• KSBB Journal
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• v.14 no.4
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• pp.511-516
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• 1999

The effects of environmental and compositon factors, such as reaction time, metal ions, pH, agitation speed, the weight ratio of water to oil, and the weight of enzyme, on the hydrolysis of oils by Lipase-OF were investigated. In case of oils with low melting point, the optimum temperature of hydrolysis were the enzyme activity was maximum was 37$^{\circ}C$. However, when the melting temperature was higher than 4$0^{\circ}C$, the optimum temperature was around the fusion temperature. The activity of Lipase-OF decreased very rapidly with increase of temperature in the range of higher than 45$^{\circ}C$ and the activity perished above $65^{\circ}C$. The effect of agitation speed was investigated from 150 to 650 rpm. The hydrolysis of oils increased as the agitation speed increased up to 350 rpm, but it did not increase any more above 350 rpm. The weight ratio of water to oil was changed from 1 : 9 to 9 : 1 for the investigation of the effect on the hydrolusis. The weight ratio for maximum hydrolysis was 1 : 1. $Ca^{2+}\;and\;Mg^{2+}$ among various metal ions had some effect on the stimulation of hydrolysis. The optimum concentration of the ions was about 100ppm at which the hydrolysis increased, compared with that of distilled water, by 2 to 3%. The Optimum pH of Lipase-OF was 7. The hydrolysis decreased as the pH decreased as the pH decreased and also decreased as the pH increased. The content of enzyme affected the hydrolysis of oil. The hydrolysis increased with the content of Lipase-OF in the range of less than 0.013 wt% of substrate. However, the increase of hydrolysis with the content of Lipase-OF ceased above 0.013 wt%. The experiments investigating the effect of environmental and composition factors on the hydrolysis of oils showed that the optimum temperature was 37$^{\circ}C$, the pH 7, the concentration of $Ca^{2+}\;or\;Mg^{2+}$ 100 ppm, the agitation speed 350 rpm, the weight ratio of water to oil 1 : 1, and the content of Lipase-OF 0.013 wt% of substrate.

• Applied Chemistry for Engineering
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• v.21 no.2
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• pp.174-177
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• 2010

In this study, non-catalytic transesterification from rapeseed oil using supercritical methanol was carried out by varying the operation parameters such as temperature ($320{\sim}365{^{\circ}C}$), time (0~20 min), pressure (10~35 MPa), molar ratio of oil to methanol (1 : 15~60) and agitation speed (0~500 rpm). In order to evaluate the effects of reaction parameters on the content of fatty acid methyl esters (FAMEs), we carried out the study using a batch reactor. The content of FAMEs increased when the temperature increased. However, the content of FAMEs decreased with temperature above $335^{\circ}C$ and time above 5 min. The content of FAMEs increased with increasing the molar ratio of methanol to oil but the content of FAMEs was slightly affected by molar ratio of oil to methanol above 1 : 45 and pressure above 20 MPa. It was found that the agitation speed above 100 rpm slightly affected the content of FAMEs. The highest content of FAMEs in biodiesel (95%) was obtained under the reaction conditions: temperature of 335 ${^{\circ}C}$, time of 10 min, pressure of 20 MPa, molar ratio of 1 : 45 (oil to methanol) and agitation speed of 250 rpm.

• Korean Chemical Engineering Research
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• v.47 no.5
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• pp.651-654
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• 2009

In this study, non-catalytic transesterification using supercritical methanol was performed for preparation of biodiesel from palm oil. In order to investigate the effects of reaction parameters such as molar ratio of methanol to oil(30:1~60:1), pressure(8~25 MPa), temperature($320{\sim}350^{\circ}C$), agitation speed(0~1,000 rpm) and time(0~20 min) on the content of fatty acid methyl esters(FAMEs), we carried out the study using a batch reactor. With increasing molar ratio of methanol to oil, the content of FAMEs increased. However, the content of FAMEs was little affected by molar ratio above 45 and pressure above 20 MPa. The content of FAMEs increased when the temperature increased. However, the content of FAMEs decreased with temperature above at $350^{\circ}C$ and with time above 5 min. It was found that the agitation speed above 500 rpm scarcely affected the content of FAMEs. The highest content of FAMEs in biodiesel(95%) was obtained under the reaction conditions: temperature of $335^{\circ}C$, pressure of 20 MPa, molar ratio of 45:1(methanol to palm oil), agitation speed of 500 rpm and time of 10 min.

• Journal of Microbiology and Biotechnology
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• v.16 no.11
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• pp.1690-1698
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• 2006

In order to investigate the effect of dissolved oxygen (DO) level on AVM $B_{1a}$ production by a high yielding mutant of Streptomyces avermitilis, five sets of bioreactor cultures were performed under variously controlled DO levels. Using an online computer control system, the agitation speed and aeration rate were automatically controlled in an adaptive manner, responding timely to the oxygen requirement of the producer microorganism. In the two cultures of DO limitation, the onset of AVM $B_{1a}$ biosynthesis was observed to casually coincide with the fermentation time when oxygen-limited conditions were overcome by the producing microorganism. In contrast, this phenomenon did not occur in the parallel fermentations with DO levels controlled at around 30% and 40% throughout the entire fermentation period, showing an almost growth-associated mode of AVM $B_{1a}$ production: AVM $B_{1a}$ biosynthesis under the environments of high DO levels started much earlier than the corresponding oxygen-limited cultures, leading to a significant enhancement of AVM $B_{1a}$ production during the exponential stage. Consequently, approximately 6-fold and 9-fold increases in the final AVM $B_{1a}$ production were obtained in 30% and 40% DO-controlled fermentations, respectively, especially when compared with the culture of severe DO limitation (the culture with 0% DO level during the exponential phase). The production yield ($Y_{p/x}$), volumetric production rate (Qp), and specific production rate (${\bar{q}}_p$) of the 40% DO-controlled culture were observed to be 14%, 15%, and 15% higher, respectively, than those of the parallel cultures that were performed under an excessive agitation speed (350 rpm) and aeration rate (1 vvm) to maintain sufficiently high DO levels throughout the entire fermentation period. These results suggest that high shear damage of the high-yielding strain due to an excessive agitation speed is the primary reason for the reduction of the AVM $B_{1a}$ biosynthetic capability of the producer. As for the cell growth, exponential growth patterns during the initial 3 days were observed in the fermentations of sufficient DO levels, whereas almost linear patterns of cell growth were observed in the other two cultures of DO limitation during the identical period, resulting in apparently lower amounts of DCW. These results led us to conclude that maintenance of optimum DO levels, but not too high to cause potential shear damage on the producer, was crucial not only for the cell growth, but also for the enhanced production of AVM $B_{1a}$ by the filamentous mycelial cells of Streptomyces avermitilis.

• Korean Journal of Psychosomatic Medicine
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• v.20 no.2
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• pp.105-111
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• 2012

Objectives : We investigated the prevalence and composite score of the neuropsychiatric symptoms in patients with mild cognitive impairment(MCI), and dementia of Alzheimer's type(AD). The aim of this study is to analyze the correlation between the result of Korean Neuropsychiatric Inventory(K-NPI) and cognitive function. Methods : A total of 163 patients diagnosed with MCI or AD was divided into three groups(55 MCI patients, 56 dementia patients with mild stage, and 52 dementia patients with moderate, severe stage). We examined neuro-psychiatric symptoms by K-NPI and compared the prevalence and composite score of each subdomain in K-NPI among three groups. Results : The most common symptoms in the MCI group were depression/dysphoria, sleep/night-time behavior, anxiety, and irritability/lability. In mild AD group, the most frequent disturbance was agitation/aggression, depression/dysphoria, anxiety, apathy/indifference, and sleep/night-time behavior. In moderate to severe AD group, the most frequent disturbance was apathy/indifference, depression/dysphoria, agitation/aggression, and delusion. The frequencies of delusion, hallucination, agitation/aggression, apathy/indifference, aberrant motor behavior, appetite/eating change were statistically significant. The total NPI score showed a negative correlation with MMSE-KC and a positive correlation with GDS. Conclusions : Neuropsychiatric symptoms are common features of MCI and AD. These symptoms observed in MCI are similar to those of mild AD. Psychosis is most common in moderate to severe AD, leading to a faster rate of cognitive decline. Therefore, proper management according to the neuropsychiatric symptoms of MCI and three stages of dementia is needed.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.25 no.4
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• pp.301-306
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• 1992

In order to determine the optimal conditions for the process of acetic acid fermentation, the kinetics of Acetobacter aceti fermentation in submerged batch cultures were studied at different agitation speeds and air flow rates. The maximum cell concentration was noted after about 48 hr fermentation and the time course of Acetobactey aceti fermentation showed a distinct feature of growth-associated product formation. At agitation speeds 700, 500, and 300 rpm fixed on air flow rate 1 v/v/M, specific grow rates were $3.97\times10^{-2},\;3.82\times10^{-2},\;and\;2.04\times10^{-2\} \;hr^{-1}$, saturation constants were 61.4, 64.6, and 69.4mg/ml. and volumetric oxygen transfer coefficients were 0.9337, 0.4468, and 0.1701 $min^{-1},$ respectively. At air flow rates 1.25, 1.00, and 0.75 v/v/M fixed on agitation speed 500 rpm, specific growth rates were $3.90\times10^{-2},\;3.82\times10^{-2},\;and\;2.37\times10^{-2}\;hr^{-1}$, saturation constants were 63.4, 64.6, and 64.9 mg/ml, and volumetric oxygen transfer coefficient were 0.4923, 0.4468, and 0.3509 $min^{-1},$ respectively.

• Korean Chemical Engineering Research
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• v.47 no.6
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• pp.740-746
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• 2009

In the present study, the drowning-out crystallization of L(+)-calcium lactate was investigated in order to develop the crystallization separation process. The crystallization of the calcium lactate was induced by injecting the alcoholic anti-solvent into the aqueous solution of calcium lactate and the control of the calcium lactate crystal size during the crystallization was primarily investigated under the consideration of the anti-solvent species, anti-solvent composition and agitation speed as the key operating factors. Alcohols of methanol, ethanol, n-propanol and i-propanol were used as the anti-solvent for the drowning-out crystallization. Prior to the crystallization experiment, the solubility of calcium lactate in the water-alcohol mixture was measured along with the variation of the alcohol species and composition, which was necessary to estimate the supersaturation level of the crystallization. By the drowning-out crystallization, the calcium lactate crystals of the fabric shape were obtained. Using the ethanol as the antisolvent, the fabric crystals close to the needle shape were produced. However, the hairy crystals were obtained by using the propanol as the anti-solvent. Due to such morphological features, the crystals was highly apt to form the aggregates. The aggregation of the crystals was intensified as increasing the alcohol fraction in the water-alcohol mixture. Meanwhile, the agitation caused the breakage of crystals, resulting in the decrease of the crystal size. Therefore, the crystal size in the crystallization was predominantly determined by the competition between the crystal aggregation and breakage.

• Journal of Life Science
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• v.20 no.10
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• pp.1433-1442
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• 2010

Parameters related to dissolved oxygen for the production of pullulan by Aureobasidium pullulans HP-2001 were optimized in 7 l and 100 l bioreactors. The optimal concentrations of glucose and yeast extract for the production of pullulan were 50.0 and 2.5 g/l, respectively, and its conversion rate from glucose was 37% at a flask scale. The optimal initial pH of the medium and temperature for cell growth were 7.5 and $30^{\circ}C$, whereas those for the production of pullulan were 6.0 and $25^{\circ}C$. The optimal agitation speed and aeration rate for cell growth were 600 rpm and 2.0 vvm in a 7 l bioreactor, whereas those for the production of pullulan were 500 rpm and 1.0 vvm. The production of pullulan with an optimized agitation speed of 500 rpm and aeration rate of 1.0 vvm was 18.13 g/l in a 7 l bioreactor. Maximal cell growth occurred without inner pressure, whereas the optimal inner pressure for the production of pullulan was 0.4 kgf/$cm^2$ in a 100 l bioreactor. The production of pullulan under optimized conditions in this study was 22.89 g/l in a 100 l bioreactor, which was 1.38 times higher than that without inner pressure.

• Journal of Environmental Science International
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• v.25 no.9
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• pp.1233-1239
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• 2016

This study aimed to evaluate changes in the TN and TP removal efficiencies, depending on whether or not a settling process is applied, in a sequencing batch reactor (SBR) process with a membrane bioreactor (MBR). Nutrient removal was considered in terms of developing an advanced water treatment system for ships in accordance with water quality standards set forth by 227(64). For these purposes, the TN and TP concentrations in the inflow and outflow water were measured to calculate the TN and TP removal efficiencies, depending on whether or not a settling process was used. Water discharged from a bathroom, which was constructed for the experiment, was used as the raw water. The experiment that included a settling process was conducted twice, and the operating conditions were: aeration for 90 min, settling for 30 min, agitation for 15 min, and settling for 15 min for one experiment; and aeration for 150 min, settling for 45 min, agitation for 15 min, and settling for 15 min in the other. Operating conditions for the experiment that did not include a settling process were: aeration for 180 min and agitation for 60 min. The concentration of the mixed liquor suspended solids (MLSS) in the reactor was 3,500 mg/L, while the aeration rate was 121 L/min and the water production rate was 1.5 L/min. For the two experiments where a settling process was applied, the average TN removal efficiencies were 44.39% and 41.05%, and the average TP removal efficiencies were 47.85% and 46.04%. For the experiment in which a settling process was not applied, the average TN removal efficiency was 65.51%, and the average TP removal efficiency was 52.51%. Although the final nutrient levels did not satisfy the water quality standards of MEPC 227(64), the TN and TP removal efficiencies were higher when a settling process was not applied.

• Applied Chemistry for Engineering
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• v.21 no.5
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• pp.488-494
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• 2010

Under W/O emulsion method using a homogenizer, ${\alpha}$-alumina powder was prepared to evaluate the effects of experimental conditions on its properties, such as particle shape, extent of aggregation, average particle size and distribution. The experimental parameters were the change of type, quantity and composition of emulsifiers as well as the change of O : W volumetric ratio and agitation rate. As results, in the case of the use of single surfactant of SP80, sphere-like particles could be prepared and the average particle size was hardly affected by the agitation speed more than 16000 rpm regardless of SP80 quantity used. When the extent of aggregation among sphere-like particles prepared using $HLB_m$ = 5 of [SP80 & TW80] was compared with that prepared using SP80 at the same vol% surfactant and agitation speed, the former showed more or less low aggregation phenomena and average particle size was slightly reduced. In addition, the fraction of nano-sized particles with low aggregation was increased by the use of 0.1 vol% n-butanol, as a co-surfactant, with $HLB_m$ = 5 of [SP80 & TW80].