Novel reactor for aqueous-organic two-phase biocatalysis: A packed bed hollow fiber membrane bioreactor

Summary Hollow fiber membranes were potted in a tubular shell with a particulate, microporous, enzyme bearing support packed in the shell space. A bicontinuous system was thus formed with the reactants, supplied through the shell and the fiber lumen, forming an interface at the surface of the particles. Acid production rates, without any reactor optimization, up to four times greater than with membrane reactors were obtained during the lipase catalyzed hydrolysis of ethyl laurate and olive oil.     

Controlled shear affinity filtration (CSAF): a new technology for integration of cell separation and protein isolation from mammalian cell cultures

Up-flow anaerobic sludge blanket (UASB) reactors are being used with increasing regularity all over the world, especially in India, for a variety of wastewater treatment operations. Consequently, there is a need to develop methodologies enabling one to determine UASB reactor performance, not only for designing more efficient UASB reactors but also for predicting the performance of existing reactors under various conditions of influent wastewater flows and characteristics. This work explores the feasibility of application of an artificial neural network-based model for simulating the performance of an existing UASB reactor. Accordingly, a neural network model was designed and trained to predict the steady-state performance of a UASB reactor treating high-strength (unrefined sugar based) wastewater. The model inputs were organic loading rate, hydraulic retention time, and influent bicarbonate alkalinity. The output variables were one or more of the following, effluent substrate concentration (Se), reactor bicarbonate alkalinity, reactor pH, reactor volatile fatty acid concentration, average gas production rate, and percent methane content of the gas. Training of the neural network model was achieved using a large amount of experimentally obtained reactor performance data from the reactor mentioned above as the training set. Training was followed by validation using independent sets of performance data obtained from the same UASB reactor. Subsequently, simulations were performed using the validated neural network model to determine the impact of changes in parameters like influent chemical oxygen demand (COD) concentration and hydraulic retention time on the reactor performance. Simulation results thus obtained were carefully analyzed based on qualitative understanding of UASB process and were found to provide important insights into key variables that were responsible for influencing the working of the UASB reactor under varying input conditions.     

Lipase-catalyzed hydrolysis of olive oil in chemically-modified AOT/isooctane reverse micelles in a hollow fiber membrane reactor

The hydrolysis of olive oil catalyzed by Candida rugosa lipase in sodium bis(2-ethylhexyl)sulfosuccinate (AOT)/isooctane and the synthetic sodium bis(2-ethylhexyl polyoxyethylene)sulfosuccinate (MAOT)/isooctane reverse micellar systems was investigated in a polysulfone hollow fiber membrane reactor with recycle of the reaction mixture. Lipase was completely retained by the membrane while olive oil and oleic acid freely passed through. The retention of reverse micelles depended on W ₀ (molar ratio of water to surfactant). At an olive oil concentration of 0.23 mol l^–1 the final substrate conversion in the MAOT micellar system was about 1.4 times of that in the AOT micellar system.     

Hydrolysis of triglyceride by the whole cell of Pseudomonas putida 3SK in two-phase batch and continuous reactors systems

Batch and continuous hydrolysis of olive oil in an organic-aqueous two-phase system using the live whole cell of Pseudomonas putida 3SK as a source of a lipase is investigated. The strain was not only fully viable and grown well, but also produced extracellular lipase simultaneously. The degree of hydrolysis, depending on olive oil concentration in the solvents, was maximal at 13.5% (w/v) and decreased with the increase of the substrate concentration. At the optimal condition, a degree of hydrolysis higher than 95% was achieved with 24 h at 30 degrees C when the reaction was carried out in a two-phase batch stirred reactor. For long-term operation a continuous stirred reactor was designed. When the reaction was carried out in a continuous stirred reactor, the degree was hydrolysis reached 86% at a dilution rate of 0.2 h(-1). Satisfactory performance of a two-phase bioreactor was obtained in a long-term continous operation, which lasted for at least 30 days by feeding organic solvent containing olive oil and aqueous media separately. (c) 1994 John Wiley & Sons, Inc.     

Optimization of maltodextrin hydrolysis by glucoamylase in a batch reactor

The hydrolysis of maltodextrins (10 DE) by glucoamylase was studied in a batch reactor at temperatures between 40 and 80 degrees C and substrate concentration range from 17 to 300 kg/m(-3). The experimental data were fitted to a model including thermal deactivation of the enzyme. In the model, the reaction rate was correlated with an extended Michaelis-Menten equation including inhibition by product, and the thermal deactivation of glucoamylase was fitted with a first-order reaction. The dependence of rate parameters on temperature was correlated using the Arrhenius equation. The differential equation of the model was integrated and the optimal enzyme demand and temperature were determined for isothermal operation.     

Performance of the continuous glucose isomerase reactor system for the production of fructose syrup

Glucose isomerase in the form of heat-treated whole-cell enzyme prepared from Streptomyces phaeochromogenus follows the reversible single-substrate reaction kinetics in isomerization of glucose to fructose. Based on the Kinetic constants determined and the mathematical model of the reactor system developed, the preformance of a plug-flow-type continuous-enzyme reactor system was studied experimentally and also simulated with the aid of a computer for the ultimate objective of optimization of the glucose isomerase reactor system. The enzyme decay function for both the enzyme storage and during the use in the continuous reactor, was found to follow the first-order decay kinetics. When the enzyme decay function is taken into consideration, the ideal homogeneous enzyme reactor kinetics provided a satisfactory working model without further complicatin of the mathematical model, and the results of computer simulation were found to be in good agreement with the experimental results. Under a given set of constraints the performance of the continuous glucose isomerase reactor system can be predicted by using the computer simulation method described in this paper. The important parameters studied for the optimization of reactor operation were enzyme loading, mean space time of the reactor, substrate feed concentration, enzyme decay constants, and the fractional conversion, in addition to the kinetic constants. All these parameters have significant effect on the productivity. Some unique properties of the glucose isomerization reaction and its effects on the performance of the continuous glucose isomerase reactor system have been studied and discussed. The reaction kinetics of glucose isomerase and the effects of both the enzyme loading and the changes in reaction rate within a continuous reactor on the productivity are all found to be of particular importance to this enzyme reactor system.     

Transient response of encapsulated enzymes in hollow-fiber reactor

A mathematical model for the transient response of encapsulated enzymes is developed showing the effects of the outer boundary layer, the encapsulating membrane, the partition coefficient, and diffusion with reaction within the encapsulating medium. The model incorporates both first-order kinetics and Michaelis-Menten kinetics for the reaction rate. Using typical hollow-fiber or microcapsule parameters, the model shows that (a) the partition coefficient affects the overall rate only when the rate-limiting step is diffusion through the membrane, (b) the transient overall effectiveness factor rises sharply with time and approaches an asymptotic value for most situations, and (c) the first-order approximation to Michaelis-Menten kinetics is not valid when the initial outside bulk concentration is higher than the Michaelis constant and the overall rate is reaction limited. The model is compared with experimental data using uricase in a hollow-fiber enzyme reactor configuration. Batch assay and CSTUER (continuous-stirred ultrafiltration enzyme reactor) studies were conducted on the free enzyme to provide some of the parameters used in the model. The CSTUER data fit the case of substrate inhibition kinetics with the apparent Michaelis constant approaching zero. The hollow-fiber reactor was conducted with uricase dissolved in both a buffer solution and a concentrated hemoglobin solution. Diffusivities of the solute were measured in both solutions as was the osmotic pressure of the hemoglobin solution. While experimental data for uricase in buffer solution could easily be matched by the model, that in the concentrated hemoglobin solution could not.     

Hydrolysis of olive oil catalyzed by surfactant-coated<Emphasis Type="Italic">Candida rugosa</Emphasis> lipase in a hollow fiber membrane reactor

In this study, we invetigated the hydrolysis of olive oil catalyzed by a surfactant-coatedCandida rugosa lipase in a hydrophilic polyacrylonitrile hollow fiber membrane reactor and then compared the results to those using the native lipase. The organic phase was passed through the hollow inner fibers of the reactor and consisted of either the coated lipase and olive oil dissolved in isooctane or the coated lipase dissolved in pure olive oil. The aqueous phase was pumped through the outer space. After 12 h and with conditions of 30°C, 0.12 mg enzyme/mL and 0.62 M olive oil, the substrate conversion of the coated lipase reached 60%. This was twice the conversion for the same amount of native lipase that was pre-immobilized on the membrane surface. When using pure olive oil, after 12 h the substrate conversion of the coated lipase was 50%. which was 1.4 times higher than that of the native lipase.     

Performance test of a 6-stage continuous reactor for palm methyl ester production

Effects of residence time (3-12 min), stirrer speed (0-800 rpm), and NaOH concentration (0.25-1.0 wt% of oil) on the production performance of the designed 6-stage continuous reactor (2.272 l) for transesterification of palm oil were investigated at molar ratio of methanol to oil of 6:1 and temperature of 60 degrees C. Higher stirrer speed increased the reaction rate up to an appropriate speed but excessive stirrer speed decreased the reaction rate. Inappropriate stirrer speed runs dramatically decreased the production capacity of the reactor. Higher NaOH concentration significantly increased reaction rate and production capacity of the reactor. The reactor had a residence time distribution equivalent to 5.98 ideal CSTRs in series and a production performance equivalent to a plug flow reactor. At NaOH of 1.0 wt% of oil, the reactor could produce saleable biodiesel within residence time of 6 min in which a production capacity was 17.3 l/h and a power consumption of stirrer was 0.6 kW/m(3).     

Mathematical modeling of diffusion and reaction in the hydrolysis of vegetable protein in an immobilized enzyme recycle reactor

Experimental investigation is by far the most effective approach for studying the behavior of physical systems. However, an enzymatic solubilization of vegetable protein is a complex combination of intrinsic problems, of which many are not easily adaptable to experimental investigation. Experimental designs to study enzyme vegetable protein reactions yield data which describe the extramembraneous activity of the immobilized enzyme. In a continuous recycle immobilized enzyme reactor, the microenvironment concentration of the substrate or product in the membrane phase, or the concentrations along the reactor axial length in the bulk phase are not discernible to the experimenter. However, the knowledge of such concentration profiles is important in weighing the significance of such factors as intermembrane diffusion, enzyme loading, wet membrane size, and the mode of operation of the reactor. The simulation of mathematical models, which describe the physical system within the constraints imposed, yields information which is vital to the understanding of the process occurring in the reactor. The kinetics and diffusion of an immobilized thermophilic Penicillium duponti enzyme at pH 3.4-3.7 and 50 degrees C was modeled mathematically. The kinetic parameters were evaluated by fitting a model to experimental data using nonlinear regression analysis. Simulation profiles of the effects of reactor geometry, substrate concentration, membrane thickness, and enzyme leading on the hydrolysis rate are presented. From the profiles generated by the mathematical model, the best operational reactor strategy is recommended.     

Modeling pyrolysis oil production in an entrained-flow reactor

Experimental oil yields obtained from the operation of an entrained-flow pyrolysis reactor using oak as the feed are presented. In addition, a model of the reactor based on the numerical solution of simultaneous differential equations is discussed. Model predictions for oil yields are given and compared with experimental results. Although the maximum oil yield for all experimental runs reported is 51%, the model indicates that oil yields as high as 60% are possible.     

Systematic simulation of a tubular recycle reactor on the basis of pilot plant experiments

Systematic simulation may decisively help in development and optimization of bioprocesses. By applying simulation techniques, optimal use can be made of experimental data, decreasing development costs and increasing the accuracy in predicting the behavior of an industrial scale plant.The procedure of the dialogue between simulation and experimental efforts will be exemplified in a case study. Alcoholic fermentation of glucose by zymomonas mobilis bacteria in a gasified tubular recycle reactor was studied first by systematic simulation, using a computer model based solely on literature data. On the base of the results of this simulation, a 0.013 m³ pilot plant reactor was constructed. The pilot plant experiments, too, were based on the results of the systematic simulation.Simulated and experimental data were well in agreement. The pilot plant experiments reiterated the trends and limits of the process as shown by the simulation results. Data from the pilot plant runs were then used to improve the simulation model. This improved model was subsequently used to simulate the performances of an industrial scale plant. The results of this simulation are presented. They show that the alcohol fermentation in a tubular recycle reactor is potentially advantageous to other reactor configurations, especially to continuous stirred tanks.List of Symbols CPFR Continous plug flow reactor - CST R Continous stirred tank reactor - CTR Continous tubular reactor - FMC Fermentation micro computer - P kg/m³ Product concentration - S kg/m³ Glucose concentration - S _o kg/m³ Glucose concentration in the feed - X kg/m³ Biomass concentration - z Cell damage     

Mathematical model for a three-phase fluidized bed biofilm reactor in wastewater treatment

A mathematical model for a three phase fluidized bed bioreactor (TFBBR) was proposed to describe oxygen utilization rate, biomass concentration and the removal efficiency of Chemical Oxygen Demand (COD) in wastewater treatment. The model consisted of the biofilm model to describe the oxygen uptake rate and the hydraulic model to describe flow characteristics to cause the oxygen distribution in the reactor. The biofilm model represented the oxygen uptake rate by individual bioparticle and the hydrodynamics of fluids presented an axial dispersion flow with back mixing in the liquid phase and a plug flow in the gas phase. The difference of settling velocity along the column height due to the distributions of size and number of bioparticle was considered. The proposed model was able to predict the biomass concentration and the dissolved oxygen concentration along the column height. The removal efficiency of COD was calculated based on the oxygen consumption amounts that were obtained from the dissolved oxygen concentration. The predicted oxygen concentration by the proposed model agreed reasonably well with experimental measurement in a TFBBR. The effects of various operating parameters on the oxygen concentration were simulated based on the proposed model. The media size and media density affected the performance of a TFBBR. The dissolved oxygen concentration was significantly affected by the superficial liquid velocity but the removal efficiency of COD was significantly affected by the superficial gas velocity. An erratum to this article can be found online at .     

Multimolecular process in a packed-bed immobilized enzyme reactor: numerical simulation and back-mixing effects.

In a previous report, we presented a new analytical model describing the performance of a packed-bed catalytic unit, where the reaction between two cosubstrates is catalyzed by an enzyme immobilized on a porous carrier. The model explicitly takes into account the changes in concentrations of both cosubstrates along the reactor, as well as the hydrodynamic regimen (i.e., back-mixing) prevailing in the packed bed. In the present report, and on the basis of the procedures developed, we present a detailed analysis of the performance of the reactor. With numerical simulations, the effects of internal diffusion limitations, the depth of the pores, the substrates' concentration in the feed, and kinetic parameters are evaluated. Particular attention is also given here to the back-mixing effects prevailing in the reactor. An experimental procedure for assessing their extent is described.     

Hydrolysis of liquefied corn starch in a membrane reactor

The objective of this study was to develop a continuous hydrolysis process for the enzymatic saccharification of liquefied corn starch using a membrane reactor. A residence time distribution study confirmed that the membrane reactor could be modeled as a simple continuous stirred tank reactor (CSTR). Kinetic studies indicated that the continuous reactor operated in the first-order region with respect to substrate concentration at substrate concentrations greater than 200 g/L. At a residence time of 1 h and an enzyme concentration of 1 g/L, the maximum reaction velocity (V(m)) was 3.86 g glucose/L min and the apparent Michaelis constant (K(m) (')) was 562 g/L. The K(m) (') value for the continuous reactor was 2-7 times greater than that obtained in a batch reactor.Kinetic data were fit to a model based on the Michaelis-Menten rate expression and the design equation for a CSTR. Application of the model at low reactor space times was successful. At space times of 6 min or less, the model predicted the reactor's performance reasonably well. Additional work on the detection and quantitation of reversion products formed by glucoamylase is required. Isolation, detection, and quantitation of reversion products by HPLC was difficult. Detailed analysis on the formation of these reversion products could lead to better reactor designs in the future.     

An immobilized cell reactor with simultaneous product separation. I. Reactor design and analysis

A four-phase reactor-separator (gas, liquid, solid, and immobilized catalyst) is proposed for fermentations characterized by a volatile product and nonvolatile substrate.In this reactor, the biological catalyst is immobilized onto a solid column packing and contacted by the liquid containing the substrate.A gas phase is also moved through the column to strip the volatile product into the gas phase. The Immobilized Cell Reactor-Separator (ICRS) consists of two basic gas-liquid flow sections: a cocurrent "enricher" followed by a countercurrent-"stripper".In this article, an equilibrium stage model of the reactor is developed to determine the feasibility and important operational variables of such a reactor-separator. The ICRS concept is applied to the ethanol from whey lactose fermentation using some preliminary immobilized cell reactor performance data. A mathematical model for a steady-state population based on an adsorbed monolayer of cells is also developed for the reactor. The ICRS model demonstrated that the ICRS should give a significant increase in reactor productivity as compared to an identically sized Immobilized Cell Reactor (ICR) with no separation. The gas-phase separation of the product also allows fermentation of high inlet substrate concentrations. The model is used to determine the effects of reactor parameters on ICRS performance including temperature, pressure, gas flow rates, inlet substrate concentration, and degree of microbial product inhibition.     

Production of lipolyzed butteroil by a calf pregastric esterase immobilized in a hollow fiber reactor: III. Effect of glycerol

Lipolysis of butter oil in a hollow fiber reactor containing an immobilized calf pregastric esterase was studied at 40 degrees C, a pH of 6.0, and glycerol concentrations of 0, 150, and 500 g/L in the buffer solution. The concentrations of 10 fatty acid species in the lipolyzed product were determined using high-performance liquid chromatography. The rate of loss of enzyme activity and the relative selectivities of this esterase depended on the glycerol concentration. By contrast, the overall rate of release of fatty acids was not affected by the glycerol concentration. Loss of enzyme activity was modeled using first-order kinetics. The models for deactivation and reaction kinetics were fit simultaneously to the data. The model was successful in describing the rates of release of all 10 fatty acid species for a range of space times from 0 to 25 h. The parameters of the model were tested for dependence on glycerol concentration.     

Mathematical and kinetic modeling of biofilm reactor based on ant colony optimization

Inverse estimation of model parameters via mathematical modeling route, known as inverse modeling (IM), is an attractive alternative approach to the experimental methods. This approach makes use of efficient optimization techniques in the course of solution of an inverse problem with the aid of measured data. In this study, a novel optimization method based on ant colony optimization (ACO), denoted by ACO-IM, is presented for inverse estimation of kinetic and film thickness parameters of biofilm models that describe an experimental fixed bed anaerobic reactor. The proposed optimization method for parameter estimation emulates the fact that ants are capable of finding the shortest path from a food source to their nest by depositing a trial of pheromone during their walk. The efficacy of the ACO-IM for numerical estimation of bio-kinetic parameters is demonstrated through its application for the anaerobic treatment of industry wastewater in a fixed bed biofilm process. The results explain the rigorousness of mathematical models, the form of kinetic and film thickness models and the type of packing to be used with the biofilm process for accurate determination of kinetic and film thickness parameters so as to ensure reliable predictive performance of the biofilm reactor models.     

Mixing and phase hold-ups variations due to gas production in anaerobic fluidized-bed digesters: influence on reactor performance

The influence of mixing and phase hold-ups on gas-producing fluidized-bed reactors was investigated and compared with an ideal flow reactor performance (CSTR). The liquid flow in the anaerobic fluidized bed reactor could be described by the classical axially dispersed plug flow model according to measurements of residence time distribution. Gas effervescence in the fluidized bed was responsible for bed contraction and for important gas hold-up, which reduced the contact time between the liquid and the bioparticles. These results were used to support the modeling of large-scale fluidized-bed reactors. The biological kinetics were determined on a 180-L reactor treating wine distillery wastewater where the overall total organic carbon uptake velocity could be described by a Monod model. The outlet concentration and the concentration profile in the reactor appeared to be greatly influenced by hydrodynamic limitations. The biogas effervescence modifies the mixing characteristics and the phase hold-ups. Bed contraction and gas hold-up data are reported and correlated with liquid and gas velocities. It is shown that the reactor performance can be affected by 10% to 15%, depending on the mode of operation and recycle ratio used. At high organic loading rates, reactor performance is particularly sensitive to gas effervescence effects. Copyright 1998 John Wiley & Sons, Inc.