• Transactions of the Korean Society of Mechanical Engineers A
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• v.30 no.5 s.248
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• pp.481-487
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• 2006

Spot-welding is a widely used manufacturing method for thin-sheet components, especially in mass-production industries such as the car industry. Automobiles are often constructed by multi-lap spot welding to secure the passenger from the accident, where optimisation of the welding conditions is a major economic consideration. This research is conducted to investigate weldability characteristics with various welding conditions on the 4-lap spot welded joint of structural steel sheets in automobile. The relationship between the tensile-shear strength and the indentation depth has been investigated to propose the optimum welding conditions. The welding current and the welding time have a greater effect on the welding characteristics than the electrode force. It was found that the electrode force has a relatively close relationship with the expulsion occurrence. The design curves for optimum welding are proposed for the 4-lap spot welded joint.

• Biotechnology and Bioprocess Engineering:BBE
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• v.10 no.1
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• pp.23-28
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• 2005

Lactic acid is a green chemical that can be used as a raw material for biodegradable polymer. To produce lactic acid through microbial fermentation, we previously screened a novel lactic acid bacterium. In this work, we optimized lactic acid fermentation using a newly isolated and homofermentative lactic acid bacterium. The optimum medium components were found to be glucose, yeast extract, $(NH_4)_{2}HPO_4,\;and\;MnSO_4$. The optimum pH and temperature for a batch culture of Lactobacillus sp. RKY2 was found to be 6.0 and $36^{\circ}C$, respectively. Under the optimized culture conditions, the maximum lactic acid concentration (153.9 g/L) was obtained from 200 g/L of glucose and 15 g/L of yeast extract, and maximum lactic acid productivity ($6.21\;gL^{-1}h^{-1}$) was obtained from 100 g/L of glucose and 20 g/L of yeast extract. In all cases, the lactic acid yields were found to be above 0.91 g/g. This article provides the optimized conditions for a batch culture of Lactobacillus sp. RKY2, which resulted in highest productivity of lactic acid.

• Food Science and Biotechnology
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• v.16 no.4
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• pp.526-530
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• 2007

The objective of this study was to establish the optimum alcohol fermenting conditions for the processing of kiwi wine and vinegar products. Six yeast strains were examined for their alcohol production from kiwi at $30^{\circ}C$ for 72 hr with continuous shaking at 100 rpm. Under these conditions, Saccharomyces kluyveri DJ97 produced the highest alcohol content of 10.2%. As the fermentation time extended to 96 hr, the alcohol content reached a maximum of 12.75%. The optimum alcohol fermenting conditions for kiwi fruit were accomplished when kiwi was added to an equal amount of water, inoculated with S. kluyveri DJ97 and fermented at $30^{\circ}C$ for 96 hr with continuous shaking. The content of soluble solids decreased as the alcohol concentration increased, whereas little change was observed in the pH and titratable acidity during the low temperature aging process. Other alcoholic compounds, such as methanol, isopropanol, n-propanol, isobutanol, and isoamylalcohol, tended to increase as fermentation progressed.

• The Korean Journal of Food And Nutrition
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• v.30 no.2
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• pp.319-325
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• 2017

In this study, we optimized the coffee extraction conditions for instant coffee production in two stage percolators, which is the most common coffee extractor for instant coffee production. A central composite design was used to build mathematical model equations for response surface methodology (RSM). In these equations, the yield and overall acceptability of the coffee extracts were expressed as second-order functions of three factors, the feed water temperature, draw-off factor (DOF), and extraction time (cycle time). Based on the result of RSM, the optimum conditions were obtained with the use of desirability function approach (DFA) which find the best compromise area among multiple options. The optimum extraction conditions to maximize the yield and overall acceptability over 40% of yield were found with $163^{\circ}C$ of feed water temperature, 4.3 of DOF and 27 minutes of extraction time (cycle time). These results provide a basic data for the coffee extraction conditions for the competitive instant coffee in the industry.

• Journal of Microbiology and Biotechnology
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• v.24 no.6
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• pp.781-787
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• 2014

2-Ketogluconic acid production by Klebsiella pneumoniae is a pH-dependent process, strictly proceeding under acidic conditions. Unfortunately, cell growth is inhibited by acidic conditions, resulting in low productivity of 2-ketogluconic acid. To overcome this deficiency, a two-stage fermentation strategy was exploited in the current study. During the first stage, the culture was maintained at neutral pH, favoring cell growth. During the second stage, the culture pH was switched to acidic conditions favoring 2-ketogluconic acid accumulation. Culture parameters, including switching time, dissolved oxygen levels, pH, and temperature were optimized for the fed-batch fermentation. Characteristics of glucose dehydrogenase and gluconate dehydrogenase were revealed in vitro, and the optimal pHs of the two enzymes coincided with the optimum culture pH. Under optimum conditions, a total of 186 g/l 2-ketogluconic acid was produced at 26 h, and the conversion ratio was 0.98 mol/mol. This fermentation strategy has successfully overcome the mismatch between optimum parameters required for cell growth and 2-ketogluconic acid accumulation, and this result has the highest productivity and conversion ratio of 2-ketogluconic and produced by microorganism.

• Journal of Sericultural and Entomological Science
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• v.39 no.2
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• pp.101-105
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• 1997

Most of the mulberry saplings in Korea have been produced by grafting. But the production of mulberry sapling by this method is very complex process and requires high level of technique and two years to produce saplings. Therefore, to develop the mulberry sapling production system by softwood cutting method which is suitable for mass production, several conditions on rooting and growth of cuttings were investigated. The rooting ability of cuttings varied according to mulberry varieties, showing the highest rooting ratio of 93.3% in cultivar of Shingwangppong. Of different soil texture as for rooting media, the clay was found to be the best; other media decreased in order as follows; sand, sand loam and vermiculite. The shading ratio by 70% with polyethylene film showed the highest rooting ratio of the cuttings. Optimum day of cutting was around 50th day after sprouting, whereas the ratio of stem thicker than 7mm at the base of saplings in diameter was highest at 44th day.

• Journal of Microbiology and Biotechnology
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• v.5 no.3
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• pp.172-176
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• 1995

Citrate is mainly produced from fungi and oxygen transfer has been known as one of the important factors in citric acid production. A bubble column bioreactor was used for citrate production after pellet was initially made using a stirred bioreactor for the inoculation. The relationship between the pellet size of Aspergillus niger and the oxygen transfer was elucidated by considering morphological characteristics of the pellet. The pellet size was determined by adjusting the impeller speed in the stirred bioreactor and the optimum diameter of the pellet was observed to be 2.2 mm under the experimental conditions. Pellet was maintained quite stable in the bubble column bioreactor and production of citric acid was significantly improved by maintaining optimal pellet conditions in the bubble column bioreactor.

• Journal of Life Science
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• v.25 no.6
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• pp.673-679
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• 2015

The culture conditions needed to maximize the production of laccase from Pholiota highlandensis mycelia were investigated. Among the tested media for laccase production, Coriolus versicolor medium (CVM; 2% dextrose, 0.4% peptone, 0.6% yeast extract, 0.046% KH₂PO₄, 0.1% K₂HPO₄, 0.05% MgSO₄·7H₂O) showed the highest activity for the enzyme. Then, to optimize culture conditions for laccase activity, the influences of various carbon, nitrogen, phosphorus, and inorganic salt sources in CVM were investigated. The optimum culture medium was 2% fructose, 0.4% peptone with 0.6% yeast extract, 0.05% NaH₂PO₄, and 0.05% MgSO₄·7H₂O as carbon, nitrogen, phosphorus, and inorganic salt sources, respectively. Several aromatic compounds in the medium enhanced laccase activity to varying degrees. Guaiacol induced maximum laccase production, yielding 114.1 U/ml laccase activity after cultivation for 11 days at 25℃. The optimum pH and temperature for laccase production were 8.0 and 35℃, respectively. Native polyacrylamide-gel electrophoresis (PAGE) followed by laccase-activity staining with 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) as the substrate was performed to identify the presence of laccase under the optimum conditions studied. Zymogram analysis of the supernatant culture showed an enzymatic band with a molecular mass of about 90 kDa.

• Current Research on Agriculture and Life Sciences
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• v.14
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• pp.101-110
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• 1996

Using response surface methodology(RSM), the various conditions(agitation speed, air flow, glucose concentration) in jar fermentor culture were investigated to find the optimum conditions for maximum enzyme production. Central-composite-design was used to control the variable constant in the experiment. The glucose isomerase production of Steptomyces chibaensis J-59 was mostly affected by the air flow rate and glucose concentration. The estimated optimum conditions were as follows: 1% birchwood xylan, 1.5% CSL, 0.1% $MgSO_4{\cdot}7H_2O$, 0.012% $CoCl_2{\cdot}6H_2O$, pH 7.0; air flow, 2.2vvm; agitation speed, 587rpm; glucose concentration, 0.586%. Experimental values(7.43GIU/ml) for the enzyme production obtained from the given optimum conditions had a almost resemblane to response values(7.67GIU/ml) predicted by the RSM. The jar fermentor culture by the RSM produced xylose isomerase about 2.7 times as much as the baffled flask culture.

• Mycobiology
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• v.35 no.2
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• pp.82-86
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• 2007

Ergone, a fungal metabolite derived from ergosterol, was previously isolated and identified from Polyporus umbellatus. Ergone is a major component of P. umbellatus known to have anti-aldosteronic diuretic effect and also displays cytotoxic activities. Most of mushroom's fruit bodies used for test contained less than 10 ${\mu}g/g$ of ergone. But P. umbellatus have larger amount of ergone than any other mushrooms. In order to improve the ergone production from the submerged culture of P. umbellatus, several factors including medium composition, culture conditions (temperature and pH) and different combinations of co-cultivation with various mycelia were studied. Among various carbon sources examined, starch proved to be most effective for the production of mycelia. The optimum pH and temperature for a flask culture of P. umbellatus mycelia were found to be 4.5 and $25^{\circ}C$, respectively. Under the optimized culture conditions, both the ergone production (86.9 ${\mu}g/g$) and mycelial growth (3.5 g/l) increased when P. umbellatus was cultured with Armillariella mellea. When the optimized conditions were applied, both mycelium and ergone production were significantly enhanced.