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Abstract Synthesis and employing advanced materials for emerging applications is of great challenge for the scientific community. Recombinant proteins production and purification is one of the fastest growing fields in the global economy. In this regard, it is essential to fabricate biocompatible low-cost materials with high specificity to enhance purification efficiency. This requires the regulation of mass transfer based on the protein molecular size and interactions with the matrix interface; thus, needs synthesizing novel materials with tuned porosity. In this study, we proposed rational alteration in porous structure of biopolymeric microspheres using appropriate-sized porogen to facilitate intraparticle molecular diffusion. The tailored porous nanostructures, which were generated by phase separation in the polymer blend of agarose and polyethylene glycol, were analyzed with optical and scanning electron microscopy, Fourier transform infrared spectroscopy, water diffusion, and albumin adsorption. The well-tuned beads possessed highly porous structures with dominant mesopores owing to PEG phase migration out of the network. The high speed homogenizer caused an uncommon dense morphology with interwoven two-type porosity. Optimally tuned mesoporous beads with considerably high specific surface area exhibited dramatically fast and enhanced intraparticle diffusion of both water and protein molecules. Thus, the introduced porosity modification is a promising design for enhancing mass transfer in the bio-separation process. Finally, useful insights for developing future smart hydrogel microparticles with tuned porous network for biomolecules purification are provided by the conducted experiments. Graphical abstract Unlabelled Image Highlights • A rational strategy is introduced to tune the nanostructure of agarose microspheres • Small mesopores (<20nm); thus, the highest surface area are achieved by PEG removal • High shear mixing leads to smaller beads and increased physical cross-link density • Engineered mesoporous beads show remarkable intraparticle molecular diffusion • Highly enhanced protein adsorption rate and capacity validated our proposal [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Homogeneous formation of dynamic membrane (DM) with minimum effluent turbidity using static mixer in DMBR. • Size and place of static mixer had significant effects on the formation, stability, and filtration resistance. • The shortest formation time of DM was obtained with elevation of the static mixer size. • Membrane fouling improved with changes in static mixer place. • Role of static mixer was more prominent in reduction of operational costs and energy consumption. Abstract Homogeneous formation of a dynamic membrane (DM) on macroporous materials (such as mesh filter) in a dynamic membrane bioreactor (DMBR) is very important. In this research, an economical and efficient method was introduced for homogeneous formation of DM using a static mixer. To investigate the effectiveness of the static mixer in formation and filtration of DM, in comparison with the state without a static mixer, the size of the static mixer was examined at different aeration rates. The filtration characteristics of DMBR including formation time, stability time and fouling propensity were obtained. Further, the properties of DM including the mean particle size (M ps), soluble microbial product (SMP), average thickness and porosity of DM were measured to analyze the formed DMs in the bioreactor. The results indicated that the static mixer size (r p = −0.892) has the maximum effect on the formation time. With the crossflow velocity control, the static mixer contributed to homogeneous formation of cake layer and increased share of large particles on the mesh filter surface at the very beginning, such that the minimum formation time was achieved. Moreover, to achieve suitable conditions for the site of static mixer in the bioreactor, the effects of the place of the static mixer were examined in the best DM formation state (formation time < 5 min). It had a great impact on the stability time (r p = −0.941) and fouling propensity (r p = 0.926). Based on the obtained results, application of static mixer can contribute to saving energy and promoting the DMBR technology in wastewater treatment through shortening DM formation time and decreasing membrane fouling. [ABSTRACT FROM AUTHOR]

Employing magnetic beads for immobilized metal affinity chromatography application was studied with the approach of magnetic effects investigation. Hence, fabricated magnetic nanoparticles-carrying beads were functionalized with Ni(II)-iminodiacetic acid (IDA). BET-BJH results showed that nanoparticles affected pore sizes lower than 10 nm. Therefore, the pore blockage by protein molecules is considered as an outcome of the new pore diameter in magnetic beads. In accordance, bovine serum albumin (BSA) adsorption isotherms revealed a significant difference between magnetic and nonmagnetic beaded matrices. For nonmagnetic beads, adsorption isotherm followed Langmuir model. However, one step increase in adsorption isotherm for initial BSA concentration from 0.5 mg/ml to 0.8 mg/ml was observed on magnetic beads due to pore blockage by proteins. BSA Adsorption kinetics on beads was found to follow the assumptions of an intraparticle diffusion-controlled pseudo-second order mechanism, with higher adsorption rate constants at lower adsorbate concentrations. Furthermore, though the same IDA density on both non/magnetic beads, presence of magnetic nanoparticles reduced the required equilibrium time (up to 60 min), the saturation path of BSA adsorption breakthrough curves, dynamic binding capacity and the number of theoretical plates. It is concluded that magnetic characteristic of composite agarose adsorbent carrying Fe 3 O 4 nanoparticles affects protein’s conformation. Thus, BSA travel toward ligand is enhanced and sped up. [ABSTRACT FROM AUTHOR]

The aim of this study is the synthesis of a magnetic nanocomposite membrane to reduce fouling in a magnetic membrane bioreactor. To this end, Fe 3 O 4 nanoparticles with an approximate size of 60–70 nm were settled into the polysulfone ultrafiltration membrane matrix through blending of Fe 3 O 4 nanoparticles with the dope solution. Nanocomposite membranes containing 0–0.11 wt% Fe 3 O 4 nanoparticles submerged in the magnetic bioreactor system in which the MLSS was considered between 8000–16,000 g/L and the magnetic field intensity was 40–160 mT. The results showed that an increase in the concentration of nanoparticles reduced the filtration resistance as much as 48% and developed the COD removal as much as 24% and increased the flux as large as 30%. The presence of a magnetic field around the bioreactor reduced the total filtration resistance as much as 68% and increased the COD removal as much as 34% due to the production of some changes in the membrane morphology and the sludge properties. Comparing the performance of the synthesized nanocomposite membranes with a MICRODYN-NADIR commercial membrane sample showed that magnetic nanocomposite membranes possess 30% higher flux, 27% lower filtration resistance, 41% higher COD removal compared to a commercial membrane. [ABSTRACT FROM AUTHOR]

In this study, a submerged membrane was installed in a bioreactor to treat N-riched wastewater and obtain high biomass productivity. Chlorella vulgaris was cultivated under mixotrophic, heterotrophic, and photoautotrophic conditions in different kinds of nitrogen sources (nitrate and ammonium) to compare the microalgae growth and nutrient removal in a membrane bioreactor. Further, the respirometric and photosynthetic activities of microalgae were investigated to evaluate the viability of microalgae in different conditions. The highest biomass productivity was obtained under mixotrophic cultivation in ammonium source (0.230 ± 0.009 gr/L d). Moreover, with this type of cultivation and nitrogen source, specific oxygen uptake rate (SOUR) was higher than oxygen product rate (SOPR). However, SOPR improved in mixotrophic cultivation using nitrate source. In both nitrogen source types, the photosynthetic activity of mixotrophic microalgae was reduced at high cell density. Compared favorably with other cultivation types, mixotrophic microalgae could achieve high N and P removal rates (about 23.64–28.84 and 4.38–5.08 mg/L d, respectively). In all cultivation types (except photoautotrophic condition with nitrate source), N and P removal amounts were assimilated to biomass. Based on the obtained results, membrane bioreactor containing mixotrophic microalgae would be the most useful system for application in N-riched wastewater treatment systems. [ABSTRACT FROM AUTHOR]

In this study the effects of Al2O3 nanoparticle concentration were investigated on the membrane structure/performance; the boundary of variations was detected, introduced as Nanoparticle Concentration Threshold (NCTh), and was used for forecasting the field of membrane application. For this purpose, Al2O3 nanoparticles with a size of 70 nm and a concentration between 0 and 0.52 Wt.% were added to the membrane matrix. Loading threshold of Al2O3 nanoparticles was evaluated and the properties of the nanocomposite membrane were compared up and sub the loading threshold. Rheometric analysis, contact angle measurement, SEM images, and filtration experiments showed that concentration threshold of Al2O3 nanoparticles was 0.39 Wt.%. Based on their properties, the antifouling performance of those membranes possessing Al2O3 concentration below the threshold was evaluated in a membrane bioreactor (MBR). [ABSTRACT FROM AUTHOR]

The aim of this study is to investigate the effect of the presence and impregnation of iron oxide nanoparticles with the polysulfone membrane matrix. The nanoparticles were synthesized via co-precipitation method and were added to the membrane structure through blending with the polymeric matrix (Blended Nanocomposite Membranes (BNM)), deposition by photopolymerization (PhotoPolymerized Nanocomposite Membranes (PPNM)) and deposition by interfacial polymerization (Interfacially Polymerized Nanocomposite Membranes (IPNM)). FTIR analysis proved the presence of nanoparticles in all of the three types of membranes. According to AFM images, nanoparticles enhance the membrane roughness. On the account of SEM images obtained from the membrane surface, nanocomposite membranes have a more uniform surface compared to neat polymeric membranes. In addition, the cross-sectional SEM images of the membrane revealed that the blending method provides the opportunity of controlling the membrane morphology by means of nanoparticles. Contact angle analysis confirmed the development of nanocomposite membrane hydrophilicity versus neat polymeric membranes. The filtration experiments including permeation flux, dye rejection, and molecular weight cut off were done to compare all of the nanocomposite membranes. The results indicated that the blending method can improve the membrane structural properties and the deposition method can improve their separation yield. [ABSTRACT FROM AUTHOR]

Highlights: [•] pH sensitive polyacrylic acid layer was deposited on polysulfone membrane by photopolymerization. [•] The deposited polyacrylic acid improved amoxicillin separation of nanofiltration membranes. [•] Surface charge is more effective than membranes pore size in amoxicillin separation efficiency. [•] The pH sensitivity of membranes makes charge repulsion as dominant separation mechanism. [•] Effect of pH on separation membrane efficiency was assessed by FTIR spectra. [ABSTRACT FROM AUTHOR]

Highlights: [•] To develop formation process of self-forming dynamic membrane on mesh filter. [•] To optimize imposed flux and aeration rate for self-forming dynamic membrane. [•] To evaluate efficiency of dynamic membrane bioreactor in removal of COD and TDS. [•] To investigate the preferable cleaning method for recovery of fouled mesh filter. [•] To characterize dominant chemical matter in dynamic membrane using FTIR analysis. [ABSTRACT FROM AUTHOR]

Highlights: [•] Presence of cations in MBR removes colloids, soluble biopolymers and induces bioflocculability of activated sludge. [•] Introduction of different multivalent metallic cations is a way of fouling mitigation in MBRs. [•] Pore blocking and cake layer permeability of membrane hydraulic resistance decreased with charge density. [•] Membrane fouling was correlated to biopolymers concentration and mean flocs size of activated sludge. [Copyright &y& Elsevier]

Abstract: In this study membrane fouling was studied in a novel airlift oxidation ditch membrane bioreactor (AOXMBR) working under various high organic loading rates (OLRs). The results confirmed the high performance of AOXMBR in terms of Chemical Oxygen Demand (COD) removal, even at very high OLRs. The role of the membrane barrier appeared to be significant when the COD in the supernatant was high under such conditions. In addition, the study confirmed the performance of the AOXMBR was better in comparison with the conventional activated sludge as such colloid matters cannot be retained via a simple secondary settling step. Also, on-line viability measurement of the activated sludge illustrated that the fouling increased with a decrease in the viability of the activated sludge. The results showed that the qualitative change of the activated sludge affected the fouling phenomenon. The membrane fouling dynamics analysis pointed out the relationship between cause of the membrane fouling and MBR operating conditions. Adsorption in pores appeared to be the dominant cause when any biofilm or deposit was present on the membrane surface. On the other hand at high OLR in the absence of any deficiency (oxygen deficiency, large pH variations etc.) for the microbial population the biofilm played the dominant role consequent, whereas with drastic decreases of OLRs -due to significant cell lysis – external and reversible deposits appeared as the dominant cause of membrane fouling. [Copyright &y& Elsevier]

Abstract: This work investigates filtration performance of mesh filter bioreactor for synthetic municipal wastewater treatment. Critical flux is measured by flux stepping method and the effect of aeration rate on the critical flux is investigated. The long term monitoring of trans-filter pressure evolution at sub and super-critical fluxes is performed. The analysis of resistance is achieved by determination of resistances and microscopic observation of bio-cake. Cake resistance values vary from 78% to 92% of total filtration resistance for sub and super-critical fluxes. The effect of variations of specific aeration demands (SADm: 0.5–6m3/m2 h) on suspended solid of effluent, turbidity of filtrate, filtration resistance, and zeta potential of biomass is evaluated. The results show that filtrate quality is decreased when the aeration rate increases. It is attributed to stable formation of dynamic membrane. A rather clear filtrate, less than 18 NTU of turbidity, is obtained for SADm 0.5m3/m2 h. The results also show that the total filtration resistance of the sub-critical flux significantly decreases with increasing aeration intensity until SADm 2m3/m2 h and thereafter slightly decreases. It is also shown that the variations of zeta potential of biomass with aeration rate highly correspond to the alterations of filtration resistance. [Copyright &y& Elsevier]

Abstract: For the first time, growing cells of Gordonia alkanivorans RIPI90A were used for biodesulfurization (BDS) of diesel. This process was carried out in an internal airlift bioreactor. BDS parameters (oil/water phase ratio and initial sulfur concentration) were optimized in flasks using response surface methodology. Predicted results were found to be in good agreement with experimental results. Initial sulfur concentration had a remarkable effect on BDS process. Maximum removal of sulfur (21mg/l) can be achieved at oil/water phase ratio of 25% (v/v) and initial sulfur concentration of 28mg/l. Moreover, effect of superficial gas velocity (U g) and working volume (v) on volumetric gas liquid mass transfer coefficient was studied in an airlift bioreactor for BDS of diesel. The best results were achieved at U g and v of 2.5l/min and 6.6l, respectively. Subsequently, BDS of diesel was investigated in an airlift bioreactor under optimized conditions. Sulfur reduction after 30h was 14mg/l. [Copyright &y& Elsevier]

Abstract: In this study, experiments and computational fluid dynamics were used to evaluate the fouling of membrane surfaces. Based on the resistance-in-series model, the total filtration resistance (R t ) was divided into cake resistance (R c ), adsorption resistance (R a ), internal-plugging (pore-blockage) resistance (R pb ) and intrinsic-membrane resistance (R m ). The values of each resistance and their relative percentages as a function of the operating parameters were experimentally determined. The effect of inlet air-flow rate and the baffle angle on the resistances were also investigated. It was then shown that the permeate flux and resistances could be related to the wall shear stresses of air and liquid flows at the membrane surface. Average shear stress was found to increase by increasing the air-flow rate. The change in baffle angle from 90° to 85° increased the shear stress of air on the membrane surface. At low air-flow rates there was a lower meandering of air as well as the area of the membrane, which is not subject to high-shear increases. The shear stresses of air and liquid on the membrane surface were determined by computational fluid dynamics and correlations were proposed for estimating each resistance of the membrane from these shear stresses. [Copyright &y& Elsevier]

Abstract: Gas hold-up (ɛ g), sauter mean bubble diameter (d 32) and oxygen transfer coefficient (k L a) were evaluated at four different alkane concentrations (0.05, 0.1, 0.3 and 0.5vol.%) in water over the range of superficial gas velocity (u g) of (1.18–23.52)×10−3 m/s at 25°C in a laboratory-scale bubble column bioreactor. Immiscible hydrocarbons (n-decane, n-tridecane and n-hexadecane) were utilized in the experiments as impurity. A type of anionic surfactant was also employed in order to investigate the effect of addition of surfactant to organic-aqueous systems on sauter mean bubble diameter, gas hold-up and oxygen transfer coefficient. Influence of addition of alkanes on oxygen transfer coefficient and gas hold-up, was shown to be dependent on the superficial gas velocity. At superficial gas velocity below 0.5×10−3 m/s, addition of alkane in air–water medium has low influence on oxygen transfer coefficient and also gas hold-up, whereas; at higher gas velocities slight addition of alkane increases oxygen transfer coefficient and also gas hold-up. Increase in concentration of alkane resulted in increase in oxygen transfer coefficient and gas hold-up and roughly decrease in sauter mean bubble diameter, which was attributed to an increase in the coalescence-inhibiting tendency in the presence of surface contaminant molecules. Bubbles tend to become smaller with decreasing surface tension of hydrocarbon, thus, oxygen transfer coefficient increases due to increasing of specific gas–liquid interfacial area (a). Empirical correlations were proposed for evaluating gas hold-up as a function of sauter mean bubble diameter, superficial gas velocity and interfacial surface tension as well as evaluating Sherwood number as a function of Schmidt, Reynolds and Bond numbers. [Copyright &y& Elsevier]

Abstract: Gas hold-up (εg) and volumetric gas–liquid oxygen transfer coefficient (kLa) in a draft-tube airlift bioreactor (24×10-3m3 in volume) were studied using pure kerosene and diesel and their water-in-oil microemulsions, as the model solutions for petroleum biodesulfurization. For comparison, experiments were also done with distilled water. The εg and the kLa values for kerosene and diesel systems were in most cases significantly higher than the water system. Increase in water-to-oil phase volume ratio (φ) of the microemulsion systems resulted in decrease in the values of εg, which was attributed to a decrease in the coalescence-inhibiting tendency of the petroleum liquids. Increase in the viscosity () of the microemulsion systems to around 32×10-6m2/s resulted in the occurrence of the churn turbulent regime with an associated decrease in the value of εg, which could not be solely accounted for by the increase in φ. Furthermore, the kLa values decreased with increase in the viscosity of the petroleum-based liquids. However, when churn turbulent conditions prevailed, increase in viscosity alone could not account for the decrease observed in the kLa values. Empirical correlations were developed that related εg and kLa to φ and ν, respectively, under the bubbly flow regime inside the bioreactor. [Copyright &y& Elsevier]

Abstract: Treatment of pharmaceutical wastewater is a real challenge for wastewater engineers. In this study, a pilot-scale system including an external loop airlift membrane bioreactor (ELAMBR) was applied for treatment of a synthetic pharmaceutical wastewater. The performance of this system was evaluated in removal of acetaminophen as the main pollutant of a pharmaceutical wastewater. A conventional activated sludge (CAS process) laboratory system was used in parallel with this system to compare both systems in regard to their ability for acetaminophen removal. The performance of the ELAMBR system was monitored for approximately one month to investigate the long-term operational stability of the system and possible effects of solids retention time on the efficiency of removal of acetaminophen. The removal efficiency was significantly higher in the ELAMBR system than the CAS process. 100% of the acetaminophen was removed after 2days in this system. The results also showed that initial concentration of acetaminophen, chemical oxygen demand (COD) and mixed liquid suspended solids (MLSS) are the most effective parameters in removal of a pollutant such as acetaminophen. This study demonstrates the usefulness of ELAMBR system for pharmaceutical wastewater treatment with the advantages such as: (i) simple operation and maintenance, (ii) efficient removal of pharmaceutical pollutant and COD and (iii) low-energy consumption. [Copyright &y& Elsevier]

In this research, to benefit from the hydrophilic properties of zirconia nanoparticles as well as the role of iron oxide nanoparticles in improving porosity of polymer membranes simultaneously, Fe 3 O 4 @ZrO 2 /PAN nanocomposite membrane was synthesized and its performance was examined in reducing biological fouling of the membrane. FESEM analysis confirmed a size distribution of 35–55 nm, and TEM analysis confirmed a core-shell structure for Fe 3 O 4 @ZrO 2 nanoparticles. FTIR analysis identified the functional groups in the Fe 3 O 4 @ZrO 2 nanoparticles and confirmed their presence in the matrix of 1 Fe 3 O 4 @ZrO 2 /PAN NCM membrane. Contact angle analysis confirmed the role of zirconia nanoparticles in enhancing the membrane hydrophilicity by 51%, and porosimetry analysis confirmed the role of iron oxide nanoparticles in improving porosity of nanocomposite membranes by 47%. Usage of 1 wt% of Fe 3 O 4 @ZrO 2 nanoparticles in the PAN membrane matrix brought about 40% increase in water flux and 37% growth in dye rejection for 1Fe 3 O 4 @ZrO 2 /PAN NCM membrane. Investigation of the role of Fe 3 O 4 @ZrO 2 nanoparticles in the filtration of biological macromolecules indicated that 1 Fe 3 O 4 @ZrO 2 /PAN NCM membrane has 60%, 51%, and 56% less resistance to filtration of humic acid, sodium alginate, and BSA, respectively, when compared with raw membranes. [ABSTRACT FROM AUTHOR]

The aim of this study was to investigate the applicability of the adsorption process for the removal of organophosphorus pesticide malathion 57% from water by using multi-walled carbon nanotubes (MWCNTs). The impact of various experimental conditions such as pH, quantity of adsorbent, concentration of pesticides, contact time and temperature was studied and optimized for the maximum removal of malathion. Unlike conventional optimization, a limited number of experiments (26 steps) were performed in a cost-effective manner for different independent variables such as MWCNTs concentration (0.1–0.5 g/L), the malathion (57%) concentration (6 mg/L and 10 mg/L), contact time (2–30 min) and pH (neutral range). Based on the experimental data obtained in a lab-scale batch study, a three-factor response surface modeling (RSM) approach was implemented in order to optimize the conditions for maximum removal of malathion, and compare experimental results with standardized malathion samples. The optimized conditions to achieve the maximum removal of malathion (100%) were determined to be a malathion concentration of 6 mg/L, an initial MWCNTs concentration of 0.5 g/L, and a contact time of 30 min. Findings of this study clearly indicated that 100% of the malathion could be cost-effectively removed by MWCNTs in conditions predicted by the proposed optimization methodology. [ABSTRACT FROM AUTHOR]

Abstract: The effects of sludge viability on process performance and membrane fouling in a membrane bioreactor were investigated. A laboratory-scale submerged membrane bioreactor (SMBR) containing a flat-sheet microfiltration membrane was used at various percentages of living cellular flocs and dead cells. The effect of live to dead cells ratio on the extracellular polymeric substances (EPS) concentration was also studied. The proportion of dead cells affected the type of EPS in the mixed liquor as well as hydrophobicity of activated sludge. Tightly bound EPS (TB-EPS) mitigated membrane fouling, whereas loosely bound EPS (LB-EPS) caused severe membrane fouling. The results show that the content of TB-EPS and LB-EPS increases with dead cells portion. Furthermore, the ratio of TB-EPS to LB-EPS was presented as an important parameter in MBR performance. It was showed that this ratio is a good representative of flocculability of activated sludge and fouling intensity. Compared to the live cells, the dead cells had lower hydrophobicity and induced membrane fouling so that membrane permeability of the viable activated sludge was twice of the dead cell culture. The potential of zone settling velocity (ZSV) to be considered as a key parameter in MBR operation was also reported. [Copyright &y& Elsevier]

Abstract: The rising demand for high quality water heightens the need to soften hard and very hard water. In this study, flat sheet polysulfone ultrafiltration membranes were prepared by phase inversion and modified by UV-induced polymerization of acrylic acid in order to prepare nanofiltration membranes for water desalination. Polyethylene glycol of different molecular weights mainly in the range of 1500–4000Da were used in the casting solution and acrylic acid was polymerized on the membrane surface. In this way, a manipulated membrane was prepared with higher pore size and higher surface charge density for improved water softening. The results show that by increasing irradiation time and monomer concentration in the photografting process, pure water flux declines and salt rejection increases. For a membrane photografted for 180min with acrylic acid solution (6wt.%) and PEG-4000 as additive, the rejection of Na2SO4, MgSO4, NaCl and CaCl2 follows a decreasing in order of 100%, 77.9%, 49.9% and 35.9% respectively. The RMS roughness of the prepared membrane is 1.65nm, which is well in the nanofiltration roughness range. Featuring a large pore size and high surface charge density, the developed nanofiltration membranes show a promising capability for water desalination. [Copyright &y& Elsevier]

Abstract: Mathematical modeling of fatty acids (FAs) extraction from Trout powder by supercritical carbon dioxide was performed in the present work. Trout powder with its low cost contains high amount of essential FAs and it is commonly available as a proper source of FAs. The effect of process parameters, such as pressure (25, 28, 31, 34 and 37MPa) and temperature (310, 318 and 326K) of extraction and void fraction of the bed (0.25, 0.35 and 0.45, v/v) on the yield of FAs extraction was examined in a series of experiments conducted in a laboratory scale apparatus. The results indicated a significant increase of extraction yield with an increase of pressure from 25 to 34MPa, but working at the higher pressure (37MPa) caused reduction of the extract. Increasing the temperature higher than 318K revealed significant reduction of the FAs yield and increasing the bed void fraction from 0.25 to 0.45 showed enhancement of the extraction. The mathematical model was developed considering diffusion-controlled regime in the particle and film mass transfer resistance around the particle with axial dispersion of the bulk phase at dynamic conditions. Henry law was used to describe the equilibrium state of solid and fluid phases. The proposed mass balance equations were numerically solved using implicit finite difference method and the model parameters were correlated using the experimental results of the outlet FAs concentration in the oil extracted at dynamic conditions. Well-known Nelder–Mead method was applied to estimate the four parameters of the model, namely, mass transfer coefficient (k f), axial dispersion coefficient (D ax) in the bulk phase, effective diffusivity (D eff) into the pores and Henry coefficient (H). In the range of studied conditions, the higher extraction efficiency with higher pressure resulted lower correlated H, although the temperature increasing which showed a retrograde phenomena in the FAs yield, revealed H passing though a minimum. [Copyright &y& Elsevier]

Abstract: Determinations of pertinent hydrodynamic and mass transfer parameters were carried out inside draft tube internal loop airlift bioreactor (DTAB) containing water in diesel (W/D) microemulsions with water to diesel volume ratio (φ) in the range 2.5–40%. For comparative purposes, data for diesel and water was also obtained. Increase in φ of the microemulsion systems up to 40% or increase in the amount of surfactant used to make the microemulsions resulted in a decrease in the values of ɛ g and k L a, which was attributed to the increase in the viscosity of the microemulsions. This viscosity was found to be a more suitable correlating parameter than φ. Increase in the value of φ of the W/D microemulsion resulted in a decrease in the values of liquid velocity for u gr up to 0.032m/s. At higher gas velocities, similar values were obtained for all the microemulsions. On the other hand, increase in φ of the W/D microemulsion resulted in increase in both the circulation time and mixing time values obtained inside the DTAB, although the difference was more pronounced at lower values of u gr. Suitable empirical correlations relating ɛ g , k L a, , circulation time and mixing time to riser superficial gas velocity (u gr) and kinematic viscosity were presented. The downcomer holdup data for diesel and W/D microemulsions was related to the riser holdup data using a single correlation. [Copyright &y& Elsevier]

Highlights: [•] The impact of OLR on viability and activity of activated sludge sometimes is different. [•] SMP release in the bioreactor depends on the viability of activated sludge. [•] Novel method based on capacitance was introduced for viability of activated sludge. [•] Determination of activated sludge quality is important for efficient operation of MBR. [ABSTRACT FROM AUTHOR]

Abstract: In this work, biosurfactant production by Bacillus subtilis, Pseudomonas aeruginosa, and Bacillus cereus has been compared. These microorganisms were isolated from agricultural and oil polluted area of Iran. Maximum biosurfactant production reached to about 1.6g/l and liquid surface tension decreased from 72 to 25mN/m using B. subtilis. All screened bacteria exhibited a good ability to emulsify the crude oil. Biosurfactant of B. subtilis attained an emulsion index of 75% for crude oil which was significantly greater than other strains. Stability studies were carried out under the extreme environmental conditions as find normally in the oil reservoir such as high temperature, pH and salinity. Results showed an excellent resistance of all produced biosurfactants to retain their surface-active properties at extreme conditions. It was found that the biosurfactants show a good stability around pH of 4 but at lower pH, they will harmfully be affected. Lesser precipitation has been observed at low pH for biosurfactant produced by B. subtilis. It has also been observed that biosurfactants from three isolated bacteria were able to support the condition up to 25g/l salinity. B. cereus biosurfactant was even stable at the higher salinity. Regarding temperature, all produced biosurfactants demonstrated a good stability in the temperature up to 120°C. Oil displacement experiments in micromodel with kerosene showed around 25% recovery of residual oil after water flooding when the biosurfactant of B. subtilis was added. These results suggest that biosurfactants of these indigenous isolated strains are appropriate candidates for enhanced oil recovery with a preference to biosurfactant of B. subtilis. [ABSTRACT FROM AUTHOR]

Abstract: In an industrial fermentation of Bacillus thuringiensis, it is important to verify the intactness of bacterial plasmid content in all steps of culture. Changes in some plasmid resident properties of this bacterium could be considered as the simple potential signs of changes in the plasmid content. For studying this matter, two Cry+ (mother strain) and Cry− phenotype strains of B. thuringiensis H14 were compared. They showed different properties in many studied levels. Facing the presence of seven plasmids in the Cry+ strain only one small plasmid was observed in the Cry− strain. Despite the ability of mother strain to form aggregates (Agr+), no aggregation was observed in the Cry− phenotype (Agr−). The colony morphology of Cry+ strain was R shape while Cry− formed S shape colonies. Cry− strain grew faster than Cry+ strain, but both of them were capable to do sporulation. The protein profile using SDS-PAGE showed the presence of a 130, 65, and 25kDa Cry protein in the Cry+ strain whereas these proteins were absent in the Cry− strain. The Cry− was not toxic against Aedes aegypti and Culex pipiens larvae. [Copyright &y& Elsevier]