• KSBB Journal
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• v.6 no.1
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• pp.85-90
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• 1991

Experiments of alcohol fermentation of the yeast,K. fragi1is CBS 1555 were performed to obtain the following results. In these experiments, the initial concentrations of sugar which was composed of inulin and fructose as weight ratio of one to one were 30, 50, 75, 100 and 150g/l and the initial densities of the microorganism were less than 0.5g/l, 10g/1 to 15g/1, and 50g/l. The functional relationship among specific growthrates, sugar concentrations, and alcohol concentrations could be expressed by Aiba-shoda equation and the specific growth rate represented the trend that decreased with increase in the initial concentration of the microorganism. Also, $\mu$max and Ks of Monod's equation could be expressed as the function of initial cell concentration like the following equations. $\mu$max=0.8-0.008X Ks=0.54X+8 In the region that sugar, alcohol and cell concentrations were 10g/1 to 120g/l, 0g/l to 60g/l and 0.5g/l to 50g/l respectively, the differences between the experimental values and the calculated ones for specific growth rate approached to 40% with respect to experimental values at the worst cases, but in most cases, those were distributed in the range of less than 20%.

• Microbiology and Biotechnology Letters
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• v.21 no.4
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• pp.354-365
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• 1993

A novel control method with automatic tuning of PID controller parameters has been developed for efficient regulation of dissolved oxygen concentration in fed-batch fermentations of Escherichia coli. Agitation speed and oxygen partial pressure in the inlet gas stream were chosen to be the manipulated variables. A heuristic reasoning allowed improved tuning decisions from the supervision of control performance indices and it coule obviate the needs for process assumptions or disturbance patterns. The control input consisted of feedback and feedforword parts. The feedback part was determined by PID control and the feedforward part is determined from the feed rate. The proportional gain was updated on-line by a set of heuristics rules based on the supervision of three performance indices. These indices were output error covariance, the average value of output error, and input covariance, which were calculated on-line using a moving window. The integral and derivative time constants were determined from the period of output response. The specific growth rate was maintained at a low level to avoid acetic acid accumulation and thus to achieve a high cell density. The specific growthe rate was estimated from the carbon dioxide evolution rate. In fed-batch fermentation, the simutaneous control of dissolved oxygen concentration (at 0.2; fraction of saturated value) and specific growth rate (at 0.25$hr^{-1}$) was satisfactory for the entire culture period in spite of the changes in the feed rate and the switching of control input.

• Journal of Microbiology and Biotechnology
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• v.9 no.6
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• pp.789-793
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• 1999

The effect of acetic acid formation deficiency on recombinant E. coli fermentation was investigated using a mutant strain deficient in acetic acid formation. A mutant strain which does not grow under anaerobic conditions was isolated. The acetic acid production in this strain was negligible in aerobic batch fermentation. The cloned-gene expression in the mutant strain was higher than the wild-type strain. Fed-batch fermentations with controlled specific growth rates were carried out in order to compare the cloned-gene expression between the wild-type and the mutant strains. The expression decreased along with the specific growth rate in both strains. The cloned-gene expression in the mutant strain was 60% higher than in the wild-type strain at the same specific growth rate.

• KSBB Journal
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• v.13 no.3
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• pp.289-294
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• 1998

The effects of various step-fortifications of the initial medium with amino acids, glucose, and vitamines on the growth and metabolism of a hybridoma cell line in batch cultures were quantified. Comparisons between the metabolic rates of the various cultivations were made for the exponential growth phase. Fortification of the basal medium resulted in higher cell densities through a prolonged growth phase, but the maximum specific growth rate was not affected. The uptake rate of glutamine increased with the addition of amino acids but did not change upon the addition of glucose or vitamines. The specific glucose consumption decreased slightly with the addition of amino acids but increased production of lactate and {{{{ { NH}`_{4 } ^{ +} }}}}. A reciprocal relationship between the yields of {{{{ { NH}`_{4 } ^{+ } }}}} and lactate indicated a joint regulation of glycolysis and glutaminolysis.

• Journal of Korean Society of Water and Wastewater
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• v.33 no.1
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• pp.55-62
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• 2019

The respirometric technique has been used to analyze the nitrification process in a sequencing batch reactor(SBR) treating municipal wastewater. Especially the profile of the respiration rate very well expressed the reaction characteristics of nitrification. As the nitrification process required a significant amount of oxygen for nitrogen oxidation, the respiration rate due to nitrification was high. The maximum nitrification respiration rate, which was about $50mg\;O_2/L{\cdot}h$ under the period of sufficient nitrification, was related directly to the nitrification reaction rate and showed the nitrifiers activity. The growth rate of nitrifiers is the most critical parameter in the design of the biological nutrient removal systems. On the basis of nitrification kinetics, the maximum specific growth rate of nitrifiers in the SBR was estimated as $0.91d^{-1}$ at $20^{\circ}C$, and the active biomass of nitrifiers was calculated as 23 mg VSS/L and it was about 2% of total biomass.

• KSBB Journal
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• v.13 no.5
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• pp.469-476
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• 1998

Among 31 water-born microbial strains isolated from various sites in Korea, strain DJ-4 was selected as a test organism for toxicity measurements in that its growth was completely inhibited by the presence of 668.4 mg/L of chloroform and 297.5 mg/L of toluene in the liquid LB medium whereas others did not. It was observed that lag periods and specific growth rates of DJ-4 batch vial cultures were prolonged and decreased, respectively, by phenol, benzene, toluene, ethylbenzene, p-xylene, perchloroethylene, trichloroethylene, and chloroform at the concentrations between 3.6 and 417.8 mg/L. There changes were found to be linear with respect to the concentrations of the toxic compounds. From the first-order regression equations, 50% effective concentrations (EC50${\mu}$ for concentrations of toxic compounds causing 50% decrease of specific growth rates and EC50lag for 50% increase of length of lag periods) were calculated for each compounds. By comparing DJ-4 EC50${\mu}$ values with Daphnia LC50's from a literature for benzene, ethylbenzene, toluene, and trichloroethlyene, it was concluded that microbial specific growth could be a new, fast, and reliable parameter for toxicity tests.

• The Korean Journal of Malacology
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• v.30 no.3
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• pp.227-234
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• 2014

The effect of different feeding rate on the growth and survival rate of the abalone, Haliotis discus hannai, were investigated in marine net cage culture and indoor tank culture. Feeding rate is determined that was fed 5, 10, 15 and 20 percentage to abalone at body weight once daily : 5 daily feeding rate (DFR), 10DFR, 15DFR and 20DFR. After that, it was conducted to reared during thirteen month with two replicates in net-cage culture and indoor tank culture. In the growth performance of reared abalone (initial mean shell length $54.18{\pm}7.39mm$) in net cage culture, that the absolute growth rate (ARG), daily growth rate (DGR) and specific growth rate (SGR) to the shell length and shell breadth, as well as weight gain (WG), daily weight gain (DWG) and specific weight gain (SWG) to body weight of 20DFR were lower than those of different groups (P < 0.05). Also, survival rates of 20DFR was lower than those of different groups (P < 0.05). In the growth performance of reared abalone (initial mean shell length $49.70{\pm}2.28mm$) in indoor tank culture, that the ARG, DGR and SGR to the shell length and shell breadth, as well as WG, DWG and SWG to body weight of 5DFR and 10DFR were lower than those of different groups (P < 0.05). And also, survival rates of 20DFR was lower than those of different groups (P < 0.05). Therefore, these results is showed that the daily feeding rate for natural feed in net-cage culture and indoor tank culture should be to supply among 5-10 percents, taking into account growth, survival rate and economical efficiency.

• Journal of Korean Society of Environmental Engineers
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• v.33 no.8
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• pp.591-597
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• 2011

The purpose of this study was to determine optimum conditions for the cultivation of Chlorella sp. FC-21 using light emitting diodes (LEDs). Specific growth rate and cell concentration were measured for the reactors at the illuminations of different wavelengths of LEDs. Among various types of LEDs, red LEDs were the most effective light source, and also greatest increases of specific growth rate and cell concentrations were obtained when light intensity of red LEDs increased. The specific growth rate decreased when initial cell concentration increased due to the shading effect of each cell in the reactor. To determine beneficial effect of aeration to cell cultivation, micro-air bubbles were aerated at 0.35 vvm in the reactor at the illumination of red LEDs. Two and ten times greater specific growth rate and cell concentration were obtained when aeration was applied. From this study, we found that red LEDs with aeration were the most appropriate light source for the cultivation of Chlorella sp. FC-21.

• KSBB Journal
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• v.15 no.6
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• pp.670-672
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• 2000

Azotobacter vinelandii UWD synthesizes poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV), one of the biodegradable polymers, when odd and even number carbon sources are simultaneously added to a medium. In this study, we investigated the specific growth rate of Azotobacter vinelandii UWD on propionic acid and valeric acid. The specific growth rates were $0.183 hr^{-1} and 0.137 hr^{-1}$ at 1.0∼1.5 g/L of propionic acid and 1.0 g/L of valeric acid, respectively. When a mixture of 0.75 g/L of propionic acid and 0.5 g/L of valeric acid was added to the medium, the specific growth rate was 0.196 hr(sup)-1, which was equal to or higher than those of the individual organic acids. Among 10∼50 g/L of glucose cell growth was best at 20 g/L.

• Microbiology and Biotechnology Letters
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• v.23 no.4
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• pp.479-484
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• 1995

The effect of initial cell concentration on the characteristics of ethanol fermentation was investigated in the batch fermentation of Saccharomyces cerevisiae ATCC 24858. The characteristics were investigated in the range of 60 to 230 g/l of the initial sugar concentrations and 0.5 to 85 g/l of the initial cell concentrations. When the initial cell concentrations were 27 g/l for 60 g/l of the initial sugar and 85 g/l for 230 g/l, the fermentation time required for the complete consumption of the initial sugar was one hour, respectively. The ethanol productivity increased with the initial cell concentration so that, in the case of 100 g/l of initial sugar, the productivity rose up to 55 g/l/hr at 55 g/l of the initial cell concentration. The specific growth rate decreased according to the increase in the initial biomass concentration and finally became zero at around 25 g/l of the cell concentration regardless of the initial sugar concentration. The specific ethanol production rate was constant as 1.02 g/l/hr up to 150 g/l of the initial sugar. However, the rates decreased sharply with the augmentation of concentration of the initial sugar above 160 g/l. The overall ethanol yield represented a constant value, 0.475 g/g irrespective of the initial cell and sugar concentrations. The overall biomass yietd showed a trend to diminish in values with the biomass and ultimately to reach zero more than 25 g/l of the initial cell concentration.