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centration dropped to about one-sixth of its maximum value. Evidently, the decay of enzyme concentration in the bioreactor is due to the plasmid insmbility. Even though the total ceii mas in the bioreactor nmained &y constanf the Mon of the plasmid- bearing ceil continuously decreased 4.10 and 4.1 1). Growth advantage of plasmid-free ceh could be another reason that was respomible for the &op of the proportion of plasmid- bearing ah. During the continuous ceil culture process, celis lacking the plasmid compte successfiilly with plasmid-bea~g ce& in mixed culnue. Eventually, the plasmid-bearing cells will be ovenaken by plasmid-fne cea. in continuou culture experiments ushg the selected strain, both the fraction of plasmid-bearing ce& and enzyme concentration were foUowed. Figures 4.10 and 4.1 1 show that both the enzyme concentration and the Mon of piasmid-bearing ceb decreased with culture the. Thus. the proportion of plasmid-karing ceh was directiy related to glucoamyiase concentration in the bioreactor. This relationship was ais0 found at different dilution rates in continuous suspension culhue ( See Section 4.3.4). 43.2. Cornparison between Original and Seleeted Strains The original strain npresented the recombinant S. cerevisiae C468lpGAC9 originally obtahed h m ATCC. The selected saain was obtained according to a meening protocol described in the Chapter 3 ( Section 3.2 ). The cornparisons of enzyme concentration between the onguial and selected strains in continuous suspension cuiture in the YPG nonseiective medium are dernonsaated in Figtue 4.12 (in Sm) and Figure 4.13 (in ALR).
Figures 4.12 and 4.13 show that by ushg the selected saain the enzyme concentration doubled in both STR and ALR bioreactors even though the total œIi concentrations in the bioreactor were a little lower than that ushg the onguial saain. This is because after the double pressure selection. the selected strain contained a high proportion of plasmid- bearing ab. These cells conrained both the giucoamylase and LEU2 genes and could encode glucoamyiase effectively. It is interesthg to note that the decay of the enzyme concentration in the reactor followed an exponential p am and the fîrst-order decay rate constant for selecwl strain was slightly maller (Figures 4.12 and 4.13). This suggests that the plasmid stability was enhanced after the recombinant cells experienced double selection pressure. Since the growth rare is very slow in the dooble seleaion medium. it is not practical to use the double selection medium in industrial fermentation. But double selection could be an effective way to men and maintain recombinant ceik during the inoculurn preparation stage. In this research, screening under double selection pressure was performed every three months in order to keep the engineered genetic properties of the present recombinant yeast Then the selected arain was maintained in the double selection medium.
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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
Page 69 and 70: Aerobic fermentation osing iamnobih
Page 71 and 72: (ranghg h m 1 to 7) on citric acid
Page 73 and 74: celi fraction decreases monotonicai
Page 75 and 76: (1987) model aliows for plasmid ins
Page 77 and 78: affect plasmid stability have ben o
Page 79 and 80: CEtAPTER 3 MATERIALS AND METHODS 3.
Page 81 and 82: stiU deleted hm the plasmid. Such p
Page 83 and 84: 1) Reagent solution preparation was
Page 85 and 86: nonse1ective agar plates, but only
Page 87 and 88: working Liquid volume. The aeration
Page 89 and 90: 3.5. UNnobilized Ceil Culture 35.1.
Page 91 and 92: 3.52 Cd Lmmobiiization Yeast attach
Page 93 and 94: 3.6. Experimental Error and Reprodu
Page 95 and 96: -0-Cell(1) +Total CeII (2) 4- Ethan
Page 97 and 98: * . I I a O 2 4 6 8 10 12 14 Batche
Page 99 and 100: Cell Maso, Glucose and EthanoI(g1L)
Page 101 and 102: 4.2.2. Batch CuIture in Stirreà-Ta
Page 103 and 104: [t ~lucoamylase (ALR) -e Glucoamyla
Page 105 and 106: The finai giucoamyiase concentratio
Page 107 and 108: Bentley and Kompala, 1989; Satyagal
Page 109 and 110: 160 First ExponenUaI Phase 1 -c ALR
Page 111 and 112: Figure 4hl. Pathways of Yeast Intem
Page 113 and 114: fermentation (using nitrogen spargi
Page 115 and 116: 43. Continuous Suspension Culture C
Page 117 and 118: Figure 4.9. Continuous Suspension C
Page 119: 1 +Enzyme +Fradlan of PBC +CeIl Mas
Page 123 and 124: Fi- 4.13. Cornparison of Glu~iase C
Page 125 and 126: where 6 = p- - p' + pp*, which is a
Page 127 and 128: Figure 4-14. Effeds of Dilution Rat
Page 129 and 130: 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
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Figure 5.4. Cornparison between Mod
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equations are üsted in Appendix G.
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a dilution rate at which the giucoa
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[ o Expetfmental data -Simuiated mt
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The effixts of dilution rate on the
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Ttme (hrs) 1 a Enzyme A Phsrnid-Bea
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It may take several generations for
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understanding of the nature of the
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On the other hand. the net accumula
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Differentiating Equation (6.20) res
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Enyme collcentration m the t>ioreac
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Glucoamylase Concentration (units/L
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50 100 150 200 Time (hrs) 1 O Free
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F i 6.6. Cornparison of Fnx Cd Mars
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. - O 50 100 150 200 250 nme (hrs)
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Nasi et ai.. 1988) and recombinant
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estimated by using Equation (6.24)
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[a lmmobilked System O Free System
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oxidation pathway. W~th increasing
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O 50 100 150 200 250 300 Tirne (hrs
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epeated batch fermentations, the fe
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Glucoamylase Concentration (unitslL
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6) Suitable for repeated-batch and
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ecause glucose fermentation dominat
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cells. Tests of the proposed model
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7.2. Recommendations The foUowing f
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APPENDIX A: PLASMID MAP FOR pGAC9 l
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where Bi (Biot number) = - ks De @
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APPENDK C. EFFECTS OF INITIAL GLUCO
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Figure C.2. Effect of Initial Gluco
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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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