Performance evaluation of batch and unsteady state fed‐batch reactor operations for the production of a marine microbial surfactant

BACKGROUND: Biosurfactants are microbially derived surface‐active and amphipathic molecules produced by various microorganisms. These versatile biomolecules can find potential applications in food, cosmetics, petroleum recovery and biopharmaceutical industries. However, their commercial use is impeded by low yields and productivities in fermentation processes. Thus, an attempt was made to enhance product yield and process productivity by designing a fed‐batch mode reactor strategy. RESULTS: Biosurfactant (BS) production by a marine bacterium was performed in batch and fed‐batch modes of reactor operation in a 3.7 L fermenter. BS concentration of 4.61 ± 0.07 g L^?1 was achieved in batch mode after 22 h with minimum power input of 33.87 × 10³ W, resulting in maximum mixing efficiency. The volumetric oxygen flow rate (K_La) of the marine culture was about 0.08 s^?1. BS production was growth‐associated, as evident from fitting growth kinetics data into the Luedeking‐Piret model. An unsteady state fed batch (USFB) strategy was employed to enhance BS production. Glucose feeding was done at different flow rates ranging from 3.7 mL min^?1 (USFB‐I) to 10 mL min^?1 (USFB‐II). USFB‐I strategy resulted in a maximum biosurfactant yield of 6.2 g l^?1 with an increment of 35% of batch data. The kinetic parameters of USFB‐I were better than those from batch and USFB‐II. CONCLUSION: Comparative performance evaluation of batch and semi‐continuous reactor operations was accomplished. USFB‐I operation improved biosurfactant production by about 35% over batch mode. USFB‐I strategy was more kinetically favorable than batch and USFB‐II. © 2012 Society of Chemical Industry     

Study on the enzymatic hydrolysis of racemic methyl ibuprofen ester

The hydrolysis of racemic methyl ibuprofen ester in the presence of lipase from Candida rugosa was investigated in shake flasks. Experiments were performed to study the effect of temperature, pH and shaking speed on the reaction rate. Different hydrophobic co‐solvents were screened for the highest reaction rate and the presence of enzyme inhibition by substrate and products was examined. A kinetic expression was then proposed to describe the reaction. Kinetic parameters were determined for the optimum operating conditions and the proposed model was verified with the experimental results. Next, this reaction was scaled up to a fed batch stirred tank reactor. Batch reactor and fed batch reactor configurations were compared for better conversions. The effects of aqueous phase hold‐up, substrate concentration and feed flow rate on the conversion of the reaction were also studied. Higher conversions were obtained in a fed batch reactor when compared with the batch reactor. In the fed batch reactor, increased conversions were observed with lower feed flowrates and high aqueous phase hold‐up. © 2001 Society of Chemical Industry     

Fed‐batch fermentation of olive mill wastewaters for lipase production

In the Mediterranean basin countries, huge amounts of olive mill wastewaters (OMW) are produced by the olive oil industry. It constitutes a serious environmental problem, nevertheless its composition turns OMW into a potential growth medium to lipolytic microorganisms. The aim of this work was to study lipase production as well as OMW degradation in fed‐batch cultures of Candida cylindracea CBS 7869, Candida rugosa CBS 2275 and Yarrowia lipolytica W29 (ATCC 20460). Besides the improvement of lipase production, the fed‐batch approach enhanced the effluent degradation, since it led to good COD and lipids reduction, both higher than 50%. C. rugosa achieved the highest value of lipase productivity (130 U L^?1 h^?1), in parallel with highest lipids reduction (77%). This study demonstrates that OMW are becoming a competitive and valuable growth medium in fermentation processes with lipolytic microorganisms. The fed‐batch strategy used proved to be an efficient approach to enhance lipase production from OMW and to reduce significantly the final organic load of the medium. Copyright © 2012 Society of Chemical Industry     

Continuous perfusion culture of encapsulated hybridoma cells

BACKGROUND: The production of Monoclonal antibodies (mAbs) is often performed in batch or fed‐batch operations where low cell densities and low volumetric productivities are achieved. The main bottleneck of both processes is the short operating time with productive cells at maximum cell concentration. RESULTS: The process studied in this work is based on a fluidized‐bed bioreactor culture of encapsulated KB26.5 cells in a liquid core of calcium alginate microcapsules as a culture strategy to produce IgG₃. First, DMEM medium was modified in order to protect the microcapsules from degradation, and later, the optimal operating conditions were set. Under these conditions encapsulated KB26.5 cells reached cell densities of 1.05 × 10⁸cells mL^?1 or 9.8 × 10⁶ cells mL^?1 (referred to the inner capsule volume or total bioreactor volume, respectively), and a mAb volumetric productivity of 2.75 µg mL^?1 h^?1. CONCLUSIONS: The productivity of encapsulated KB26.5 cells in perfusion culture was enhanced significantly in comparison with batch and fed‐batch processes. Continuous operation of the perfusion culture for periods longer than 35 days, represented a volumetric productivity about five‐fold higher than conventional operations. However, the fluidized‐bed also showed limitations such as low cell viability at high cell densities due to the mass transfer limitations of large molecules inside the microcapsules. Copyright © 2011 Society of Chemical Industry     

Simultaneous saccharification and fermentation of sludge‐containing cassava mash for batch and repeated batch production of bioethanol by Saccharomyces cerevisiae CHFY0321

BACKGROUND: The aim of this study was to examine the repeated batch production of bioethanol from sludge‐containing cassava mash as starchy substrate by flocculating yeast to improve volumetric bioethanol productivity and to simplify the process of a pre‐culture system. RESULTS: For the repeated batch production of bioethanol using cassava mash, the optimal recycling volume ratio was found to be 5%. The repeated batch fermentation was completed within 36 h, while the batch fermentation was completed after 42 h. Volumetric productivity, final ethanol concentration, and ethanol yield were attained to 2.15 g L^?1 h^?1, 83.64 g L^?1, and 85.15%, respectively. Although cell accumulation in the repeated batch process is difficult due to the cassava mash, the repeated batch process using Saccharomyces cerevisiae CHFY0321 could exhibited 10‐fold higher initial viable cell number (1.7 × 10⁷ CFU mL^?1) than that of the batch process. CONCLUSION: The liquefied cassava powder was directly used for the repeated batch process without removal of sludge. Repeated batch bioethanol production by simultaneous saccharification and fermentation using self‐flocculating yeast could reduce process costs and accelerate commercial applications. This result was probably due in part to the effect of the initial viable cell density. Copyright © 2008 Society of Chemical Industry     

Production of Yarrowia lipolytica lipase LIP2 in Pichia pastoris using the nitrogen source‐regulated FLD1 promoter

BACKGROUND: Yarrowia lipolytica lipase LIP2 (YlLIP2) is an important industrial enzyme that has many potential applications. Although it has been successfully expressed in Pichia pastoris under the control of the AOX1 promoter (pAOX1), there have been many efforts to develop new alternative promoters to pAOX1 in order to avoid using methanol in the fermentation. Investigation of YlLIP2 production in P. pastoris using the formaldehyde dehydrogenase 1 promoter (pFLD1) is especially attractive, since little is known about its application in methanol‐free culture strategies. RESULTS: Three fed‐batch cultivations were performed to investigate the production of YlLIP2 in a pFLD1‐based system. When methanol was used as the fed‐batch feeding substrate, the maximum YlLIP2 activity obtained in a 10‐L bioreactor was 30 000 U mL^?1 after 143 h of culture, whereas the maximum YlLIP2 activity was further increased to 35 000 U mL^?1 by adopting a co‐induction strategy with methanol and methylamine as a mixed fed‐batch substrate. Furthermore, the maximum YlLIP2 activity reached 13 000 U mL^?1 after 80 h of cultivation in a methanol‐free culture. CONCLUSION: The expression levels of YlLIP2 in the pFLD1‐based system were comparable with those in a pAOX1‐based system. The results suggest that pFLD1 is an attractive alternative to pAOX1, and may make it feasible to induce high yields of protein expression. Copyright © 2011 Society of Chemical Industry     

Effect of sucrose on nisin production in batch and fed‐batch culture by Lactococcus lactis

The effects of sucrose on cell growth and nisin production by Lactococcus lactis were investigated in batch and pH feed‐back controlled fed‐batch cultures. In batch cultures, nisin titer reached its maximum, 2658 IU cm^?3, at the initial sucrose concentration of 30 g dm^?3. With sucrose concentrations higher than 30 g dm^?3, nisin production decreased while the biomass was not influenced significantly. By using the pH feed‐back controlled method, residual sucrose concentration could be controlled well in fed‐batch cultures and three conditions (sucrose maintained at 2, 16, 20 g dm^?3, respectively) were evaluated. Maintaining a low sucrose concentration at 2 g dm^?3 during feeding favored nisin biosynthesis, and the maximum nisin titer obtained was 4961 IU cm^?3 compared with 3370 IU cm^?3 (16 g sucrose dm^?3)and 3498 IU cm^?3 (20 g sucrose dm^?3), respectively. Copyright © 2005 Society of Chemical Industry     

High power generation with simultaneous COD removal using a circulating column microbial fuel cell

BACKGROUND: A circulating column microbial fuel cell (MFC) with Cu anode and Au? Cu air cathode was used for power generation and chemical oxygen demand (COD) removal from synthetic wastewater. The column was operated in repeated‐fed batch mode using acclimated anaerobic sludge. The contents of the column MFC were circulated while the feed wastewater was fed to the reactor in fed‐batch mode. Effects of feed COD concentration and COD loading rate on voltage difference, power density and percentage COD removal were investigated. RESULTS: The highest voltage difference (650 mV), power density (40 W m^?2) were obtained with a feed COD of 6400 mg L^?1, yielding 45% COD removal with a COD loading rate of nearly 90 mg h^?1. Low COD loadings (<90 mg h^?1) caused substrate limitations, and high loadings (>90 mg h^?1) resulted in inhibition of COD removal and power generation. The highest percentage COD removal (50%) was obtained with feed COD content of 10.35 g L^?1 or a COD loading rate of 145 mg h^?1. CONCLUSION: The power densities obtained with the circulating column MFC were considerably higher than those reported in the literature due to elimination of mass transfer limitations by the high circulation rates, proximity of electrodes and small anode surface area used in this study. Further improvements may be possible with optimization of the operating parameters. Copyright © 2009 Society of Chemical Industry     

Sorption of copper by a highly mineralized peat in batch and packed‐bed systems

BACKGROUND: The performance of peat for copper sorption was investigated in batch and fixed‐bed experiments. The effect of pH was evaluated in batch experiments and the experimental data were fitted to an equilibrium model including pH dependence. Hydrodynamic axial dispersion was estimated by tracing experiments using LiCl as a tracer. Six fixed‐bed experiments were carried out at copper concentrations between 1 and 60 mg dm^?3 and the adsorption isotherm in dynamic mode was obtained. A mass transport model including convection–dispersion and sorption processes was applied for breakthrough curve modelling. RESULTS: Maximum uptake capacities in batch mode were 22.0, 36.4, and 43.7 mg g^?1 for pH values of 4.0, 5.0, and 6.0, respectively. Uptake capacities in continuous flow systems varied from 36.5 to 43.4 mg g^?1 for copper concentrations between 1 and 60 mg dm^?3. Dynamic and batch isotherms showed different shapes but a similar maximum uptake capacity. Sorbent regeneration was successfully performed with HCl. A potential relationship between dispersion coefficient and velocity was obtained with dispersion coefficients between 5.00 × 10^?8 and 2.95 × 10^?6 m² s^?1 for water velocities ranging between 0.56 × 10^?4 and 5.03 × 10^?4 m s^?1. The mass transport model predicted both the breakpoints and the shape of the breakthrough curves. CONCLUSIONS: High retention capacities indicate that peat can be used as an effective sorbent for the treatment of wastewater containing copper ions. Copyright © 2009 Society of Chemical Industry     

Enhancement of the interfacial transfer of iodine by chemical reaction

Enhancement of the air‐water interfacial transfer of I₂ by reaction with I^? was investigated in order to evaluate a mechanistic model. Separate systems for evaporation and absorption of I₂ were studied. The overall mass transfer coefficient increased from 2 × 10^?4 to 2.5 × 10^?3 cm/s as I^? concentration increased from 10^?4 to 10^?1 M. At I^? concentrations greater than 10^?1 M, the interfacial transfer of I₂ was gas‐side limited. The model gave a good representation of these results.     

Generalized hybrid control synthesis for affine systems using sequential adaptive networks

BACKGROUND: A generalized methodology for the synthesis of a hybrid controller for affine systems using sequential adaptive networks (SAN) is presented. SAN consists of an assembly of neural networks that are ordered in a chronological sequence, with one network assigned to each sampling interval. Using a suitable process model based on oxygen metabolism and an a priori objective function, a hybrid control law is derived that can use online measurements and the states predicted by SAN for computing the desired control action. RESULTS: The performance of the SAN–hybrid controller is tested for simulated fed‐batch production of methionine for three different process conditions. Simulations assume that online measurements of dissolved oxygen (DO) concentration are available. The performance of the SAN–hybrid controller gave an NRMSE of ～10^?4 in the absence of noise, ～10^?3 and ～10^?2 for ± 5% and ± 10% noise in the DO measurement and ～10^?2 for parameter uncertainty when compared with the ideal model prediction. CONCLUSIONS: The observed performance for unmeasured state prediction and control implementation shows that the proposed SAN–hybrid controller can efficiently compute the manipulated variable required to maintain methionine production along the optimized trajectory for different conditions. The test results show that the SAN–hybrid controller can be used for online real‐time implementation in fed‐batch bioprocesses. Copyright © 2009 Society of Chemical Industry     

In‐line mixing for production of citric acid by Candida lipolytica grown on n‐paraffins

This study reports on the effects of internal fermenter and external in‐line agitation and fed‐batch mode of operation on citric acid production from Candida lipolytica using n‐paraffin as the carbon source. An optimum range of fermenter agitation speeds in the range 800–1000 rpm corresponding to Reynolds numbers of 50433–62947 (based on initial batch conditions) seemed to give the best balance between substrate utilization for biomass growth and citric acid production. Proof of concept evidence is presented that indicates that an external in‐line agitator could be used in place of high speed internal agitation to increase citric acid production. However, more work is required to optimize the external agitator concept. Application of multiple fed‐batch feedings can be used to extend the batch fermentation and increase final citric acid concentrations and product yield. Experiments were conducted implementing a three‐cycle fed‐batch process which increased overall citric acid yields to 0.8–1.0 g citric acid g^?1 n‐paraffin, approximately 200% improvement from those found in the normal batch process. The three‐cycle fed‐batch mode of operation also increased the final citric acid concentration to 42 g dm^?3 from about 6 g dm^?3 for normal batch operation. Increased citric acid concentrations in three‐cycle fed‐batch mode was achieved at longer fermentation times. Copyright © 2004 Society of Chemical Industry     

Recovery of 2,4‐dichlorophenol from acidic aqueous streams by Membrane Aromatic Recovery System (MARS)

This study describes the successful recovery of 2,4‐dichlorophenol (DCP) from wastewater using the Membrane Aromatic Recovery System (MARS). In the MARS process a non‐porous membrane separates a wastewater stream and a stripping solution. DCP is extracted from the wastewater and concentrated in its ionic form in the stripping solution, with pH ? pK_a DCP. The MARS extraction stage was operated in batch mode with the stripping solution placed inside, and the wastewater stream outside, the membrane tubes. Advantages of this configuration are avoidance of membrane blockage, reduction of stripping solution volume and operational flexibility. The stability and mass‐transfer characteristics of two different membrane materials, poly(dimethylsiloxane) (PDMS) and ethylene–propylene diene terpolymer (EPDM), were tested in DCP solutions with different acidities in order to simulate real industrial waste streams. EPDM exhibits one order of magnitude lower mass‐transfer rates than PDMS (1.4 × 10^?7 m s^?1 vs 20 × 10^?7 m s^?1 at 30 °C and 2.4 × 10^?7 m s^?1 vs 39 × 10^?7 m s^?1 at 60 °C), however its higher resistance to acid attack provides higher membrane lifetimes. This can be crucial for MARS processes treating real acidic industrial wastewater. A 97% recovery of DCP with a water content of 15 wt% was obtained upon neutralisation of the stripping solution. Copyright © 2004 Society of Chemical Industry     

Lovastatin production by Aspergillus terreus in a two‐staged feeding operation

BACKGROUND: Lovastatin is known to inhibit its own synthesis in the fungus Aspergillus terreus. Therefore, the use of a fermentation strategy that continuously removes some of the lovastatin produced from the bioreactor can enhance its productivity. This paper reports on the effects of dilution rate and the composition of the feed medium on lovastatin production by A. terreus. RESULTS: The feeding strategy consisted of an initial batch/fed‐batch phase and a semi‐continuous culture phase in which the pelleted biomass was retained inside a slurry bubble column. A nitrogen‐free medium was fed at various fixed dilution rates in the semi‐continuous phase. In experiments that were designed to assess the effects of the composition of the medium, the dilution rate was held at 0.42 d^?1, but different feed media were used in separate runs. The best two‐staged production strategy was shown to consist of a 96 h batch/fed‐batch phase that used a nutritionally complete medium. This was followed by a semi‐continuous operation using a medium that was free of both nitrogen and carbon sources. CONCLUSION: Semi‐continuous operation enhanced productivity of lovastatin by 315% compared with a conventional batch operation. The optimal dilution rate in semi‐continuous operation was about 0.42 d^?1. Copyright © 2008 Society of Chemical Industry     

A New Sensor for Determination of Anionic Surfactants in Detergent Products with Carbon Nanotubes as Solid Contact

A new solid‐state sensor for potentiometric determination of surfactants with a layer of multi‐walled carbon nanotubes was prepared. As a sensing material, 1,3‐didecyl‐2‐methylimidazolium–tetraphenylborate ion‐pair was used. The investigated sensor showed a Nernstian response for both dodecylbenzenesulphonate (DBS, 57.6 mV/decade of activity between 5 × 10^?7 to 1 × 10^?3 M) and sodium lauryl sulfate (LS, 58.4 mV/decade of activity between 2 × 10^?7 to 2 × 10^?3 M). It responded in 8–10 s for each ten‐fold concentration change in the range of 1 × 10^?6 to 3 × 10^?3 M. The detection limits for DS and DBS were 2 × 10^?7 and 3 × 10^?7 M, respectively. The sensor revealed a stable response (signal drift 2.6 mV/h) and exhibited satisfactory selectivity performances for LS over most of the anions generally used in surfactant‐based commercial detergents. The main application of this sensor was the end‐point determination in potentiometric titrations of anionic surfactants. The (diisobutyl phenoxy ethoxy ethyl)dimethyl benzyl ammonium chloride (Hyamine), cetyltrimethylammonium bromide, hexadecylpyridinium chloride monohydrate (HDPC) and 1,3‐didecyl‐2‐methylimidazolium chloride were tested as potential cationic titrants, and all exhibited analytically usable titration curves with well‐defined equivalence points. The standard solution of HDPC was used as a cationic titrant by all potentiometric titrations. The operational life‐time of the sensor described was prolonged to more than 3 months.     

Development of a mathematical model for Bacillus circulans growth and alkaline protease production kinetics

BACKGROUND: An unstructured mathematical model was developed to understand information on the relationship between Bacillus circulans growth and metabolism‐related protease production (using logistic and Luedeking–Piret equations respectively) in a batch reactor with respect to glucose consumption and fermentation time. The objective was to develop an indispensable tool for the optimisation, control, design and analysis of alkaline protease production. RESULTS: Biomass growth and enzyme production titres changed with a change in substrate concentration. Modelling analysis of biomass and enzyme production titres at different substrate concentrations revealed significant accuracy in terms of statistical consistency and robustness with respect to fermentation kinetic profiles. CONCLUSION: With the B. circulans strain used, an economic protease yield (2837 × 10³ U g^?1) with respect to biomass and glucose ratio was achieved at low substrate concentration (10 g L^?1). The developed model could be effectively utilised for designing, controlling and up‐scaling the protease production process in high‐density fermentation in selected bioreactors with statistical consistency. Copyright © 2008 Society of Chemical Industry     

Tomography images to analyze the deformation of the cavern in the continuous‐flow mixing of non‐Newtonian fluids

Tomography, an efficient nonintrusive technique, was employed to visualize the flow in continuous‐flow mixing and to measure the cavern volume (V_c) in batch mixing. This study has demonstrated an efficient method for flow visualization in the continuous‐flow mixing of opaque fluids using two‐dimensional (2‐D) and 3‐D tomograms. The main objective of this study was to explore the effects of four inlet‐outlet configurations, fluid rheology (0.5–1.5% xanthan gum concentration), high‐velocity jet (0.317–1.660 m s^?1), and feed flow rate (5.3 × 10^?5?2.36 × 10^?4 m³ s^?1) on the deformation of the cavern. Dynamic tests were also performed to estimate the fully mixed volume (V_{fully mixed}) for the RT, A310, and 3AM impellers in a continuous‐flow mixing system, and it was found that V_{fully mixed} was greater than V_c. Incorporating the findings of this study into the design criteria will minimize the extent of nonideal flows in the continuous‐flow mixing of complex fluids and eventually improve the quality of end‐products. © 2013 American Institute of Chemical Engineers AIChE J, 60: 315–331, 2014     

Adsorption equilibrium,thermodynamics, kinetics,mechanism and process design of zinc(II) ions onto cashew nut shell

Cashew nut shell (CNS) is an agricultural waste was investigated as a new adsorbent for the removal of zinc(II) from aqueous environment. Effects of solution pH, CNS dose, contact time, initial zinc(II) concentration and temperature on removal efficiency were tested and optimum conditions were evaluated. The equilibrium data were fitted well with Langmuir isotherm model and pseudo‐second‐order kinetic model. Langmuir monolayer adsorption capacity of CNS was examined as 24.98 mg/g. Changes in standard Gibbs free energy (?G°), standard enthalpy (?H°) and standard entropy (?S°) showed that the sorption of zinc(II) ions onto CNS are spontaneous and exothermic at 303–333 K. Sorption process was found to be controlled by both surface and pore diffusion. A batch adsorber was designed for different CNS dose to effluent volume ratios using Langmuir equation. Effective diffusivity values were found to be 1.927 × 10^?11 (10 mg/L), 2.135 × 10^?11 (20 mg/L), 2.267 × 10^?11 (30 mg/L), 2.305 × 10^?11 (40 mg/L) and 2.362 × 10^?11 (50 mg/L) m²/s. © 2011 Canadian Society for Chemical Engineering     

Production of Bacillus thuringiensis‐based biopesticides in batch and fed batch cultures using wastewater sludge as a raw material

Bacillus thuringiensis subsp kurstaki was grown in batch and fed batch cultures using wastewater sludge as a raw material. A simple fed batch strategy based on dissolved oxygen measurement during the fermentation cycle was developed in this work. It was established that while shifting the process strategy from batch to fed batch, the maximum spore concentration was increased from 5.62 × 10⁸ to 8.6 × 10⁸ colony forming units per cm³ and resulted in an increase of entomocidal activity from 13 × 10⁹ to 18 × 10⁹ spruce budworm potency units per dm³. Higher entomotoxicity was recorded at low spore concentration using wastewater sludge as a raw material whereas low entomotoxicity was reported at high spore concentration in synthetic medium. Copyright © 2005 Society of Chemical Industry     

Lysine Adsorption on Cation Exchange Resin. IV. Temperature Effects on Equilibrium and Kinetics in Batch and Column Systems

Abstract

Ion exchange equilibria and kinetics are determined for lysine adsorption on the strong acid cation exchanger DIAION SK‐1B at temperatures of 25, 40, and 60°C. The ion exchange equilibrium is found to be independent of temperature. Conversely, the kinetics of ion exchange increases dramatically as the temperature is increased. Average ion exchange selectivity coefficients of 6.0 g/cm³ and 0.52 are obtained for the ion exchange of divalent and monovalent cationic lysine with hydrogen ion, respectively. Resin phase diffusivities are determined by fitting batch binary ion‐exchange data with a mass transfer model based on the Nernst‐Planck equations. As the temperature is increased from 25 to 60°C, the resin phase diffusivity increases from 0.04×10^?6 to 0.14×10^?6 cm²/s for divalent lysine and from 0.16×10^?6 to 0.55×10^?6 cm²/s for monovalent lysine. The combination of temperature‐independent ion exchange equilibria and faster mass transfer at higher temperatures results in higher dynamic binding capacity and more efficient desorption of lysine when ion exchange is operated at an elevated temperature. This behavior is confirmed by means of column adsorption/desorption experiments whose results are found to be in agreement with a model incorporating the equilibrium and mass transfer data obtained in this work.