Adsorptive separation of fructose and glucose from an agroindustrial waste of cashew industry

Nearly all agroindustrial wastes have appreciable sugar content including cashew apples (Anacardium occidentale, L.), which are an important sub-utilized biomass source in Northeastern Brazil. Adsorption in fixed bed, both in batch and continuous modes, is a low-cost separation technique, which has been widely used in the concentration, separation and purification of bioproducts, such as sugars. The present work is an experimental study aimed at measuring responses in fixed bed, needed for design purposes. Two commercial ion-exchange resins were studied: DOWEX Monosphere 99/Ca and DIAION UBK555. The adsorbents showed linear isotherms for both sugars with marked selectivity for fructose (2.2 for DOWEX and 1.5 for DIAION). A mathematical model was used to estimate kinetic parameters and predict breakthrough behaviour of binary solutions and complex feeds. The kinetics of mass transfer was well described by a linear driving force approximation (LDF) and estimated kinetic constants were around 1 min(-1). The results indicate that the use of independent experiments with synthetic monocomponent solutions leads to reliable parameters, and the model is capable to foresee reasonably well the breakthrough curve of the sugars present in the juice, under different purification conditions. The use of complex feeds led to overshoot behaviour, possibly due to the irreversible adsorption of oligosaccharides.     

Theoretical investigation of axial and local particle size distribution on expanded bed adsorption process

The general rate model was developed and solved to describe protein adsorption in an expanded bed. The model takes into account axial variation of bed porosity, particle size distribution (PSD), external and intraparticle mass transfer, and dispersion in liquid and solid phase. The analysis of the influence of the model parameters on dynamic capacity (DC) was investigated. The simulation results showed that major impact on dynamic capacity is exerted by intraparticle mass transfer (particle diameter and pore diffusivity). The external mass transfer resistance and dispersion parameters have secondary effect on DC. The replacement of axial PSD by the mean particle diameter results in error in calculation of DC, which increases remarkably with the increase of mean particle diameter. The PSD can promote a very slow approaching of plateau concentration by breakthrough curves. It was shown also that axial bed porosity variation could be replaced by average porosity with negligible error for DC calculations.     

Cadmium uptake by algal biomass in batch and continuous (CSTR and packed bed column) adsorbers

In this work, the properties of marine algae Gelidium, algal waste from agar extraction industry and a composite material were investigated for cadmium(II) biosorption. Equilibrium experiments were performed at three pH values (4, 5.3 and 6.5). Equilibrium data were well described by the Langmuir and Langmuir–Freundlich isotherms. Two models predicting the pH influence in the cadmium biosorption (discrete and continuous models) have been developed in order to better describe the equilibrium. The continuous model also considers a heterogeneous distribution of carboxylic groups, determined by potentiometric titration. The results of batch kinetic experiments performed at different pH values were well fitted by two mass transfer models and the homogeneous diffusion coefficients for the cadmium ions inside the biosorbent were obtained. Continuous stirred tank reactor (CSTR) and packed bed column configurations were also examined for the biosorption of cadmium ions. A strong acid (0.1 M HNO₃) was used as eluant to regenerate the biosorbents in the column. Several mass transfer models were applied with success to describe the biosorption process in batch mode, CSTR and fixed bed column.     

Effect of biocatalyst swelling on the operation of packed-bed immobilized enzyme bioreactor

A general mathematical model was developed for predicting the performance and simulation of a packed-bed immobilized enzyme reactor performing a reaction that follows Michaelis–Menten kinetics with competitive product inhibition. The performance of a packed-bed immobilized enzyme reactor was analyzed taking into account the effect of bed swelling on various diffusional phenomena such as axial dispersion, internal and external mass transfer limitations. The numerical solutions were compared with experimental data obtained for a packed-bed reactor operating with β-galactosidase entrapped in Ca-alginate-K-κ-carrageenan gels for lactose hydrolysis.     

Biosorption Processes for Natural and Waste Water Treatment – Part II: Experimental Studies and Theoretical Model of a Biosorption Fixed Bed

A model has been developed for fixed‐bed biosorption performance, i.e. combined action of adsorption of organic water contaminants and their biological destruction in a column. The model contains an adsorption isotherm of the Freundlich type, adsorption kinetics by an overall film mass transfer (Glueckauf equation), maximum bacterial growth,and biological aerobic destruction (Monod model) of the organics by exoenzymes. Bacteria can not penetrate into the pores of the adsorbent. The model was tested using the system aqueous solution of aniline/Pseudomonas putida/Polysorb 40/100. Breakthrough curves in shorter columns have been measured and a velocity‐dependent steady‐state exit concentration was achieved. These curves could be simulated with sufficient accuracy on the basis of isotherm data, mass transfer coefficients and values of biological growth and destruction activity estimated from independent measurements.     

Gas-liquid mass transfer in bioreactor with three-phase inverse fluidized bed

In the present study the oxygen mass transfer from the gas to the aqueous phase in a Three-Phase Inverse Fluidized Bed (TPIFB) has been studied. A pilot scale TPIFB has been designed and constructed. For determination of the volumetric oxygen mass transfer coefficient the elegant dynamic method, described by Dang et al. (1977) was used. The influence of hydrodynamic parameters, e.g., superficial velocities of the gas and liquid phases on the mass transfer rate was studied. In the range of variables covered, it was found that the superficial liquid velocity had a weak effect on the mass transfer whereas the gas flowrate affects the mass transfer positively. The results for the volumetric oxygen transfer coefficient in the TPIFB were compared to reported values of that coefficient, measured in a classic three-phase fluidised bed under similar hydrodynamic conditions and solid phase properties. The comparison demonstrated a two-fold increase of the oxygen transfer rate in the inverse bed over that in the classic one.     

Dynamic model of a nitrifying fixed bed column: Simulation of the biomass distribution of Nitrosomonas and Nitrobacter and of transient behaviour of the column

A dynamic model for a fixed bed nitrifying column with recirculation of the liquid and gas phases was developed. Liquid RTD experiments demonstrated that the liquid phase was perfectly mixed inside the column. Hete- rogeneity of biomass distribution on the solid phase (beads) was represented by an N-tanks in series model, and a back-mixing term was set to account for the well-mixed liquid phase throughout the column. In autotrophic conditions, competition for oxygen is the cause of the spatial segregation of the two species. Nitrosomonas is concentrated on beads at the bottom of the bed whereas Nitrobacter is more widely distributed. This is consistent with biomass distribution results reported by Cox et al. [17] in a nitrifying fixed bed column. Nitrification takes place at the bottom of the column, always in oxygen gas-liquid mass transfer limiting conditions. Nevertheless, considering the whole process, nitrification is complete (>98% of NH₃ oxidised) and there is no oxygen limitation (the outlet dissolved oxygen concentration is not limiting). The dynamic behaviour of the column, in conditions set up to avoid biofilm diffusion limitation, was simulated for different NH₃-load variations and oxygen shutdowns. The simulated behaviour of the column can be compared to results reported by Bazin et al. [16]. This confirms that the output transient nitrite peaks are higher when changes in the process conditions produce a rearrangement of biomass distribution in the fixed bed.     

Engineered Biofilms for Metal Ion Removal

Firstly, biofilm and biosorbents are defined. Mechanisms of interactions between metal ions and biofilm are discussed in terms of diffusion, mass transfer and sorption. In a second step, different processes using biofilm to remove heavy metal in aqueous solutions are presented. The continuously stirred processes are described for metal ion removal in wastewater by biofilm coating particles. In this case, the equilibrium data obtained with isotherm curves show a good adsorption of several metal ions onto biofilm. Examples of adsorption capacities for a large number of microorganisms and heavy metal ions are presented. The fixed bed reactors packed with grains coated with a biofilm are efficient to get a sorption (adsorption or ion exchange) of cations. The pressure drop is calculated with classical equations. Some values such as adsorption capacities and breakthrough times are got from the breakthrough curves. Several models (Adams-Bohart, mass transfer, and homogeneous surface diffusion models) are applied to get design data. A new approach using neural network to model breakthrough curves is proposed and discussed.     

Sorbitol and Gluconate Production in a Hollow Fibre Membrane Reactor by Immobilized Zymomonas Mobilis

This study describes the results of a hollow fibre membrane reactor with immobilized treated cells of Zymomonas mobilis which produced sorbitol and gluconic acid continuously from fructose and glucose respectively. A productivity of 10-20 g sorbitol · L^-1 · h^-1 and 10-20 gluconate · L^-1 · h^-1 (based on total bioreactor volume) from a feed of 100 g · L^-1 each of glucose and fructose was possible at high dilution rates. Kinetic parameters describing the reaction rate of treated cells in batch reactors were used to analyse the performance of the hollow fibre membrane reactor employing significant convective mass transfer. No significant mass transfer limitation was apparent.     

Continuous biosynthesis of biodiesel from waste cooking palm oil in a packed bed reactor: optimization using response surface methodology (RSM) and mass transfer studies

This study aimed to develop an optimal continuous procedure of lipase-catalyzes transesterification of waste cooking palm oil in a packed bed reactor to investigate the possibility of large scale production further. Response surface methodology (RSM) based on central composite rotatable design (CCRD) was used to optimize the two important reaction variables packed bed height (cm) and substrate flow rate(ml/min) for the transesterification of waste cooking palm oil in a continuous packed bed reactor. The optimum condition for the transesterification of waste cooking palm oil was as follows: 10.53 cm packed bed height and 0.57 ml/min substrate flow rate. The optimum predicted fatty acid methyl ester (FAME) yield was 80.3% and the actual value was 79%. The above results shows that the RSM study based on CCRD is adaptable for FAME yield studied for the current transesterification system. The effect of mass transfer in the packed bed reactor has also been studied. Models for FAME yield have been developed for cases of reaction control and mass transfer control. The results showed very good agreement compatibility between mass transfer model and the experimental results obtained from immobilized lipase packed bed reactor operation, showing that in this case the FAME yield was mass transfer controlled.     

Kinetics of enzymatic degradation of cyanide

CYANIDASE(@) is a new enzyme preparation capable of degrading cyanide in industrial wastewaters to ammonia and formate in an apparently one-step reaction, down to very low concentrations. This enzyme has both a high selectivity and affinity toward cyanide. A granular form of the biocatalyst was used in a recirculation fixed bed reactor in order to characterize the new biocatalyst with respect to pH, ionic strength, common ions normally present in wastewaters, mass transfer effects, and temperature. Long term stability was investigated. The kinetics of the enzymatic degradation of cyanide were studied in a batch reactor using the powdered immobilized enzyme preparation and modeled using a simple Michaelis-Menten equation.     

Optimal biocatalyst loading in a fixed bed

The optimal distribution of biocatalyst in a fixed bed operating at steady state was determined to minimize the length of the bed for a fixed conversion of 95%. The distribution in terms of the biocatalyst loading on an inert support depends upon the axial distance from the bed entrance (continuous solution) as well as a set of dimensionless parameters that reflect the bed geometry, the bulk flow, reaction kinetics and diffusional characteristics. A mathematical model of the system with the following features was used to obtain the results: (1) convective mass transfer and dispersion in the bulk phase; (2) mass transfer from the bulk phase to the surface of the catalyst particle; and (3) simultaneous diffusion and chemical reaction in the catalyst particle with Michaelis–Menton kinetics and a reliable diffusion model (Zhao and DeLancey in Biotechnol Bioeng 64:434–441, 1999, 2000). The solution to the mathematical model was obtained with Mathematica utilizing the Runge Kutta 4–5 method. The dimensionless length resulting from the continuous solution was compared with the optimal length restricted to a uniform or constant cell loading across the entire bed. The maximum difference in the dimensionless length between the continuous and uniform solutions was determined to be 6.5%. The model was applied to published conversion data for the continuous production of ethanol that included cell loading (Taylor et al. in Biotechnol Prog 15:740–751, 2002). The data indicated a minimum production cost at a catalyst loading within 10% of the optimum predicted by the mathematical model. The production rate versus cell loading in most cases displayed a sufficiently broad optimum that the same (non-optimal) rate could be obtained at a significantly smaller loading such as a rate at 80% loading being equal to the rate at 20% loading. These results are particularly important because of the renewed interest in ethanol production (Novozymes and BBI International, Fuel ethanol: a technological evolution, 2004).     

三相逆流湍动床气液传质性能的研究

由空气-水(清水/废水)-中空玻璃珠构成三相体系,在表观气速0·53~10mm·s-1、固含率为0~0·3、表观液速0~0·2mm·s-1的条件下,采用溶氧仪研究了三相逆流湍动床的气液传质性能,考察了操作参数和液体性质对液相容积传质系数kLa的影响。结果表明,在所试条件下,kLa为0·0456~1·414min-1。kLa随着表观气速和表观液速的增加而增加,随着固含率的增加先增加后减小,0·05~0·08为反应器传质的最优固含率条件。液体性质对kLa有重大影响,高浓度模拟废水和工业废水中的kLa比清水中的kLa分别减小39·0%和50·9%。研究结果可为后续逆流湍动床废水生物处理过程分析与模拟提供传质基础数据。     

Sorbitol and Gluconate Production in a Hollow Fibre Membrane Reactor by Immobilized Zymomonas Mobilis

This study describes the results of a hollow fibre membrane reactor with immobilized treated cells of Zymomonas mobilis which produced sorbitol and gluconic acid continuously from fructose and glucose respectively. A productivity of 10–20 g sorbitol · L^-1 · h^-1 and 10–20 gluconate · L^-1 · h^-1 (based on total bioreactor volume) from a feed of 100 g · L^-1 each of glucose and fructose was possible at high dilution rates. Kinetic parameters describing the reaction rate of treated cells in batch reactors were used to analyse the performance of the hollow fibre membrane reactor employing significant convective mass transfer. No significant mass transfer limitation was apparent.     

A semi-analytical model for dissolved oxygen mass transfer coefficient at the sediment–water interface

Relying on the fundamental principles of mass transport in a turbulent flow, we have developed a semi-analytical model for a mass transfer coefficient in a sediment water interface over a smooth bed. The governing equations with boundary conditions reflect a mechanism of shear dispersion in a turbulent flow. The model is formulated in terms of the Sherwood-Reynolds-Schmidt functional dependence. Unlike previous regression-type models, the mass transfer coefficient at the sediment-water interface is parameterized by the friction coefficient. Flow conditions over a smooth bed ranging in Reynolds number from 1800 to 7000 were used to verify the model. The predicted mass transfer coefficients are in very good agreement with the experimental data.     

Immobilization of a recombinant strain producing glucose isomerase on SiO2-xerogel and properties of prepared biocatalysts

An original method of immobilization of nongrowing microorganism cells on xerogel of silicon dioxide containing insoluble hydroxyl compounds of cobalt(III) has been developed. A recombinant strain producing glucose isomerase has been constructed on the basis of Escherichia coli with the use of a gene of Arthrobacter nicotianae. It was revealed that glucose isomerase activity and stability of biocatalysts prepared on the basis of the recombinant E. coli strain was 3-5 times greater compared with the biocatalysts prepared with the use of the donor strain A. nicotianae. Under conditions of continuous hydrolysis of 3 M fructose at 62-65 degrees C in a fixed bed reactor, time of half-inactivation of the biocatalysts prepared from the recombinant strain and A. nicotianae was -60 and -25 days, respectively.     

The role of sucrose during maturation of black spruce (Picea mariana) and white spruce (Picea glauca) somatic embryos

The present study was conducted to understand the role of sucrose in the medium on the maturation of black spruce and white spruce somatic embryos. A maturation medium containing 6% sucrose, which hydrolyzed into glucose and fructose, gave significantly more embryos than a medium containing 3.16% of each glucose and fructose. Preventing the complete sucrose hydrolysis by a daily transfer of the tissues onto fresh medium significantly decreased the yield of somatic embryos compared to when sucrose was allowed to complete its hydrolysis. This reduction was not due to the manipulation of the tissues during the transfer, since a daily in situ transfer did not affect embryo production. To verify if the better embryo production observed on a medium containing 6% sucrose was due to the increasing osmotic pressure of the medium, this increasing osmotic pressure was simulated with a sequence of media containing different concentrations of glucose and fructose. Unexpectedly and for both species, this simulation did not improve somatic embryo production, which stayed similar to the one obtained on constant osmotic pressure. To understand these results, embryos produced on the different treatments were analyzed in terms of sucrose, glucose, fructose and starch levels and protein contents. The embryo carbohydrate content was independent from the carbohydrate used in the maturation medium. However, embryos matured on 6% sucrose allowed to hydrolyze during the maturation period contained significantly more soluble and insoluble proteins than embryos matured on any other treatment. Furthermore, embryos with a higher protein content also exhibited a higher epicotyl appearance frequency. The role of sucrose as a regulatory factor during the maturation of spruce somatic embryos is discussed.     

Absorption and metabolism of fructose by rat jejunum.

The absorption and metabolism of fructose was investigated in the vascularly perfused jejunum of fructose-fed rats. With 10 mM-glutamate and 10 mM-fructose in the lumen, the viability of the tissue is maintained and fructose is absorbed and utilized at high rates. With 28 mM-fructose in the lumen, glucose appears in the vascular bed. With 10 mM- or 28 mM-fructose in the presence of 10 mM- or mM-glucose in the lumen, the fructose absorption is decreased. From 10 mM- or 28 mM-sucrose in the lumen, fructose uptake is also less than from the equivalent concentration of free fructose. The rate of appearance of fructose in the vascular bed is independent of the source of fructose from which it is derived. In the presence of glucose, either free or as sucrose, there is a marked decrease in the utilization of fructose, defined as the difference between that absorbed by the jejunum and that transported unchanged into the vascular bed. In all cases about half of the carbohydrate absorbed from the lumen is converted into lactate, most of which is secreted into the blood. The absorption of glucose and the rate of vascular appearance of glucose from glucose in the lumen are about 1.5 times greater than those of fructose from fructose in the lumen. It is concluded: firstly, that fructose uptake from the lumen of rat jejunum is determined by its concentration and by the demand for it as a fuel for the intestine, a demand that is severely decreased in the presence of glucose; secondly, that in the vascularly perfused jejunum there is no evident kinetic advantage for uptake of fructose or glucose from sucrose rather than from free monosaccharide in the lumen; thirdly, that some fructose can be converted into glucose.     

Comparative study of ethanol production by an immobilized yeast in a tubular reactor and in a multistage reactor

Summary The productivity of continuous ethanol fermentation has been increased using fixed bed reactors where a high density of yeast cells was maintained on a packing of wood chips. Two different systems have been used: 1. A tubular reactor which produced alcohol solutions containing up to 13.5% (V/V) ethanol. High CO₂ retention and a poor mass transfer between bulk medium and immobilized biomass prevented production rates higher than 2.2 g/l·h. 2. A multistage reactor where a better utilisation of the reactor volume led to improved performances. Solutions containing 132 g/l of ethanol (16.5% V/V) were produced with a productivity increased up to 4.8 g/l·h. A better distribution of the active biomass and a lower gradient of alcohol concentration between support and bulk medium are possible reasons for this improvement.