• Microbiology and Biotechnology Letters
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• v.16 no.6
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• pp.450-456
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• 1988

For optimal production of L-tryptophan using a regulatory mutant of Escherichia coli the relationship between product formation and acid production was investigated. Experimental results showed that the production level of L-tryptophan was lowered as the specific acid production rate increased. In order to reduce the amount of acid produced during the fermentation, a controlled fed-batch fermentation was employed. In this fed-batch process, the feed rate of the nutrient feed medium was controlled in relation to the oxygen level in the culture and thus the growth of the cells was regulated in such n way that the oxygen demand of the culture could not exceed the oxygen sup-ply. When E. coli cells were cultivated in a controlled fed-batch mode of tormentor operation, the specific acid production rate was significantly reduced and L-tryptophan production was increased as much as five times that obtained in a conventional fed-batch fermentation.

• KSBB Journal
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• v.15 no.5
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• pp.489-496
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• 2000

Several culture systems including batch, two-stage CSTR, semi-fed batch, and two-stage cyclic fed-batch were investigated for the efficient production of the Fab fraction of PDC-E2 specific human monoclonal antibody using high cell density recombinant E. coli. A two-phase batch system and a two-stage continuous system were examined to overcome plasmid instability problems, by separating the growth and the production stages. The cell density and productivity of the two-stage continuous culture was better than that of the two-phase batch fermentation. In the two-stage continuous culture system with DO-stat, the cell growth and the productivity were superior to those of the system without the DO control. Also, almost total plasmid stability was maintained in the two-stage continuous culture system. Modified M9 medium was selected as an optimum feeding medium for the fed-batch process, and the optimum C/N ratio determined to be 2:3. The optimum feeding rate was $0.6g/\ell/hr$ for a constant feeding strategy in semi-fed batch system. When the feeding medium was fed by pulsing, it was observed that more frequent pulsing resulted in improved cell growth. The linear feeding method was the most efficient of the various feeding methods tested. Finally, high cell density culture using a two-stage cyclic fed batch system with pH-stat was tried because the linear feeding method showed limitations in terms of obtaining high cell densities, and a cell density of $54 g/\ell$ was achieved. It was concluded that the two-stage cyclic fed batch system was the most efficient system for high cell density culture of the systems tested. However, productivity improvements were lower than expected due to the extremely high accumulations of acetate, although the low levels of residual glucose were maintained.

• Microbiology and Biotechnology Letters
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• v.27 no.4
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• pp.327-332
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• 1999

A highly productive fed-batch fermentation process was developed for the production of L-ornithine by using a new stabilized strain, Breviabcterium ketoglutamicum BK52. Fed-batch cultures with a continuous feeding of the complex medium were conducted on various operating conditions. The optimal concentration of phosphate in the complex medium was 2.1g/L. The optimal feeding rate of L-arginine was 0.028g/L/hr. The optimal feeding point of the complex medium was determined to be at 40 OD of the cell mass. The final L-ornithine concentrations within 64hrs of cultivation in 5 and 50 liter fermenters were 73g/L and 71g/L, respectively. The maximum overall L-ornithine productivity was 1.14g/L/hr which was about 2 times higher than that of the conventional fed-batch culture with intermittent feeding. The overall productivity of the fermentation system is remarkably improved by employing the optimized conditions, and it offers a significant potential for industrial application.

• Journal of Microbiology and Biotechnology
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• v.12 no.4
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• pp.687-691
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• 2002

To enhance the production of flavonoids [baicalin, wogonin-7-Ο-glucuronic acid (GA)], which are secondary metabolites of Scutellaria baicalensis Georgi(G.) plant cells, a multilayer perceptron control system was applied to regulate the substrate feeding in a fed-batch cultivation. The optimal profile for the substrate feeding rate in a fed-batch culture of S. baicalensis G. was determined by simulating a kinetic model using a genetic algorithm. Process variable profiles were then prepared for the construction of a multilayer perceptron controller that included massive parallelism, trainability, and fault tolerance. An error back-propagation algorithm was applied to train the multiplayer perceptron. The experimental results showed that neurocontrol incorporated with a genetic algorithm improved the flavonoid production compared with a simple fuzzy logic control system. Furthermore, the specific production yield and flavonoid productivity also increased.

• Plant Biotechnology Reports
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• v.4 no.1
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• pp.9-13
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• 2010

Guggulsterone, a hypolipidemic natural agent, is produced in resin canals of the plant Commiphora wightii. In this study, the stimulatory effects of growth retardants [ALAR (N,N-dimethylaminosuccinamic acid) and CCC (chlormequat chloride)] and fungal elicitor on guggulsterone accumulation in cell cultures of C. wightii are reported. CCC at $1\;mg\;l^{-1}$ enhanced guggulsterone content (${\sim}123\;{\mu}g\;l^{-1})$ when added on the fifth day after inoculation, while ALAR at $2.5\;{\mu}g\;l^{-1}$ increased guggulsterone content (${\sim}116\;{\mu}g\;l^{-1}$) when added on the tenth day. In a two-stage fed-batch process, combined treatment with fungal elicitor and growth retardant caused a significant increase (${\sim}353\;{\mu}g\;l^{-1}$) in guggulsterone content in cell cultures after 17 days of growth. This represents an approximately fivefold increase over the guggulsterone contents in initial cultures of this plant.

• KSBB Journal
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• v.14 no.4
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• pp.495-502
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• 1999

The optimization of fed-batch yeast fermentation process has been performed using genetic algorithm(GA). Three strategies were designed and applied to obtain the optimal feed rate profiles. Genes in the chromosome (input variables for optimization) included feed rates on fixed time intervals (strategy I), or swiching times $t_s1\;and\;t_s2$, and feed rates on singular arc (strategy II), or feed rates and the length of time interval (strategy III). Strategy III showed the best results for all initial conditions due to efficient utilization of genetic information. Simulation results using GA showed similar or better performance compared with previous results by variational caculus and singular control approach.

• Journal of Environmental Science International
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• v.6 no.6
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• pp.697-709
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• 1997

Sequencing Batch Reactor(SBR) experiments for organics and nutrients removal have been conducted to find an optimum anaerobic/anoxic/aerobic cycling time and evaluate the applicability of oxidation-reduction potential(ORP) as a process control parameter. In this study, a 61 bench-scale plant was used and fed with night-soil wastewater in K city which contained TCODcr : 10, 680 mg/l, TBm : 6, 893 mg/l, $NH_4^+-N$ : 1, 609 mg/l, $PO_4^{3-}-P$ : 602 mg/l on average. The cycling time In SBRs was adjusted at 12 hours and 24 hours, and then certainly included anaerobic, aerobic and inoxic conditions. Also, for each cycling time, we performed 3 series of experiment simultaneously which was set up 10 days, 20 days and 30 days as SRT From the experimental results, the optimum cycling time for biological nutrient removal with nlght-soil wastewater was respctively 3hrs, 5hrs, 3hrs(anaerobic-aerobic-anoxic), Nitrogen removal efficiency was 77.9%, 77.9%, 81.7% for each SRT, respectively. When external carbon source was fed in the anoxic phase, ORP-bending point indicating nitrate break point appeared clearly and nitrogen removal efficiency increased as 96.5%, 97.1%, 98.9%. Phosphate removal efficiency was 59.8%, 64.571, 68.6% for each SRT. Also, we finded the applicability of ORP as a process control parameter in SBRs.

• Microbiology and Biotechnology Letters
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• v.23 no.1
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• pp.87-90
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• 1995

A process of organically bound germanium preparation was developed for healthy food using inorganic germanium adapted Saccharomyces cerevisiae. Adaptations of Saccharomyces cerevisiae against inorganic germanium were successively carried out through stepwise increase of GeO$_{2}$ concentration in order to produce high quantities of germanium bound yeast. Productivity of yeast and quantities of germanium in yeast were obtained 70.2 g/l and 9780 ppm, repectively, when adapted yeast and fed batch culture were used. Germanium taken-up yeast is to be organically bound germanium by evidence of no difference of germanium content after dialysis.

• KSBB Journal
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• v.15 no.4
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• pp.380-387
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• 2000

An extractive fermentation process using pervaporation was studied in a 7 liter fermentor. Pervaporation was performed using a silicone membrane module and a low-acid-producing strain Clostridium acetobutylicu, B18 was used to produce butanol. In batch culture without pervaporation pH 5.5 and initial glucose concentration of 60 g/L resulted in the highest butanol productivity (0.216 g/L$.$h) with butanol yield of 0.261 Butanol flux through the membrane was best at 2.0 L/min-tubing of air flow rate In batch and fed-batch fermentation glucose consumption rate increased by 1.3 times with pervaporation.

• Biotechnology and Bioprocess Engineering:BBE
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• v.7 no.6
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• pp.371-374
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• 2002

Production of poly(3-hydroxybutyrate-co-3-hydroxyvalerate)［P(3HB/V)］, by fed-batch culture of recombinant Escherichia coli harboring a plasmid containing the Alcaligenes latus polyhy-droxyalkanoate (PHA) biosynthesis genes, was examined in two pilot-scale fermentors with air supply only, In a 30 L fermentor having a XLa value of 0.11 S­$^1$, the final P(3HB/V) concentration and the P(3HB/V) content obtained were 29.6 g/L and 70.1 wt%, respectively giving a productivity of 1.37 g P(3HB/V)/L-h. In a 300 L fermentor having a XLa of 0.03 S­$^1$, the P(3HB/V) concentration and the P(3HB/V) content were 20.4 g/L and 69 wt%, respectively giving a productivity of 1.06g P(3HB/V)/L-h. These results suggest that economical production of P(3HB/V) is possible by fed-batch culture of recombinant E. coli in a large-scale fermentor having low KLa value.