Ultrafiltration membrane enzymatic reactors,polarized versus stirred reactor performance

Conclusions The use of polarized U.F. membrane enzymatic reactors yields considerable stabilization of the enzyme activity because of the high concentration levels attained by the protein in the polarization layer.Further enzyme stabilization is achieved when even higher overall concentrations are attained by injecting an inert, linear-chain polymer into the system.Both effects are a direct consequence of the polarization phenomena that take place in an unstirred system and hence disappear when dealing with a stirred cell.No appreciable reduction in initial enzyme activity level occurs in the polarized system as compared to the soluble enzyme situation.     

Technical aspects of separation and simultaneous enzymatic reaction in multiphase enzyme membrane reactors

The technical aspects of the membrane extraction of a compound either from aqueous phase into apolar organic solvent phase or from the apolar phase to the aqueous one and the enzymatic conversion of the solute in a multiphase enzyme membrane reactor are considered. The application possibilities, the selection aspects of membrane material as well as the solvent phase, the water content and its control, the method of the enzyme immobilisation and the operation of the extraction/reaction system are discussed.     

Ultrafiltration membrane reactors for enzymatic resolution of amino acids: design model and optimization

In this paper the possibility of continuous resolution of DL-phenylalanine, catalyzed by L-aminoacylase in a ultrafiltration membrane reactor (UFMR) is presented. A simple design model, based on previous kinetic studies, has been demonstrated to be capable of describing the behavior of the experimental system. The model has been used to determine the optimal experimental conditions to carry out the asymmetrical hydrolysis of N-acetyl-DL-phenylalanine.     

Three different coupled enzymatic systems for in situ regeneration of NADPH

Three different coupled enzymatic systems used in the reduction of sulcatone by alcohol dehydrogenase from Thermoanaerobium brockii (TBADH), were kinetically compared. The first one involved the use of TBADH for both the principal and recycling reactions and 2-propanol 20%, v/v as the recycling substrate. The other two were based on the use of a different enzyme, glucose- or glucose-6-phosphate dehydrogenases, for in situ regeneration of NADPH. The coupled-substrate approach achieved 100% of conversion against 84% of the other two systems.     

A study on enzymatic reaction using a liquid emulsion membrane technique

An enzymatic reaction using a liquid emulsion membrane technique was studied to investigate the effects of some experimental variables on the stability of liquid membrane, enzyme deactivation, and transport of substrates and products. The hydrolysis of L-phenylalanine methyl ester by alpha-chymotrypsin was selected as a model reaction system. First, a transport mechanism for the substrates and products across the membrane was qualitatively identified. Second, it was found that the pH of the internal phase was one of the most important variables to determine the enzyme activity in a liquid membrane. Third, the effect of membrane phase which consists of surfactant, carrier, and organic solvent on the emulsion stability was investigated. It was found that the properties of the organic solvents greatly affect the emulsion stability. For an optimum condition, it was possible to reuse the emulsion which consists of membrane phase and internal phase without further separation. It was finally concluded that the enzyme in a liquid membrane retained 60% of its native activity in spite of vigorous mixing during the emulsification step.     

Performance evaluation of reactors designed for bioconversion of wheat straw to animal feed

A chronology of reactor design from laboratory scale to pilot scale for the bioconversion of wheat straw to animal feed is presented. The engineering criteria considered at each stage of development are discussed. Designs were executed at each stage and their performance was compared based on engineering and bioconversion parameters. Illustrative detailed analyses of data obtained from performance evaluation experiments from selected designs are provided. Schematics diagrams of the different generations of reactor designs are also presented.     

Biofilm reactors for industrial bioconversion processes: employing potential of enhanced reaction rates

This article describes the use of biofilm reactors for the production of various chemicals by fermentation and wastewater treatment. Biofilm formation is a natural process where microbial cells attach to the support (adsorbent) or form flocs/aggregates (also called granules) without use of chemicals and form thick layers of cells known as "biofilms." As a result of biofilm formation, cell densities in the reactor increase and cell concentrations as high as 74 gL^-1 can be achieved. The reactor configurations can be as simple as a batch reactor, continuous stirred tank reactor (CSTR), packed bed reactor (PBR), fluidized bed reactor (FBR), airlift reactor (ALR), upflow anaerobic sludge blanket (UASB) reactor, or any other suitable configuration. In UASB granular biofilm particles are used. This article demonstrates that reactor productivities in these reactors have been superior to any other reactor types. This article describes production of ethanol, butanol, lactic acid, acetic acid/vinegar, succinic acid, and fumaric acid in addition to wastewater treatment in the biofilm reactors. As the title suggests, biofilm reactors have high potential to be employed in biotechnology/bioconversion industry for viable economic reasons. In this article, various reactor types have been compared for the above bioconversion processes.     

Enzymatic saccharification of cellulose in membrane reactors

The kinetics of enzymatic saccharification of ball-milled sugar-cane bagasse, sorghum stubble and peanut shells was studied and their conversions compared. Particle size analyses were performed on the bagasse sample and pure cellulose (Solka-Floc). It was revealed that most of the size reduction of cellulose particle took place between 0 5% conversion. Means of using commercially available ultrafiltration units as continuous-flow membrane reactors to reduce glucose inhibition were tested and compared using Solka-Floc as substrate. It was pointed out that a low conversion CSTR placed between a ball-mill and a hollow-fibre cartridge could reduce the cost of pretreatment and prevent possible blockage of hollow fibres.     

Sitosterol bioconversion with resting cells in liquid polymer based systems

The use of a biocompatible water-immiscible organic phase as a substrate and product pool has been acknowledged as an effective tool to overcome the low volumetric productivity of aqueous bioconversion systems involving hydrophobic compounds. The growing environmental and public health awareness is nevertheless leading to restrictions in the use of organic solvents in industrial processes, in order to render these more environmentally friendly. Different approaches are hence being assessed for the design of alternative bioconversion media, involving the use of supercritical fluids, ionic liquids and natural oils and liquid polymers, among others.     

Direct bioconversion of alkali-pretreated straw using simultanesous enzymatic hydrolysis and acetone-butanol fermentation

Summary Conversion of alkali-pretreated wheat straw into butanol and acetone by Clostridium acetobutylicum has been achieved in a one-step hydrolysis and fermentation process involving the use of cellulase from Trichoderma reesei. In the conditions adopted, the results obtained for solvent concentration (17.3 g.l^-1) solvent yield (18.3% with respect to pretreated wheat straw) and overall conversion time (36 h) demonstrate an improved performance over the separate hydrolysis and fermentation operation.     

Managing microbial communities in membrane biofilm reactors

Membrane biofilm reactors (MBfRs) deliver gaseous substrates to biofilms that develop on the outside of gas-transfer membranes. When an MBfR delivers electron donors hydrogen (H₂) or methane (CH₄), a wide range of oxidized contaminants can be reduced as electron acceptors, e.g., nitrate, perchlorate, selenate, and trichloroethene. When O₂ is delivered as an electron acceptor, reduced contaminants can be oxidized, e.g., benzene, toluene, and surfactants. The MBfR’s biofilm often harbors a complex microbial community; failure to control the growth of undesirable microorganisms can result in poor performance. Fortunately, the community’s structure and function can be managed using a set of design and operation features as follows: gas pressure, membrane type, and surface loadings. Proper selection of these features ensures that the best microbial community is selected and sustained. Successful design and operation of an MBfR depends on a holistic understanding of the microbial community’s structure and function. This involves integrating performance data with omics results, such as with stoichiometric and kinetic modeling.

     

Three examples of anti-Fy3 produced in Negroes

We present three examples of anti-Fy3 produced by Negroes. Results of serologic studies were similar to those of previously reported examples of Negro produced anti-Fy3, including negative to weak reactivity with cord red blood cells, separable anti-Fya, and the presence of multiple unexpected alloantibodies. These findings reinforce the difference between anti-Fy3 produced by Negroes and that produced by non-Negroes. The rare formation of Duffy antibodies by Negroes may signify the presence of an amorphic gene at the Duffy locus.     

Preparation of vanillin by bioconversion in a silicon rubber membrane bioreactor

In this study, the bioconversion of clove oil into vanillin using soybean lipoxygenase (SBLOX) as biocatalyst was investigated in a silicon rubber membrane bioreactor (SRMBR) and shaking flasks. High performance liquid chromatography (HPLC) analysis indicated that the vanillin concentration was 8.14 mg/L after 36 h of conversion in a shaking flask. It reached up to 121.53 mg/L in the receiving solution after 36 h of conversion in the SRMBR. The conversion rate of clove oil was 0.033% in the shaking flask. It was 1.01% in the SRMBR. The peak area ratio of vanillin in the receiving solution of the SRMBR was 70.08%. By adding activated carbon into the conversion broth of the SRMBR, the vanillin concentration in the receiving solution reached 140.27 mg/L, the conversion rate of clove oil increased to 1.14%, and the peak area ratio of vanillin in the receiving solution reached 93.53%.     

Continuous enzymatic production and adsorption of laminaribiose in packed bed reactors

Bienzymatic production of laminaribiose from sucrose and glucose was combined with adsorption on zeolite BEA to introduce a first capture and purification step. Downstream processing including washing and desorption steps was characterized and optimized on a milliliter scale in batch mode. Results were then transferred to a packed bed system for enzymatic production and adsorption where the influence of adsorbent particle diameter on purity and productivity was evaluated. Finally, a continuous enzymatic production of laminaribiose was conducted over 10 days. The subsequent downstream processing of the loaded zeolites led to purities of over 0.5 g_{Laminaribiose} g_sugar^?1 in the desorbate with a total productivity of 5.6 mg_{Laminaribiose} L_{enzyme bed}^?1 h^?1 without the use of recycles.     

Continuous production of isovaleraldehyde through extractive bioconversion in a hollow-fiber membrane bioreactor

A membrane bioreactor was developed to perform an extractive bioconversion aimed at the production of isovaleraldehyde by isoamyl alcohol oxidation with whole cells of Gluconobacter oxydans. A liquid/liquid extractive system using isooctane as extractant and assisted by a hollow-fiber hydrophobic membrane was chosen to recover the product. The aqueous bioconversion phase and the organic phase were maintained apart with the aid of the membrane. The extraction of alcohol and aldehyde was evaluated by performing equilibrium and mass transfer kinetic studies. The bioprocess was then performed in a continuous mode with addition of the substrate to the aqueous phase. Fresh solvent was added to the organic phase and exhausted solvent was removed at the same flow rate. The extractive system enabled a fast and selective in situ removal of the aldehyde from the water to the organic phase. High conversions (72–90%) and overall productivity (2.0–3.0 g l⁻¹ h⁻¹) were obtained in continuous experiments performed with different rates of alcohol addition (1.5–3.5 g l⁻¹ h⁻¹). Cell deactivation was observed after 10–12 h of operation.     

Kinetics of multilayer immobilized enzyme-filter reactors: Behavior of urease-filter reactors in different buffers

A sequential model which describes the kinetic behavior of multilayer immobilized-enzyme filter reactors for systems obeying the Michaelis-Menten scheme and various types of inhibition by product and by substrate is proposed. The model was varified experimentaly using a single enzyme-filter-substrate system-urease bound to nylon-filter disks acting on urea-in different buffers to obtain the various inhibition patterns.     

Scale-up of flat-plate reactors for enzymatic hydrolysis of fats and oils

To determine the feasibility of continuous enzymatic fat-splitting, immobilized lipase reactors were constructed from alternating layers of enzyme support material and separator screens. Partially purified lipase from Thermomyces lanuginosus was loaded onto the support material at pH 5.5 by irreversible adsorption. Melted edible tallow at 51°C was pumped through the immobilized enzyme layers and swept from the downstream separator screens by buffer recycled from a continuous oil/water separator. Results from continuous operation of 10-layer reactors were compared with data from single-layer reactors. The activity per square centimeter of 10-layer reactors was nearly as much as that of single-layer reactors at the same enzyme loading and oil feed rate. Data were fitted to an empirical mathematical model.     

Resistance of Lactobacillus casei in plastic-composite-support biofilm reactors during liquid membrane extraction and optimization of the lactic acid extraction system

Lactic acid fermentations were performed with plastic-composite-support (PCS) disks in solvent-saturated media with Lactobacillus casei subsp. rhamnosus (ATCC 11443). The PCS disks contained 50% (w/w) polypropylene, 35% (w/w) ground soybean hulls, 5% (w/w) yeast extract, 5% (w/w) soybean flour, and 5% (w/w) bovine albumin. Bioassays were performed by growing L. casei in solvent-saturated media after soaking the PCS disks. Eighteen different solvent and carrier combinations were evaluated. Overall, L. casei biofilm fermentation demonstrated the same lactic acid production in solvent-saturated medium as suspended cells in medium without solvents (control). To evaluate PCS solvent-detoxifying properties, two bioassays were developed. When solvent-saturated medium in consecutive equal volumes (10 mL then 10 mL) was exposed to PCS, both media demonstrated lactic acid fermentation equal to the control. However, when solvent-saturated medium with two consecutive unequal volumes (10 mL then 90 mL) was exposed to PCS, some degree of toxicity was observed. Furthermore, iso-octane, tributylphosphate (TBP), and Span 80 were optimized for recovery as 91%, 5%, and 4% (v/v), respectively, with a 1:1 ratio of 1.2 M Na(2)CO(3) stripping solution. Also, recovery by emulsion liquid extraction in the hollow-fiber contactor was minimal due to low recovery at pH 5.0 and incompatibility of the solvent and hollow-fiber material. These results suggest that PCS biofilm reactors can benefit lactic acid fermentation by eliminating the toxic effect from solvent leakage into the fermentation medium from liquid-liquid extractive integrated fermentations.     

Characterisation of liquid and gas flow in jet loop reactors

The fluid dynamics in jet loop fermenters has been subject to experimental and theoretical investigation. It is demonstrated that by determination of Euler number, Bodenstein number, and residence time distribution for the gas phase it is possible to perform a reliable characterization of the fermenters. It can be shown that the investigated jet loop fermenters with internal loop closely resemble ideally mixed tanks.