flexibility in microbial fuel cell (MFC) power generation behavior. Different concentrations (50-200mg/L) of phenol were used for adapting the activated sludge (AS), obtained from a local petroleum wastewater treatment plant and Ralstonia eutropha pure culture. Anodic biomass capable of oxidizing phenol substrate, using either AS inoculum microbial consortium or R. eutropha in the MFC system, has been a reflection of growth supportive functionality of phenol and 150mg/L as initial concentration was used in the experiments. For both types of inocula. The results of phenol and COD removals obtained for closed system configuration were compared with those under open circuit condition. The current production by AS and R. eutropha was improved through phenol acclimation process. The highest power density (PD) using either AS or R. eutropha was 11 and 5.8mW/m2, respectively. In terms of using olive oil mill wastewater as the anodic substrate, the behavior of phenol-acclimated R. eutropha was better than that of the synthetic type of wastewater, and the PD value was 7.8mW/m2.