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nant ceiI kinetics. The values of the plasmid los probability for different dilution rates can be calculated using Equation (5.29) based on the first-order dacay rate constants detemined by the experhenn The estimated values of p at different situations are kted in Table 5.3. It can be seen that the pmbability of plasmid 10s is nearly constant for aii dilution rates t-sted. The assumption of a constant probability of plasmid los is proved. According to Equation (5.29), the first-order plasmid 10s constants (kf) should be the same as the fmt-order enzyme production decay constants (v). But the results in Table 5.3 shows that the observed values of v an higher than those of kfi This may be expiained by the foiiowing reasons. Fust, during culture the plasmids might have ken losing a part or the whole giucoamylase gene by deletion wNe ntaining the LEU2 gene. It was also possible that the expression of glucoamylase m ed off in order to reduce the metabolic loiid. Furthexmore, an integration of the LEU2 gene encoded on the piasmid into the host chromosome might occur as a result of homologous recombination event (Kuriyama et ai., 1992) since the host ceil was a LEU2 auxotrophic stmin. in the above cases, the resulted ceik were capable of Ieucine synthesis without producing giucoamylase. Such ceUs showed positive results in plasmid detetion since the YNB selective medium used for measuring the fraction of the plasmid-bearing cdi imposes onïy one selection pressun which is based on the Ieucine gene ( Lm) inserted in the piasmid. Finally, the piasmid copy number might have been decnasing with increasing culture time due to uneven partition benHeen mother and daughter ceh. For the 2 pm based yeast plasmid (Yep), the copy number per ceil unially ranges h m 5 to 40 (Caunt et al., 1988).
It may take several generations for plasmid-mg cells to lose ail plasmids Overaii, the plasmid copy number may demase du~g cuiture. The cells with lower copy number di show positive result in phnid detection but produce less glucoamyiase. Becapse of the above reasow, the enyme production may decay faster than the piasrnid-bearing ceii concentration. According to Equation (5.29). the probabïiity of plasmid 105s @) can ako be estirnated based on the tim-order decay constants of the enzyme production (%). Table 5.3 shows that such calculated values of p are higher than the correspondhg estirnated values of p based on fim-order plasmid los constants (RI). This is because the former include both the segregational and stn~cmral instability, as dimissed in the iast section. Table 5.3. First-Order Plamid Los and Enzyme Decay Constants in Continuous Suspension Culture of Recombinant Yeast Strain C4WpGAC9. D (h-') Measund kf (h") p (dimensiodess) based on kl p (dimensiodess) based on 1 0.05 0.0026 0.0520 0.1 160 O. 10 0.0052 0.20 0.0 122 0.0520 0.06 10 0.0990 0.1 115
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BIOREACTOR STUDIES OF HETEROLOGOUS
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nie University of Waterloo requin%
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ate depended on activities of the p
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Acknowiedgments Fmt of aü, 1 am ve
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2.6. Concluding Rernarks ..........
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5.3.3. Simlilated Results for Prese
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Table 1.1. Table 1.2. Table 1.3. Ta
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Figure 2.1. Figure 3.1. Figure 3.2.
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during Continuous Culture in Airlif
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Figure 5.3. Comparison between Mode
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Cell Systern at Glucose Feed Concen
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a .......... growth ratio (dimensio
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Y, ... ethanol yield for fermentati
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foreign plasmids. One major chalien
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than the denanired, inclusion body
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Table 1.2. Strategies for Enhancing
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Table 1.3. Host Cek, Pfasmids, Gene
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1.4. Immo bilized-Cell Bioreactors
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1. Study the gmwth characteristics,
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plasmid are used; or chromaromal DN
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2.2.1. Genetic Factors 2.2.1.1. Pid
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1- fkquently than a plasmid with Io
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Da Silva and Bailey (1991) used the
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LEU2 or TRPI is cloned into the aux
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eported reduced stabiliity in the s
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on metabolic pathways. In the ferme
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OC), oniy about 35% of the populati
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loss @) is dehned as the probabilit
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+ s Dilution Rate = p' = CI,- - K*+
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concentration couid Iead to coexist
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that factors other than immobiiizat
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earing and plasmid-tke =Ils. Gel be
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productivity irrespective of the mo
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inactive and useless. The problern
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Aerobic fermentation osing iamnobih
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(ranghg h m 1 to 7) on citric acid
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celi fraction decreases monotonicai
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(1987) model aliows for plasmid ins
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affect plasmid stability have ben o
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CEtAPTER 3 MATERIALS AND METHODS 3.
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stiU deleted hm the plasmid. Such p
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1) Reagent solution preparation was
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nonse1ective agar plates, but only
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working Liquid volume. The aeration
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3.5. UNnobilized Ceil Culture 35.1.
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3.52 Cd Lmmobiiization Yeast attach
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3.6. Experimental Error and Reprodu
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-0-Cell(1) +Total CeII (2) 4- Ethan
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* . I I a O 2 4 6 8 10 12 14 Batche
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Cell Maso, Glucose and EthanoI(g1L)
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4.2.2. Batch CuIture in Stirreà-Ta
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[t ~lucoamylase (ALR) -e Glucoamyla
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The finai giucoamyiase concentratio
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Bentley and Kompala, 1989; Satyagal
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160 First ExponenUaI Phase 1 -c ALR
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Figure 4hl. Pathways of Yeast Intem
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fermentation (using nitrogen spargi
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43. Continuous Suspension Culture C
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Figure 4.9. Continuous Suspension C
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1 +Enzyme +Fradlan of PBC +CeIl Mas
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Figures 4.12 and 4.13 show that by
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Fi- 4.13. Cornparison of Glu~iase C
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where 6 = p- - p' + pp*, which is a
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Figure 4-14. Effeds of Dilution Rat
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Impoolsup et ai. (1989a) and Hardji
Page 131 and 132: Figure 4.16. dB/dt versus B Plots a
Page 133 and 134: Figure 4.17. Totai Cell Mas at Diff
Page 135 and 136: another recombinant yeast (impoolsu
Page 137 and 138: other recombinant yeast under nonse
Page 139 and 140: 4.3.4. Effixt of Dilution Rate On R
Page 141 and 142: Figure 4.18- Etlects of Mluiioa Rat
Page 143 and 144: Number of Generations - - - - - - *
Page 145 and 146: B Table 4.5. Metabolic Pathway Anal
Page 147 and 148: concentration. But this may be more
Page 149 and 150: [+ Enzyme (ALR) + Enzyme (STR) +Fra
Page 151 and 152: necessary for host ce& to grow in t
Page 153 and 154: Glucoamylase ConcentraUon (unltsll)
Page 155 and 156: [a Selective Medium A Nonseiective
Page 157 and 158: 5.1 Introduction CHAPTER 5 MODELING
Page 159 and 160: handle. excess glucose is femented
Page 161 and 162: The carbon fluxes h m the three met
Page 163 and 164: 53. Modei Simulation in Batch CuItu
Page 165 and 166: Table 5.1. Summary of Parameters fo
Page 167 and 168: 1 n Glucose o Cell Mass O Ethano1 A
Page 169 and 170: detennined in the cunent study, the
Page 171 and 172: Figure 5.4. Cornparison between Mod
Page 173 and 174: equations are üsted in Appendix G.
Page 175 and 176: a dilution rate at which the giucoa
Page 177 and 178: [ o Expetfmental data -Simuiated mt
Page 179 and 180: The effixts of dilution rate on the
Page 181: Ttme (hrs) 1 a Enzyme A Phsrnid-Bea
Page 185 and 186: understanding of the nature of the
Page 187 and 188: On the other hand. the net accumula
Page 189 and 190: Differentiating Equation (6.20) res
Page 191 and 192: Enyme collcentration m the t>ioreac
Page 193 and 194: Glucoamylase Concentration (units/L
Page 195 and 196: 50 100 150 200 Time (hrs) 1 O Free
Page 197 and 198: F i 6.6. Cornparison of Fnx Cd Mars
Page 199 and 200: . - O 50 100 150 200 250 nme (hrs)
Page 201 and 202: Nasi et ai.. 1988) and recombinant
Page 203 and 204: estimated by using Equation (6.24)
Page 205 and 206: [a lmmobilked System O Free System
Page 207 and 208: oxidation pathway. W~th increasing
Page 209 and 210: O 50 100 150 200 250 300 Tirne (hrs
Page 211 and 212: epeated batch fermentations, the fe
Page 213 and 214: Glucoamylase Concentration (unitslL
Page 215 and 216: 6) Suitable for repeated-batch and
Page 217 and 218: ecause glucose fermentation dominat
Page 219 and 220: cells. Tests of the proposed model
Page 221 and 222: 7.2. Recommendations The foUowing f
Page 223 and 224: APPENDIX A: PLASMID MAP FOR pGAC9 l
Page 225 and 226: where Bi (Biot number) = - ks De @
Page 227 and 228: APPENDK C. EFFECTS OF INITIAL GLUCO
Page 229 and 230: Figure C.2. Effect of Initial Gluco
Page 231 and 232: Figure C.4 Effect of Initial Glucos
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APPENDLX D. COMPARISON OF ORIGINAL
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(continue)
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(continue)
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(continue)
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E.2. Batch Fermentation with Recomb
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(continue)
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(continue) tfhJ 0.5 10.5 12.75 12.5
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(continue)
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E.3.2. Experimental Data (Parker an
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Run No: CALE (Selected Strain. D =
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Run No: CALR 5 (Original Suain, D =
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Run No: CSTR3 (Selected Suain, D =
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(continue)
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Run No: CICR2 (Selected Suain, D =
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Run No: CiCR4 (Selected Suain, D =
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Eh. Repeated Batch Culture in hmobi
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APPENDIX F. C CODE FOR THE PROPOSED
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* the initial data */ /* gening the
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* getting the founh term in R-K met
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I*Plasrnid-bearing ceU concentratio
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* Func tion C 1 */ îloat C l(float
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APPEMIM G. EXAMPLES OF MAPLE V CODE
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REFERENCES Ataai. MM. and Shuler. M
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Caunt, P.. hpoolsup, A.. and Greenf
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cuitanes of E. coli BZ18@TG 201) wi
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Gabrieisen. O.S. et aL (1990), Effi
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Huang, C-T., Peretti, S.W., and Bry
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Kim, B.G. and Shuler, M.L. (1990a),
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Lee, S.B.. Ryu, D.D.Y., seigel, R,
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Nasri, M., Sayadi. S.. Barbotin, J.
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Pin, S.J. and Kmwski. W.M. (1970),
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Seo, I-H. and Bailey. J.E. (1985).
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Tumer. B.G., Avgerinos G-C.? Melnic
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Yu, J. and Tang, X (Editor, 1991),
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