Nonideal Flow Conditions In Bioreactors And Backmixing

Figure 10.7 Stimulus response technique. Figure 10.7 Stimulus response technique. fact, would have no distribution at all. The residence time distribution has the consequence of different conversions in different fractions of the exit stream usually with an average conversion between those obtained with ideal plug flow and completely mixed flow. The extent of residence time distribution can be decided by stimulus-response technique using a tracer, which can be injected into the reactor and then...

Heat Transfer

Heat is added or removed in a biological process to 1. Sterilize liquid reactor feed in a batch kettle. 2. Add heat to increase rate of reaction. For example, since heat generated in anaerobic sludge digestion is insufficient, heat needs to be added. 3. Remove excess heat produced during reaction to prevent denatura-tion of cells and proteins. For example, heat produced during hydrocarbon oxidation is 200 kcal, while during carbohydrate oxidation it is 80 kcal. 4. Dry cell sludge to remove...

Properties of Medium

The physical properties of the substrate and products produced also have an influence on the selection of reactor. For example, if methane is produced excessively during the reaction, then reactors with large interconnected gas volumes should not be used, since methane air form an explosive mixture. In the case of volatile substrates, cocurrent flow with little axial mixing or multistage units should be used in order to minimize losses in the waste gases. Higher paraffin has a reducing effect...

Rational Design Of Enzymes

And selectivity from a designed sequence of amino acids. 2. Synthesize nonprotein enzyme models (biomimics) with altered required activity. 4. Site-selective modification of existing proteins. Our understanding of the dynamics involved in the folding of protein molecules is not complete, despite a significant amount of work directed toward the correlation of primary structure (sequence of amino acids) with the three-dimensional structure. Therefore, it is not yet possible to construct a protein...

Dialysis

Separation in dialysis is due to concentration gradient and is used for the separation of small solutes from large synthetic or biological macromolecules. The membrane material retains larger molecules due to steric reasons, while the smaller solutes freely diffuse through the membranes, eventually leveling out concentration differences. If the osmotic pressure is different between the two phases, solvent molecules will also diffuse through the membrane, to reach equilibrium. Dialysis is used...

Biomass Phase External Surface

Ks as(C Cs) rate of consumption of oxygen Figure 12.3 Model for tower bioreactor. Figure 12.3 Model for tower bioreactor. The rate term in the oxygen balance depends additionally on the local concentrations of the carbon source and the biomass, and corresponding balances for them have to be formulated. In the case of biomass, sedimentation may also have to be taken into consideration, which gives where R is biomass generation term and us is the settling velocity of the biomass particles in the...

Super Secondary Structure

Simple combinations of a few secondary structure elements with a specific geometric arrangement have been found to occur frequently in protein structures. These units have been called either supersecondary structures or motifs. Some of these motifs can be associated with a particular biological function. Some of the common motifs with their biological function are Helix-loop-helix motif calcium binding Hairpin b-motif no specific function Helix-turn-helix motif DNA binding b-a-b-Motif no...

B

Figure 3.13 Free-energy change during a chemical reaction (a) via the formation of transition state, (b) effect of catalyst. activity. The dissociation of the ligand (L) from the protein (P) is given by the equation the dissociation constant Kd for the reaction is P L PL . 3.7.2 Transition-State Theory Transition-state theory states that all reactants should raise from their initial state to a more energetic state, called the transition state, before the reaction can take place. This energy...

Summary Learning Outcome

Back to visualization of the reaction with which we started CH3Cl + NaOH CH3OH + NaCl Figure 2.5 Three-dimensional geometry of differently hybridized carbons. Now we can appreciate what we mean by CH3Cl or CH3OH. These two are molecules having covalent bonds. In both of these three hydrogens are connected to the central carbon atom to which in one of the molecules a chlorine and in the other a hydroxyl group is attached. Both of these molecules contain polar covalent bonds between the carbon...

Primary Structure

As we have already mentioned, all proteins contain amino acids joined covalently in a series. The covalent chain structure of these can be written as R 2R3R4R5 .Ri .Rn, where Ri gives the identity of the ith residue in the chain. A unique feature of proteins that distinguishes it from many synthetic polymers is that the units are arranged in a head-to-tail (directional) fashion. Thus, the abbreviations RaRb and RbRa refer to molecules that have different covalent structure and hence will have...

Problems

What are the operating regimes in a bubble column reactor 2. When do you prefer a tower bioreactor to a stirred contactor 3. What is the mechanism of mixing in a bubble column 4. What is the driving force for liquid circulation in a air-lift reactor 5. How do you reduce the backmixing effects in a bubble column 6. What will be the effect of doubling gas velocity in a bubble column on gas-phase holdup 7. How do you estimate power input in operation of a bubble column 8. What is the source of...

Definitions And Explanation Of The Terms Encountered In Stereoselective Synthesis

When there are two functional groups closely related, but slightly differing in their stereo or electronic factors, in a molecule, a given reagent may react preferentially with one rather than the other. Such a reaction is sometimes termed chemoselective. When more than one (normally two) products are formed, but one is formed in greater proportion, the term selective applies. On the other hand when only one functional group reacts (or only one product forms), the term specific applies. Thus,...

Pervaporation

Pervaporation (PV) is the separation of liquid mixtures by vaporization of one of the species through a permselective membrane. Permeate first vaporizes, travels through the membrane by diffusion, and condenses into liquid on the permeate side (Fig. 13.10). The driving force here is vacuum applied on the permeate side. PV is an enrichment technique similar to distillation. The heart of the PV is a nonporous membrane, which either exhibits a high permeation rate for water but does not permeate...

Graphical Approaches

Four different approaches are described below for determining the MichaelisMenten constant from experimental data using graphical techniques. Figure 7.3 describes the first graphical approach. Here the constants are determined from a graph of initial rate (rAo) and initial substrate concentration ( CA 0). Rearranging the Michaelis-Menten equation Eq. (7.9) gives The second approach consists of drawing a graph of rAo vs. rAo CA o, which will give a straight line with an intercept of Vmax and...

Liquid Liquid Extraction

Here two miscible solutes are separated by a solvent, which preferentially extracts one of them. Close boiling mixtures or solutes that cannot withstand high temperatures in distillation may often be separated by this technique. The extraction method uses the differences in solubilities of the components in the solvent. Ethanol from fermentation broth is recovered by extraction. Two main designs of extractors are mixer-settler and column type. In the first design, the solvent and the mixture...

Mixing In Stirred Conditions

Mixing in everyday uses means blending of two or more materials. The scale of mixing is decided by the smallest size of a sample from the mixture that shows inhomogeniety or difference in properties from those of its surrounding. In practice, the scale of mixing is much higher than the molecular scale and much smaller than the system itself. For homogeneous mixtures, the scale of mixing is almost at molecular level given sufficient time, for example, when a water-soluble substrate, such as a...

Mechanism of the Coenzyme

The aldehyde group of the pyridoxal phosphate condenses with amino group of the substrate to form an imine (schiff base) (Fig 4.31). The pyridine ring in the schiff base acts as an ''electron sink'', which very effectively stabilizes the negative charge. Hence protonation of pyridine ring is essential for catalysis. It is the direction of this delocalization that dictates the reaction type and in model systems more than one reaction pathway is often observed. Thus the Baeyer-Villiger oxidation...

H3CCH2 CHj

Figure 2.9 Structural formula of w-propane. The difference in the three-dimensional placement of the constituent atoms having the same connectivity but vary from one another in having different torsional angles the stereoisomers the conformational isomers The constitutional isomers can be conveniently depicted by the standard 2D structural formulas, while for representing the stereoisomers a 3D stereo representation is adopted (Fig. 2.10). 1 -chloro propane (( HtCI) 2-chloro propane Figure 2.10...

Uncompetitive Inhibition

Here the inhibitor binds only to the enzyme-substrate complex producing a dead-end complex, thereby preventing product formation. This type of inhibition is not generally observed, and one example is the inhibition of aryl-sulphatase by hydrazine. The inhibition can be represented as The Michaelis-Menten kinetic equation will be of the form The Lineweaver-Burk equation at initial conditions will be 1 + I q K + Km Vmax (7 23) The intercept will vary while the slope will remain constant for...

Info

This difference may become very important on the larger scales as the mixing efficiency decreases with the scale. For heterogeneous conditions the mixing in the gas phase may also become a point of concern. In most well-agitated vessels the gas phase can be considered to be well mixed in the same way as the liquid phase. When the gas is sparged in the eye of the impeller, which is usually the practice, the impeller blades break up the bubbles into smaller bubbles....

Noncovalent Interactions

Noncovalent interactions are of paramount importance in biologic systems. These form the basic framework for the three-dimensional shape of the innumerable biomolecules (mostly polymers). These interactions also determine the geometry, rate, and dynamics of interactions between the biomole-cules, such as protein-DNA interaction, lipid-protein interaction, and protein-protein interaction, apart from determining the interaction of auto-coids and xenobiotics (drug molecules included) with the...

References

Chem Eng Commun 1995, 73, 273. 2. Pangarkar, V.G. Yawalkar, A.A. Sharma, M.M. Beenackers, A.A.C.M. Ind Eng Chem Res 2002, 41, 4141. 3. Einsele, A. Finn, R.K. Ind Eng Chem Proc Des Dev 1980, 19, 600. 4. Einsele, A. Proc Biochem 1978, 7, 3. 5. Middleton, J.C. Proceedings of Third European Conference on Mixing. 6. Feijen, J. Heijem, J.J. van't Riet, K. Proceedings of the Symposium on Mixing and Dispersion Processes, Institute of Chemical Engineers, Delft Technology...

Soil

The in situ physical and chemical treatment methods for contaminated soil, sediment, bedrock, and sludge include chemical oxidation, electrokinetic separation (this technique involves passing an electric current during which the metal ions move toward the cathode and the anions toward the anode in addition the current creates an acid front at the anode and a base front at the cathode), fracturing (achieved using explosives or pneumatic pressure), soil flushing using solvent and cosolvents, soil...

Series Editor

Bioprocess Sciences Pharmacia Corporation Chesterfield, Missouri Membrane Separations in Biotechnology, edited by W. Courtney McGregor Commercial Production of Monoclonal Antibodies A Guide for Scale-Up, edited by Sally S. Seaver Handbook on Anaerobic Fermentations, edited by Larry E. Erickson and Daniel Yee-Chak Fung Fermentation Process Development of Industrial Organisms, edited by Justin O. Neway Yeast Biotechnology and Biocatalysis, edited by Hubert Verachtert and Ren De Mot Sensors in...

Competitive Inhibition

Two types of inhibition are possible here Active Site Binding. Here the inhibitor is a compound, which has a close structural and chemical similarity to the substrate of the enzyme. Because of this similarity the inhibitor binds to the active site in place of the substrate. The inhibitor simply blocks the active site, and it is impossible for both of them to bind to the active site at the same time. Malonate is a competitive inhibitor of the reaction succinate to fumarate catalyzed by succinate...

Chemical Forces

Adsorption is a technique widely used here achieving high cell loadings. Internal mass transfer becomes a problem with porous support particles. Adsorption capacity and strength of binding are important parameters in designing such systems. Covalent binding is stronger than adsorption and also avoids cell loss through shear. However, when cells grow exponentially, they will be lost into the suspension. Further strong binding could affect cellular metabolism and also enhance diffusional...

Thiaminedependent Enzymes

Just as the oxido reductases require a coenzyme cofactor to bring about the oxidations or reductions, there are a number of other enzymes that also require a nonprotein cofactor or coenzyme to aid in the reaction. Among the sulphur-containing coenzymes thiamine (often referred to as vitamin B1) is the most important. The structure of thiamine pyrophosphate (TPP) or thiami-nediphosphate (ThDP) is shown in Fig. 4.70. It consists of two subunits, a pyrimidine ring and a thiazolium ring. Thiamine...

Batch Cycle Time

The overall processing time not only includes the reaction time but also the times for charging of raw materials, heating the reactants, cooling the products, and discharging. These times are generally negligible in the lab but are often longer in the plant, of the order of several hours. This is very relevant in batch fermentors. For example, it takes about 1.5 to 2 h to fill a 10 kl vessel via a 5-cm-diameter pipe. Cooling the contents of a reactor could be of the order of 1 to 2 h....

Mass Transfer In Bioreactors

Proper supply of all nutrients to each of the cells may not be achieved. Inmost fermentation processes, under aerobic conditions, the supply of oxygen is a crucial factor. Oxygen is sparingly soluble in a aqueous medium (1.25 x 10 6 mol cm3 atm), and it has to pass through a series of resistances in order to get consumed. A number of steps are involved in the process as shown in Fig. 10.3. The overall mass transfer process consists of Transfer from bulk gas phase to gas-liquid interface...

Biological Waste Air Treatment

Two different approaches are followed for treating waste air. The first treatment method consists of use of biofilters, trickling filters, or bioscrub-bers. In all these setups microorganism is supported on solid carrier and the waste air component is destroyed when it comes in contact with the biomaterial. The contaminated air flows over the bed on which biocultures that degrade the pollutants are supported and during its flow pollutants are transferred from the gas to the biofilm and are...

Gas Holdup

The area available for mass transfer at the gas-liquid interface depends on the amount of the dispersed phase and also on the degree of dispersion. In bioreactors, the gas phase is usually the dispersed phase in a large quantity of liquid. The volume of gas in the reactor is usually expressed in terms of fractional volume of the reactor occupied by the dispersed phase. Fractional gas holdup( G) --(10.21) The gas dispersion can also be written in terms of velocities of the two phases in flow...

Nomenclature

A Specific surface area of gas-liquid interface, m-1 as Specific surface are of solid particles, m-1 Concentration of A in gas phase, mol m3 Concentration of A in liquid phase, mol m3 Concentration of A in liquid phase in equilibrium with the gas Dispersion coefficient in gas phase, m2 s Dispersion coefficient in liquid phase, m2 s Molecular diffusivity of solute, m2 s Dispersion coefficient in solid phase, m2 s Diameter of bubble at the orifice, m Gas side mass transfer coefficient on gas...

Gas Dispersion And Holdup In Tower Bioreactors

A decisive mass transfer problem in the majority of fermentations constitutes the transport of oxygen from the air phase to the locale of the reaction, i.e., the biomass phase, which, in accordance to the chemical engineering, will be referred to as the solid phase. The major reason that oxygen transfer may play an important role in biological processes is the limited oxygen capacity of the fermentation broth due to the low solubility of oxygen. The fractional gas holdup ( G) is an important...

Dmh1127

Experimentally, (ka G) is found to be proportional to P0 8 at a laboratory scale 11 . In addition, the ratio is inversely proportional to square root of viscosity. The gas holdup increases until limited by the reducing efficiency of the impeller, which becomes flooded with gas. Values of G in this region usually do not exceed 30 . The value of 20 can be used for estimation. As virtually all microbial systems contain added antifoam, it is recommended that (ka G) be reduced by 40 relative to pure...

Gas Liquid Mixing

Large tanks tend to have a wider bubble size distribution than smaller tanks. One major principle to be followed for the design of a mixing equipment is that the impeller blade must be two or three times larger than the largest bubble droplet, particle, or fluid '' clump'' that is of importance to the process. Blend time decreases in the presence of gas bubbles. Thus the percentage of gas holdup is an important factor in scale-up. The linear superficial gas velocity increases on scale-up, and...

Physical Means

Physical entrapment is a technique most widely used and consists of using porous polymers such as agar, alginate chitosan, and gelatin silica gel and polystyrene. The beads must be prepared in the presence of cells so that they get entrapped during the preparation process. Preparation techniques include 1. Gelation of polymers Here liquid polymer is mixed with a cell suspension and templates are used to create beads Figure 5.5 Experiment 5 biotransformation of organic sulfides. Figure 5.5...

Covalent Bond

The type of bonding when electrons are shared equally, between the two bonded atoms, is known as a covalent bond. The same octet rule (duet rule for hydrogen), is often obeyed not by the transference of one electron from one atom to the other, as in the ionic bond, but by sharing of the two bonding electrons. This is formed between elements that in general are not readily ionizable, that is, they are neither strongly electropositive nor strongly electronegative. The electron density of the two...

Solid Suspension

Scale-up poses no problem for suspending solids up to about 30 by weight. However, concentrated slurries start behaving like viscous pseudoplastic material. The minimum rpm required for suspending solids is a function of particle diameter, and power per unit volume of the liquid is proportional to D '55. Scaling up of biotechnology processes which use animal cells pose problems since these tear at increased shear rate. This happens near the tip of the blade (although average shear rate near the...

Biocell Growth

When a small quantity of living bio cells is added to a solution containing essential nutrients at the correct operating conditions, the cells will grow. Unicellular organisms divide as they grow hence, the increase in number of cells is also accompanied by increase in the biomass. As the cells take in nutrients from the surroundings they release metabolic end products. The growth of the cell population with time is shown in the Fig. 9.3. Upon change of environment the cells go though a phase,...

Mixed Inhibition

The action is termed as mixed inhibition if the inhibitor constant for both the steps is different. E + I W El (inhibitor constant Kt) EA + I W EAI (inhibitor constant Kj) In the Lineweaver-Burke plot the lines will not intersect at the 1 rA or the 1 CA axes. If Kr > Ki, then the straight lines will cross to the left of the 1 rA axis, but above the 1 CA axis as shown in Fig. 7.9a. If Kr< Ki, then the straight lines will cross below the 1 CA axis (Fig. 7.9b). Another mechanism that is...

Hydrophobic Interaction

This interaction is to a large extent unique to biologic systems since it involves the attractive influence of two hydrophobic groups in aqueous environment. It's not glue, suction, or static electricity that keep geckos from falling off the ceiling it may be van de1 Waals forces says new study from UC Berkeley, Lewis & Clark, Stanford. Geckos are able to scurry up walls and across ceilings thanks to 2 million microscopic hairs on their toes that glue on to surfaces in a way that has given...

Scaleup Rules

Geometric similarity fixes the ratio of various lengths with the system. A single ratio (R) can be used to define the ratios of all linear dimensions between the large and small scale. Di Ti bi Zi The rpm of the large vessel and the small vessel will be related as For equal liquid motion or constant Froude number, n 1. This criterion also ensures constant agitator tip speed, which guarantees the velocities leaving the impellers in each case are the same. Impeller tip velocity determines the...

Separation Techniques

The viability of a process depends on the ability to purify and concentrate bioproducts in a cost-effective manner on a commercial scale and to meet the required high purity specification. New processes and major improvement of existing processes are needed to attain this goal. Downstream operations involve three steps 1. Recovery of biomass for reuse or disposal. The processing may involve areas such as cell disruption, post-translational protein processing, protein refolding, protein...

Effect Of Shear On Cells

Since microbial cells are affected adversely by shear, high shear conditions in stirred vessel could be detrimental to the viability of cells. It may be necessary to consider the magnitude of the shear experienced by the cells. The highest shear will be definitely in the vicinity of the agitator while it should decrease as the fluid moves away from the impeller. Croughen et al. 16 defined an integrated shear factor (ISF) as a measure of shear field strength between an impeller and vessel wall....

Structure and Functions

They increase the rate of chemical reactions taking place within living cells, without themselves suffering any overall change. In fact, these are central to life, and it may not be an understatement to say that these molecules sustain life on this planet. Most of the enzymes are proteins, to be more specific globular proteins. Since, some RNAs are also known to act as biocatalysts, it is not correct to say that all enzymes are proteins, but for these few...

Adsorption and Chromatography

Adsorption and chromatography techniques involve capturing (adsorbing) the desired product on a solid adsorbent like ion-exchange resins or activated charcoal, and they can be operated in batch, fluidized bed and expanded-bed mode (4). The feed mixture is first contacted with the adsorbent, and the resin is subsequently eluted with a solvent to remove the adsorbed product. The advantage of this technique over liquid extraction is that much smaller volumes of adsorbent are required (vs. organic...

Correlations For Gas Holdup In Stirred Bioreactors

A number of correlations are available from numerous experimental studies for estimation of holdup of gas phase in stirred conditions and most of them are in the form The constants a, b, and c depend on the type of impeller and combination of impeller in the case of multi-impeller systems. Feijen et al. 6 gave a correlation relating pressure difference across the unit to correct for superficial gas velocity fa 0-13 (V)V3 (mg f (11.30) An other correlation has been suggested by Hughmark 12 ,...

Fermentation

Different types of commercial products that are produced by fermentation can be classified as 1. Biomass, animal feed additive, yeast 2. Metabolic products or primary metabolites antibiotics, amino acids, vitamins 3. Products based on biotransformation 4. Production of microbial enzymes lipases, amylases Advantages of fermentation technology are (1) complex compounds like vitamin B12 and penicillin can be produced in single step and economically feasible means, (2) use of cheap raw materials,...

YDi

For a bubble of diameter db, rising through a liquid phase without much entrainment of the liquid phase, the contact time is approximated as diameter of the bubble divided by the bubble rise velocity. The integration of the flux over the time t 0 to t tc, gives mass transfer coefficient as The mass transfer coefficient dependence on molecular diffusivity in the Higbie's penetration theory is square root type, unlike its direct dependence on Dm in the two-film theory. The hydrodynamic conditions...

Ionic Bond

From the spectroscopic studies of an atom (hydrogen spectrum) it became clear that electrons reside in shells about the nucleus. The outermost shell of electrons in an atom is called the valence shell, and the electrons in this shell are called valence electrons. The German Walther Kossel noted (1916) that stable ions tend to form when atoms gain or lose enough electrons that they have the same number of electrons as the noble gas of closest atomic number. The same observation was restated as...

Vilas Gajanan Gaikar

Bombay University Maharashtra, India Although great care has been taken to provide accurate and current information, neither the author(s) nor the publisher, nor anyone else associated with this publication, shall be liable for any loss, damage, or liability directly or indirectly caused or alleged to be caused by this book. The material contained herein is not intended to provide specific advice or recommendations for any specific situation. Trademark notice Product or corporate names may be...

Visualization of a Molecule

What do we mean by molecules How do they look Molecules are obtained by a combination of atoms. Atoms can be visualized as an electron cloud with a (heavy) center nucleus. Almost like a hazy mass of spherical cotton ball with seedlike center nucleus. Therefore, when two electron clouds unite, we get another bigger electron cloud with two nuclei placed at a particular distance from one another. Thus, if more than two atoms combine, we get an electron cloud distributed aross all the nuclei of the...

Biochemical Reactor

A wide range of antibiotics, vitamins, amino acids, fine chemicals, and foodstuffs are manufactured biochemically. Detoxification of industrial and domestic waste water is also carried by biochemical means. The heart of a biochemical process is the reactor. In a bioreactor, the transformation of raw materials into desired products is carried out by the enzyme systems, living microorganisms or by isolated enzymes. The reaction products are formed by three basic processes, namely 1. The product...

Solid Liquid Separation Filtration Centrifugation and Sedimentation

The concentration of insolubles in broth could vary from 0.1 to 60 and the insoluble material may be 1 mm or larger in diameter. Filtration is used as an unit operation to remove solids from a slurry solution. Here, the solid or the liquid could be the desired product. The slurry is passed through a bed of fine particles, cloth or mesh, or perforated plates. Filtration could be carried out by applying pressure to the slurry, so as to force it through the filter medium, or using vacuum at the...

Types Of Bioprocesses

Gaden classified fermentation processes into three types. In type 1 process the production is due to result of primary metabolism. The rate of product formation is directly related to the rate of substrate consumption and also to the rate of cell mass produced. Examples of aerobic systems that follow this classification are acetic acid (using Gluconobacter suboxidans), single-cell protein (using Candida utilis, S. cerevisiae) and baker's yeast (using S. cerevisiae). The first system is operated...

Gas Dispersion In Stirred Bioreactors

The purpose of agitation is to create gas holdup by producing small bubbles that, however, because of a low free rise velocity escape slowly from the liquid. Consequently the area available for mass transfer should increase however, the mass transfer coefficient does not change much. In fact, it may show a decrease for very fine bubbles that behave like rigid solid particles. The gas holdup in a stirred vessel is controlled by the energy input and gas sparging rate. At low speeds of agitation...

Chiral Drugs And Intermediates

Chiral drugs business in 2001 reached 100 billion, representing one-third of all drugs sales worldwide. The industry's continuing growth is partly because of the discoveries in fundamental biochemistry. Of the top 100 drugs marketed today, 50 are single isomers. Single isomer drugs sale reached 115 billion worldwide in 1999 (32 of the total drug market) and expected to reach 146 billion in 2003. All this activity on chiral drugs has led the fine chemical producers to develop new...

Types Of Reactors

The biochemical reactors can be broadly classified into submerged and surface reactors 2,6 . In surface reactors the culture adheres to a solid surface and oxygen is supplied from the gas phase to the continuously wetted solid surface. Wastewater treatment employs such designs. In submerged reactors gas-to-liquid mass transfer is achieved by dispersing the gas in the liquid through continuous input of energy. Submerged reactors can be divided into three groups depending upon the nature of the...