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Biochemical Engineering Journal (v.39, #3)
Oxygen transfer in hydrocarbon–aqueous dispersions and its applicability to alkane bioprocesses: A review by K.G. Clarke; L.D.C. Correia (pp. 405-429).
Accumulation of alkane by-products from gas to liquid fuel processes presents an attractive feed stock opportunity with potential for bioconversion to a wide variety of valuable commodity products. This review highlights the need to address the complexities of the oxygen transfer rate and overall volumetric oxygen transfer coefficient ( KL a) in hydrocarbon bioprocesses so that this potential can be realised.Three markedly different KL a behavioural trends have been identified in hydrocarbon–aqueous dispersions and characterised according to the hydrocarbon type and concentration, operating conditions and geometric constraints. A fundamental conceptual understanding of the mechanisms which define the exact behaviour of KL a in response to changes in turbulence and fluid properties is provided. Further, the behaviour is quantified in terms of the parameters which underpin this response viz. bubble diameter, gas–liquid interface rigidity, gas hold up, surface tension, viscosity and diffusivity.Consideration is given to existing predictive correlations for interfacial transfer area, bubble diameter, gas hold up, oxygen transfer coefficient and KL a. It is envisaged that through the elucidation and quantification of the parameters which shape the behaviour of KL a, these correlations may be successfully extended to predict the complex behavioural KL a trends in hydrocarbon-based bioprocesses.
Keywords: Alkane bioconversion; Aerobic processes; Gas–liquid transfer; Oxygen transfer; Agitation; Fluid properties
A novel method for the immobilization of glucoamylase onto polyglutaraldehyde-activated gelatin by Aziz Tanriseven; Zehra Ölçer (pp. 430-434).
A novel method was developed for the immobilization of glucoamylase from Aspergillus niger. The enzyme was immobilized onto polyglutaraldehyde-activated gelatin particles in the presence of polyethylene glycol and soluble gelatin, resulting in 85% immobilization yield. The immobilized enzyme has been fully active for 30 days. In addition, the immobilized enzyme retained 90 and 75% of its activity in 60 and 90 days, respectively. The enzyme optimum conditions were not affected by immobilization and the optimum pH and temperature for free and immobilized enzyme were 4 and 65°C, respectively. The kinetic parameters for the hydrolysis of maltodextrin by free and immobilized glucoamylase were also determined. The Km values for free and immobilized enzyme were 7.5 and 10.1gmaltodextrin/l, respectively. The Vmax values for free and immobilized enzyme were estimated as 20 and 16μmolglucose/(minμlenzyme), respectively. The newly developed method is simple yet effective and could be used for the immobilization of some other enzymes.
Keywords: Gelatin; Glucoamylase; Glutaraldehyde; Polyglutaraldehyde; Immobilization; Maltodextrin
Improving albumin production of hepatic lineage cells from mouse embryonic stem cells in vitro by Chih-Hsiu Yin; Wannhsin Chen; Chang-Chun Hsiao; Chao-Long Chen; Wen-Teng Wu (pp. 435-442).
Embryonic stem (ES) cells can differentiate into hepatic lineage cells in vitro and can potentially be used as source of hepatocytes in research and therapy. A good source of ES cell-derived hepatocytes with greater liver function may be needed when attempting to transplant hepatocytes or use bioartificial livers to treat liver disease. This in vitro study explores the use of mouse ES cells to derive hepatic lineage cells able to produce greater levels albumin. To do this we designed a series of experimental studies and developed a refined culture method which involved adjusting the composition of culture medium and the time that it would be used. The embryoid bodies (EBs) cultured by this method produced hepatic lineage cells capable of producing high amounts of albumin (1.90±0.198pg/hcell). These cells, which were able to uptake indocyanine green (ICG), expressed the hepatic genes α1-anti-trypsin (AAT), α-fetoprotein (AFP), albumin, carbamoyl-phosphate synthetase 1 (CPS1), cytochrome P450 7A1 (CYP7A1), glucose-6-phosphatase (G6P), tyrosine aminotransferase (TAT), tryptophan 2,3-dioxygenase (TDO2), and transthyretin (TTR). In conclusion, we found that this method allowed us to effectively derive high albumin-producing ES cell-derived hepatic lineage cells for experimental and clinical use.
Keywords: Embryonic stem cells; Hepatic differentiation; Dexamethasone; Albumin
Immobilization of specific antibody on SAM functionalized gold electrode for rabies virus detection by electrochemical impedance spectroscopy by Mouna Hnaien; Mohamed Fethi Diouani; Saloua Helali; Iméne Hafaid; Walid Mohamed Hassen; Nicole Jaffrezic Renault; A. Ghram; Adnane Abdelghani (pp. 443-449).
The rabies constitutes one of the most dangerous viruses causing many death cases every year. Each year approximately 55,000 people die of rabies, with high percentage of children. High percentages (99%) of the registered cases were in Asia and Africa. In order to fight this dangerous disease, many techniques are usually used for diagnostic but are usually complex, heavy, expensive, difficult to implement, requiring high-qualified personnel, and this is a necessity of developing new detection process. In this work, we describe the development of an immunological sensor based on functionalized gold electrode allowing rabies antigen detection. The biosensor is based on the immobilization of specific rabies antibodies onto functionalized gold microelectrode. The affinity interaction of the immobilized antibody with the specific antigen can be measured with low limit detection and with a good reproducibility with impedance spectroscopy. The non-specific interaction has been tested using the Newcastle antigen.
Keywords: Rabies virus; Immunoaffinity chromatography method; Gel electrophoresis; Immunosensor; Impedance spectroscopy
Production of ricinoleic acid estolide with free and immobilized lipase from Candida rugosa by A. Bódalo; J. Bastida; M.F. Máximo; M.C. Montiel; M. Gómez; M.D. Murcia (pp. 450-456).
Ricinoleic acid estolide was produced by using free and immobilized Candida rugosa lipase at moderate temperature in a bioreactor. This work describes the immobilization of C. rugosa lipase on 10 different supports by covalent binding and physical adsorption, and how of the most suitable immobilized derivative was selected. The comparison was mainly based on the enzyme content and on the activity results. An anion exchange resin was judged to be the most appropriate support and the corresponding immobilization process was investigated and optimized. Although repeated batch reactions using the same derivative are not entirely advisable, the reaction proceeds at a noticeably slower rate and the degree of condensation reached is lower when the same amount of protein as in the derivative is added to the bioreactor in native form.
Keywords: Estolide; Ricinoleic acid; Lipase; Immobilized enzymes; Heterogeneous biocatalysis
Kinetics of reactive azo-dye decolorization by Pseudomonas luteola in a biological activated carbon process by Yen-Hui Lin; Jyh-Yih Leu (pp. 457-467).
A laboratory-scale biological activated carbon (BAC) process was conducted to treat a reactive azo-dye (reactive red 22) by Pseudomonas luteola and the kinetics of azo-dye decolorization was investigated. The BAC-reactor removed 89% of reactive red 22 while P. luteola biofilm and suspended P. luteola reached a maximum growth rate at a steady-state condition. The azo-dye effluent from BAC-reactor met a discharge standard required by Taiwan government. The kinetic BAC-model, based on fundamental mechanisms, including surface diffusion, liquid-film mass transfer, Monod kinetics, growth of biofilm and suspended cells as well as shear loss of biofilm, was developed to describe the performance of biofilm attached on activated carbon in the azo-dye treatment process. The kinetic BAC-model predictions and experimental results for simultaneous adsorption and biodegradation of azo-dye contaminants were compared. It is shown that the fundamental mechanisms of BAC-process for azo-dye decolorization are not the simple addition but the synergetic combination of carbon adsorption and biodegradation of P. luteola strain. The major aspects of such synergism are the bioregeneration of the adsorbent and the reduction of the toxic effect of azo-dye contaminants in textile wastewater on P. luteola strain. The kinetic BAC-model not only provides insights into underlying mechanisms of adsorption and biodegradation but also can be used as a powerful tool to assist the design of a pilot-scale or full-scale BAC-process to treat azo-dye contaminants by P. luteola cells in textile wastewater.
Keywords: Reactive azo-dye; Decolorization; Pseudomonas luteola; BAC-process; Kinetic BAC-model
Biological hydrogen production from CO: Bioreactor performance by Ku Syahidah Ku Ismail; Ghasem Najafpour; Habibollah Younesi; Abdul Rahman Mohamed; Azlina Harun Kamaruddin (pp. 468-477).
This paper presents an alternative solution to the current problem faced by the world; diminishing of fossil fuel. Bioconversion of synthesis gas to hydrogen as clean fuel was catalyzed by a photosynthetic bacterium, Rhodospirillum rubrum. The clean fuel production was biologically mediated by the water–gas shift reaction in a 2l bioreactor. The work performed was on agitation effects on hydrogen production, KL a and power consumption. The results show that 500rpm was the suitable agitation rate to be employed. The hydrogen production was optimized at 0.44±0.023atm giving a KL a of 86.4±3.5h−1. The production rate was 9.6mmol H2/h. The maximum light conversion efficiency at agitation speed of 800rpm, light intensity of 500lux (732kW/m2) and 4g/l inlet acetate concentration was about 10.84±1.73%. At this condition, the maximum CO conversion efficiency was found to be 81±5.6%. The ratio of power per volume was calculated to be 322.30±12.14kW/m3 and foaming problem was successfully avoided. The corresponding power consumption was estimated to be about 0.64±0.03kW, while the output hydrogen energy was determined to be 643.2±26kW. A prolonged operation of continuous hydrogen production employing a microsparger showed stable behaviour for a duration of 27 days.
Keywords: Bioreactor; Hydrogen; Rhodospirillum rubrum; Synthesis gas; CO
Study on biosorption of humic acid by activated sludge by Hua-Jun Feng; Li-Fang Hu; Qaisar Mahmood; Yan Long; Dong-Sheng Shen (pp. 478-485).
The biosorption performance of humic acid (HA) by activated sludge and the effects of inorganic metal ions as biosorption aid were investigated. It was confirmed that biosorption instead of biodegradation was responsible for HA removal. HA biosorption by activated sludge followed the Freundlich isotherm equation; however, biosorption of HA corresponded to the biosorption by a mixture of adsorbates. The removal efficiency improved when initial HA concentration was increased. While biosorption of HA can be suitably applied to treat high concentration HA wastewater because the HA concentration of blank sample was approximate to 1mg/L. The total removal efficiency for HA improved when the quantity of adsorbent (activated sludge) was increased under constant contact time. The lower concentration of the adsorbent could realize the higher adsorptive capacity per gram activated sludge with a longer contact time, but the removal rate of pollutants was more important consideration in practice. Moreover, biosorption of HA was favored by addition of five metallic salts. The ionic strength increasing, cationic bridge, destabilization and precipitation are the main mechanisms to advance HA removal efficiency in solution after adding the salt (Na+), alkaline earth metallic (Ca2+, Mg2+) and hydrolyzing metallic (Al3+, Fe3+) ions, respectively.
Keywords: Activated sludge; Biosorption; Biodegradation; Biophysical chemistry; Humic acid; Wastewater treatment
Kinetic model for DBT desulphurization by resting whole cells of Pseudomonas putida CECT5279 by A. Alcon; A.B. Martin; V.E. Santos; E. Gomez; F. Garcia-Ochoa (pp. 486-495).
Bio-desulphurization kinetics of dibenzothiophene (DBT) using Pseudomonas putida CECT 5279, a genetically modified micro-organism (GMO), is studied. A kinetic model describing the 4S route of DBT desulphurization is proposed. Bio-desulphurization experiments have been carried out using resting whole cells of P. putida CECT 5279 obtained at different growth times as biocatalysts. The kinetic equations proposed for each reaction have been previously checked by studying each reaction of the 4S route individually, employing different substrates in different experiments. Finally, simple Michaelis–Menten kinetic equations for the three first reactions catalyzed by two mono-oxygenases (DszC and DszA) and a kinetic equation taking into account competitive inhibition due to product for the final reaction catalyzed by a desulfinase (DszB) have been adopted. DBT has been desulphurized using cells obtained at different growth times (5, 10, 23, 30 and 45h). The overall kinetic model proposed involving the four reactions of the 4S route was fitted to all the experimental data yielding a set of kinetic parameters able to describe the system evolution. Cell age has influence on the rates of all the reactions: reactions (1), (2) and (3) present maximum rates for cell grown during 30h, while reaction (4) shows a maximum rate for cells with around 10h of growth time. However, affinities of each substrate and the inhibition constant of the last reaction are not influenced by the time of growth.
Keywords: Kinetic modelling; Dibenzothiophene; 4S route; Pseudomonas putida; Biodesulphurization; Kinetic parameters; Growth; Product inhibition
Response surface optimization ofl-(+)-lactic acid production using corn steep liquor as an alternative nitrogen source by Lactobacillus rhamnosus CGMCC 1466 by Lei Yu; Ting Lei; Xiaodong Ren; Xiaolin Pei; Yan Feng (pp. 496-502).
Response surface methodology involving central composite design was successfully applied to evaluate the effect of corn steep liquor along with glucose, molasses, Tween80 and MnSO4 onl-(+)-lactic acid fermentation by Lactobacillus rhamnosus CGMCC 1466. Corn steep liquor was investigated as a sole and low cost nitrogen source in cooperation with other components to substitute yeast extract for the economical production ofl-(+)-lactic acid. Statistical analysis of the results showed that the linear and quadratic terms of these five variables had significant effects. The interactions between the five variables were found to contribute to the response at a significant level. A second-order polynomial regression model estimated that the maximum lactic acid production of 113.05g/l was obtained when the optimum concentrations of glucose, molasses, corn steep liquor, Tween80 and MnSO4 were 118.20g/l, 37.27ml/l, 42.54g/l, 1.52ml/l and 0.30g/l, respectively. Verification of the optimization showed thatl-(+)-lactic acid production of 115.12g/l was achieved in the shake-flask experiment, while the concentration of lactic acid in fermenter was 110.00g/l. However, the fermentation time using fermenter was shorter than the corresponding fermentation time obtained from the shake-flask cultivation by 12h. Comparing to the lactic acid production in the medium with yeast extract as the only nitrogen source, lactic acid production in the optimized medium was increased by 30.4%. Moreover, the yield and the average volumetric productivity of lactic acid were as high as 96% and 4.58g/lh, respectively.
Keywords: l; -(+)-Lactic acid; Lactobacillus rhamnosus; Corn steep liquor; Response surface methodology; Medium optimization; Nitrogen source
Adsorption mechanism for imprinted ion (Ni2+) of the surface molecular imprinting adsorbent (SMIA) by Haijia Su; Jia Li; Tianwei Tan (pp. 503-509).
The adsorption mechanism for the imprinted ion (Ni2+) of a novel surface molecular imprinting adsorbent (SMIA) prepared by the imprinting technique was studied. The interaction mechanism for the imprinted ion (Ni2+) with –OH and –NH2 groups on the chitosan molecules was testified by Fourier transform-infrared spectrometry (FT-IR) and X-ray photoelectron spectroscopy (XPS). By the means of FT-IR and XPS analysis, there exist two kinds of –NH2 groups on the chitosan molecule. Most –NH2 groups showed higher adsorption activity owing to using the imprinting technique in the adsorbent preparation, whereas a few –NH2 groups displayed a lower adsorption activity because of being cross-linked in preparation, which caused different adsorption mechanisms for Ni2+. Compared with the surface molecular non-imprinting adsorbent (non-SMIA), both –OH and –NH2 groups on the imprinted adsorbent surface could provide higher adsorption activity to Ni2+ based on FT-IR and XPS analyses. SMIA had more pores and bigger specific surface area than non-SMIA according to the distribution of the pore diameter and specific surface area analyses. Based on the above research, a higher adsorption capacity and a better selectivity for the imprinted ions of SMIA could be interpreted.
Keywords: Adsorption mechanism; Metal ion; The surface molecular imprinting adsorbent (SMIA); Fourier transform-infrared spectrometry; X-ray photoelectron spectroscopy
Production and single step purification of cyclodextrin glycosyltransferase from alkalophilic Bacillus firmus by ion exchange chromatography by Laxman S. Savergave; Santosh S. Dhule; Vitthal V. Jogdand; Sanjay N. Nene; Ramchandra V. Gadre (pp. 510-515).
Production and purification of starch digesting cyclodextrin glycosyl transferase (CGTase) from alkalophilic Bacillus firmus was investigated. Fermentation was carried out in 14l bioreactor at 28°C using a medium containing dextrin, yeast extract, peptone, (NH4)H2PO4 and MgSO4·7H2O. The extracellular enzyme was concentrated by tangential flow ultrafiltration. The concentrated enzyme was chromatographed using DEAE-sepharose and phenyl sepharose. DEAE-sepharose could be used to purify CGTase in a single step with 23.1 fold purification and 80.6% recovery. The enzyme obtained had homogeneity and the molecular weight was 76kDa confirmed by SDS-PAGE.
Keywords: CGTase; Bacillus firmus; Cyclodextrin; Alkalophilic; Purification
Kinetic study on the hydrolysis of palm olein using immobilized lipase by Yin Hoon Chew; Lee Suan Chua; Kian Kai Cheng; Mohamad Roji Sarmidi; Ramlan Abdul Aziz; Chew Tin Lee (pp. 516-520).
The application of immobilized lipase (EC 3.1.1.3) is gaining interest in the oleochemical industry as it offers advantages over conventional chemical reactions. In the present study, a commercial immobilized lipase, Lipozyme TL IM, was used to catalyze the hydrolysis of palm olein in an aqueous-organic phase. A ping-pong bi-bi model with substrate inhibition by water was used to describe the hydrolysis reaction. The reaction rate constants of the proposed mechanism were determined by fitting the model into experimental data using a nonlinear curve fitting software. Based on the results of this study, the model proposed was able to fit the data with a correlation coefficient of 0.9586. The rate of formation of fatty acids is limited by the formation of glycerol. The critical water content before inhibition occurs was found to be 3.6% (v/v). No inhibition by palm olein was observed up to a concentration of 874.76g/l.
Keywords: Aqueous two phase; Immobilized enzymes; Lipase; Heterogeneous reactions; Modeling; Hydrolysis
Adsorption of copper on rubber ( Hevea brasiliensis) leaf powder: Kinetic, equilibrium and thermodynamic studies by W.S. Wan Ngah; M.A.K.M. Hanafiah (pp. 521-530).
The adsorption of Cu(II) ions from aqueous solution by rubber ( Hevea brasiliensis) leaf powder (RHBL) was studied in a batch adsorption system. Characteristics of RHBL such as pH of aqueous slurry, pH of zero point charge (pHZPC), surface area and pore diameter, Fourier transform infrared (FTIR), scanning electron microscopy (SEM) and electron dispersive spectroscopy (EDS) were investigated. Factors influencing adsorption such as pH of the solution, adsorbent dosage, particle size, copper concentration and temperature have been studied. The adsorption process was relatively fast and equilibrium was achieved after about 60min. Maximum adsorption of Cu(II) ions occurred at around pH 4–5. The kinetic data were analyzed using various kinetic models particularly pseudo-first-order, pseudo-second-order, Ritchie's-second-order and intraparticle diffusion. The pseudo-second-order kinetic model was found to agree well with the experimental data. Adsorption equilibrium data could also be described well by Langmuir, Freundlich and Dubinin–Radushkevich isotherm models. Based on the Langmuir isotherm, the monolayer adsorption capacity of Cu(II) ions was 8.92mgg−1. Thermodynamic parameters such as enthalpy change (Δ H°), free energy change (Δ G°) and entropy change (Δ S°) were calculated and adsorption process was spontaneous and exothermic. Copper removal by RHBL involved different kinds of mechanisms such as ion-exchange, complexation and physisorption.
Keywords: Adsorption; Copper; Rubber leaf powder; Kinetic; Isotherms; Thermodynamic
Immobilization of a recombinant thermostable esterase ( Pf2001) from Pyrococcus furiosus on microporous polypropylene: Isotherms, hyperactivation and purification by Rodrigo Volcan Almeida; Roberta Vieira Branco; Bruno Peixoto; Cíntia da Silva Lima; Sylvia Maria Campbell Alqueres; Orlando Bonifácio Martins; Octavio Augusto Ceva Antunes; Denise Maria Guimarães Freire (pp. 531-537).
In this study, a recombinant thermostable esterase ( Pf2001Δ 60) from the hyperthermophilic archaea Pyrococcus furiosus was immobilized on microporous polypropylene (Accurel MP 1000). The adsorption was rapid, with 90% total protein and esterase activity being retained in the first 15min. No desorption of the enzyme was detected in a time course of 180min after immobilization, which indicates an intense enzyme–support interaction. The adsorption isotherms from the raw protein extract were determined by total protein quantification and esterase activity in the adsorption medium. Two distinct behaviors were observed: For total protein, the experimental data adjusted well to the Langmuir model ( qm=35.3mgg−1 and Ka=16.1mLmg−1), indicating the formation of a monolayer; while the experimental data for esterase activity correlated better with the multilayer Langmuir model ( qm=4.4U/g, Ka=2223.7mLU−1 and Kaa=25.7mLU−1), indicating the possible formation of a bilayer. Effect of enzyme immobilization on activity (hyperactivation) was evaluated by retention activity parameter ( R%). This parameter was dependent of the protein/support ratio at the beginning of the immobilization process. Two hundred and thirty-seven percent hyperactivation was observed when the protein/support ratio was 18mg/g protein. Furthermore, the immobilization process by means of selective adsorption permitted the purification of the esterase from P. furiosus in a single step.
Keywords: Esterase immobilization; Accurel; Pyrococcus furiosus; Hyperactivation; Purification
Removal of malachite green (MG) from aqueous solutions by native and heat-treated anaerobic granular sludge by Wen Cheng; Shu-Guang Wang; Lei Lu; Wen-Xin Gong; Xian-Wei Liu; Bao-Yu Gao; Hua-Yong Zhang (pp. 538-546).
The performance of native and heat-treated anaerobic granular sludge in removing of malachite green (MG) from aqueous solution was investigated with different conditions, such as pH, ionic strength, initial concentration and temperature. The maximum biosorption was both observed at pH 5.0 on the native and heat-treated anaerobic granular sludge. The ionic strength had negative effect on MG removal. Kinetic studies showed that the biosorption process followed pseudo-second-order and qe for native and heat-treated anaerobic granular sludge is 61.73 and 59.17mg/g at initial concentration 150mg/L, respectively. Intraparticle diffusion model could well illuminate adsorption process and faster adsorption rate of native anaerobic granular sludge than heat-treated anaerobic granular sludge. The equilibrium data were analyzed using Langmuir and Freundlich model, and well fitted Langmuir model. The negative values of Δ G° and Δ H° suggested that the interaction of MG adsorbed by native and heat-treated anaerobic granular sludge was spontaneous and exothermic. Desorption studies revealed that MG could be well removed from anaerobic granular sludge by 1% (v/v) of HCl–alcohol solution.
Keywords: Biosorption; Malachite green; Anaerobic granular sludge; Heat-treatment; Kinetics
Kinetics of distillation of essential oil from comminuted ripe juniper ( Juniperus communis L.) berries by Svetomir Ž. Milojević; Tamara D. Stojanović; Radosav Palić; Miodrag L. Lazić; Vlada B. Veljković (pp. 547-553).
The distillation of essential oil from comminuted ripe berries of Juniperus communis L. (juniper oil) was studied at different hydrodistillation rates. The distillation of juniper consisted of an initial, fast oil distillation followed by a slow oil distillation. Based on this mechanism, the kinetics of juniper oil distillation were described using a two-parameter model of unsteady-state diffusion through the plant material. The hydrodistillation rate and berries-to-water ratio were shown to affect the distillation rate, process duration, yield, composition and physical properties of the juniper oil. Both the fast distillation rate and the yield of juniper oil increased with increasing hydrodistillation rate. The fast oil distillation rate increased and the oil yield decreased somewhat with increasing berries-to-water ratio. The amount of alpha-pinene decreased and the amount of myrcene increased with increasing hydrodistillation rate.
Keywords: Essential oil; Hydrodistillation; Juniperus communis; L.; Juniper; Juniper berries; Juniper oil
Using a wall-driven flow to reduce the external mass-transfer resistance of a bio-reaction system by Mohammad Al-Shannag; Zakaria Al-Qodah; Joan Herrero; Joseph A.C. Humphrey; Francesc Giralt (pp. 554-565).
The two-dimensional momentum and mass transfer in an immobilized enzyme reactor was numerically investigated. The equations of motion and the mass-transport equation of a substrate, consumed at specified boundaries of the reactor, were solved by using fourth-order discretization schemes. A wall-driven cavity of square cross-section was selected to study the convective transport contributions to the movement of substrate from the bulk solution to an immobilized enzyme surface. The numerical results provided field distributions of the local velocity and substrate concentration as a function of external-mass transfer rates and reaction limitations. The flow field structure of the system under consideration facilitated the interpretation of the effect of hydrodynamic conditions on transport processes and reactor performance was evaluated from the effectiveness factor obtained at different operating conditions. The influence of the operational Peclet number ( Pe≤1000) on reactor performance was obtained for different values of the Reynolds number ( Re≤700). Results indicated whether mass transport was limited by reaction or by external mass-transfer resistances; the effects of high enzyme activity on operating conditions were also established.
Keywords: Wall-driven cavity; Mass transfer enhancement; Immobilized-enzyme reactor; Effectiveness factor; Effective diffusion; Bioreactors
Unstructured generalized models for the analysis of the inhibitory and the nutritional limitation effects on Lactobacillus helveticus growth—Models validation by Abdellah Bouguettoucha; Béatrice Balannec; Abdeltif Amrane (pp. 566-574).
During lactic acid fermentation, an inhibitory effect was recorded during seed cultures, usually carried out without pH control; while nutritional limitations (nitrogen) were observed during cultures, carried out at pH controlled at 5.9, which ceased when carbon became limiting. To avoid the use of two different expressions, depending on culture conditions, a generalized model for production was developed, involving a unique expression taking into account both a nutritional limitation and an inhibitory effect. In some conditions, namely at acidic pH control, the model failed to describe accurately growth- and non-growth-associated production. Therefore, the inhibitory term related to the undissociated lactic acid inhibition was added in the growth relation (modified Verlhust model), instead of the production model. The modified Verlhust model allowed a dissociation of the inhibitory and the nutritional effects. A modified Luedeking-Piret expression, involving a carbon substrate limitation to account for cessation of production was considered for the production model. This model proved to satisfactory describes growth and production data in the wide range of culture conditions examined; it also allowed a fine identification and characterization of growth and production parameters.
Keywords: Batch processing; Kinetic parameters; Lactic acid; Product inhibition; Modelling; Substrate limitation
High efficiency production of astaxanthin by autotrophic cultivation of Haematococcus pluvialis in a bubble column photobioreactor by Reza Ranjbar; Ryota Inoue; Hironori Shiraishi; Tomohisa Katsuda; Shigeo Katoh (pp. 575-580).
Haematococcus pluvialis was cultivated under photoautotrophic conditions in a bubble column with fed-batch addition of nutrients, especially nitrate, and a cell number above 5×106cellsmL−1 was attained after 300h.The reduction of nutrient concentrations accompanied by dilution of the fermentation broth and an increase in the light intensity enhanced accumulation of astaxanthin. The final astaxanthin concentration of 390mgL−1 was several times higher than ever reported. This combination of fed-batch addition of nutrients and dilution of broth for nutrient deficiency is a promising method for attainment of high cell and astaxanthin concentrations in a bubble column photobioreactor.
Keywords: Haematococcus pluvialis; Autotrophic culture; Bubble column; Fed-batch; Nitrate concentration; Astaxanthin
Quantification of a specific bacterial strain in an anaerobic mixed culture for biohydrogen production by the aerobic fluorescence recovery (AFR) technique by Chong Zhang; Xin-Hui Xing (pp. 581-585).
To analyze a mixed culture consisting of gfp-harbored Enterobacter aerogenes and Clostridium paraputrificum for hydrogen production, a method by an aerobic fluorescence recovery (AFR) of GFP expressed under anaerobic conditions has been studied. The concentrations of the respective strain in the mixed culture were calculated based on the fluorescence after AFR. E. aerogenes grew in the early stages because of its insensitivity to the residual oxygen in the medium. C. paraputrificum became the dominant strain in the cultivation period after the consumption of oxygen. According to the repartition of the two strains in the mixed culture and the hydrogen production profile of the respective pure cultures, the hydrogen production by the mixed culture could be calculated.
Keywords: Anaerobic processes; Bioprocess monitoring; Microbial growth; Fermentation; Biohydrogen; GFP
Assessment of the stability of TGFβ3 bioactivity for potential bioreactor applications by D. Vonwil; D. Wendt; S. Ströbel; H.J. Wallny; D. Gygax; M. Heberer; I. Martin (pp. 586-589).
In order to develop suitable bioreactor systems and processes for automated and standardized cell cultures involving the use of bioactive factors, we determined the stability of transforming growth factor beta 3 (TGFβ3) over storage time and under conditions typically used for mammalian cell culture. Using a reporter gene assay with firefly luciferase as readout, significant reduction of TGFβ3 bioactivity was detected to occur both in serum containing medium (SCM) and serum free medium (SFM). The residual activity, quantified by parallel line assays, progressively decreased with time, down to 60% in SCM and 84% in SFM after 1 week at 37°C, with no further decrease until 3 weeks, whereas such loss could not be predicted using a conventional ELISA method. The reduction of TGFβ3 bioactivity had a negligible influence in a typical biological assay (e.g., chondrocyte proliferation), supporting the possibility of prolonged storage of medium pre-supplemented with TGFβ3 for bioreactor-based chondrocyte expansion. With the ultimate goal of defining suitable operating protocols for automated cell culture bioreactors, the proposed approach should be extended to assessing the stability of other possibly labile medium supplements.
Keywords: Growth factor; Tissue engineering; Bioassay; Automation; Standardization; Bioprocess
A mechanism for internal reflux in foam fractionation by Paul Stevenson; Xueliang Li; Geoffrey M. Evans (pp. 590-593).
Multiple equilibrium stages can be engendered in foam fractionation, a process used for the enrichment of streams of proteins, by returning some of the foamate stream to the top of the column as external reflux liquor. However, it was recognised, 40 years ago that reflux could be autogenously created through the coalescence of bubbles in fractionation columns. By invoking the hydrodynamic theory of rising foam, we suggest a mechanism for the creation of internal reflux in foam fractionation. This method can give internal reflux rate as a function of bubble size. However, since the bubble size profile in a rising foam cannot be estimated, we cannot yet estimate how internal reflux varies with position in the column.
Keywords: Foam fractionation; Enrichment; Reflux; Foam
An aseptically operatable static solid state bioreactor consisting of two units by Veera Virtanen; Antti Nyyssölä; Matti Leisola; Pekka Seiskari (pp. 594-597).
A novel, aseptic 100l packed bed bioreactor consisting of two vessels was developed and tested. One vessel was used for substrate sterilization and the other for cultivation. The sterilized medium was transported by vibration to the cultivation vessel. Even distribution of the inoculum throughout the substrate was achieved by spraying the inoculum on the medium during its transport to the cultivation vessel. Two different mycelial microorganisms were cultivated in the bioreactor: the fungus Phlebiopsis gigantea and the bacterium Streptomyces sp. K61 which are used commercially as biofungicides. The bioreactor was easy to use and the temperature was maintained at an acceptable level. The final spore concentrations obtained in the cultivations were 3.6×106cfu/g for P. gigantea and 4.5×109cfu/g for Streptomyces sp. in the dried media.
Keywords: Batch processing; Biofungicides; Microbial growth; Packed bed bioreactor; Scale-up; Solid state fermentation
Succession of bacterial community and enzymatic activities of activated sludge by heat-treatment for reduction of excess sludge by Sangtian Yan; Kazuhiko Miyanaga; Xin-Hui Xing; Yasunori Tanji (pp. 598-603).
Heat-treatment has been used for the reduction of excess sludge as a simple process. To clarify the relationship between reduction efficiency and biological response of sludge matrix during heat-treatment, microbial population and hydrolytic enzyme (protease) activity of a municipal activated sludge were studied. Culture-dependent analysis showed the rapid increase in the population of thermophilic bacteria at the early stage of heat-treatment and the emergence of protease-secreting bacteria. Culture-independent analysis by denaturing gradient gel electrophoresis (DGGE) revealed that the Bacilli, which include most of thermophiles, became the dominant class in the community by the treatment. The protease activity in supernatant of the sludge increased instantly after 1h heat-treatment, which was considered to be released from microbial cells by lysis. The protease activity succession was correlated with the microbial succession and also with the change in MLSS and TOC concentrations during heat-treatment, suggesting that the protease activity plays an important role in the lysis-cryptic growth induced by heat-treatment.
Keywords: Sludge reduction; Lysis-cryptic growth; Bacterial community; Protease; DGGE
Ethanol production from kitchen garbage using response surface methodology by Qunhui Wang; Hongzhi Ma; Wenlong Xu; Lijuan Gong; Wenyu Zhang; Dexun Zou (pp. 604-610).
Response surface methodology based on central composite design (CCD) was utilized to optimize the conditions of simultaneous saccharification and fermentation (SSF) for ethanol production from kitchen garbage. Both open and close fermentation were carried out in this study to test their effects on ethanol production. In this study, the result showed that open fermentation without undergoing heat treatment was better due to the unspoiled nutrients inside. Maximum ethanol concentration of 33.05g/L was obtained with the optimum conditions of time of 67.60h, pH of 4.18 and temperature of 35°C. Second order polynomial models were developed to quantify the relationships between variables. It showed that linear effect of pH, cross-effect between time and pH, square effects of time and pH showed trivial influence on ethanol production. The result of conformation experiment under the optimum conditions agreed well with the model predictions (34.21 with 33.05). The ethanol yield could reach 0.23g ethanol per dry gram garbage, which showed the technology could be an ideal method to utilize kitchen garbage. Ethanol production from kitchen garbage by open fermentation could to a large extent save the cost and eliminate threats of solid-waste.
Keywords: Kitchen garbage; Ethanol; Response surface methodology; Optimization