• Biotechnology and Bioprocess Engineering:BBE
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• 제10권1호
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• pp.73-77
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• 2005

Plant-derived natural products have been and will continue to be valuable sources. Elicitors have been employed to modify cell metabolism in order to enhance the productivity of useful metabolites in plant cell/tissue cultures. In this study, several elicitors were used to improve the productivity of useful metabolites and to reduce culture time for archiving high concentration in P. ginseng hairy root cultures. The addition of chitosan, chitosan oligosaccharide and alginate oligosaccharide to the culture of P. ginseng hairy roots caused growth to be inhibited with the increase in elicitor concentration. The usage of the chitosan elicitor and D-glucosamine caused a slight decrease in hairy root growth, whereas total ginseng saponin accumulated slightly with the increase in elicitor concentration. When gel beads were added to the culture medium at the initial period, hairy root growth was enhanced. The maximum growth was 1.35 times higher than that of the control at $1\%$ (w/v). Total ginseng saponin content decreased due to the addition of alginate beads. This would result in consistent diffusion of lower levels of calcium ions during the culture period that promotes biomass growth.

• Journal of Microbiology and Biotechnology
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• 제25권4호
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• pp.452-458
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• 2015

The biocatalytic efficiency of recombinant Corynebacterium glutamicum ATCC 13032 expressing the secondary alcohol dehydrogenase of Micrococcus luteus NCTC2665 was studied. Recombinant C. glutamicum converts ricinoleic acid to a product, identified by gas chromatography/mass spectrometry as 12-ketooleic acid (12-oxo-cis-9-octadecenoic acid). The effects of pH, reaction temperature, and non-ionic detergent on recombinant C. glutamiucm whole cell bioconversion were examined. The determined optimal conditions for production of 12-ketooleic acid are pH 8.0, 35℃, and 0.05 g/l Tween80. Under these conditions, recombinant C. glutamicum produces 3.3 mM 12-ketooleic acid, with a 72% (mol/mol) maximum conversion yield, and 1.1 g/l/h volumetric productivity in 2 h; and 3.9 mM 12-ketooleic acid, with a 74% (mol/mol) maximum conversion yield, and 0.69 g/l/h maximum volumetric productivity in 4 h of fermentation. This study constitutes the first report of significant production of 12-ketooleic acid using a recombinant Corynebacterium glutamicum-based biocatalyst.

• KSBB Journal
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• 제9권2호
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• pp.180-185
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• 1994

본 연구에서는 캘리포니아 양귀비(Eschscholtzia californica) 세포를 airlift 배양기에 적용 배양할 때 shake flask 배양보다 benzophenanthridine alkaloid의 생산성이 감소하는 원인을 찾고 이를 극복하기 위한 실험을 수행하였다. Alkaloid 생산성 감소의 주된 원인은 air sparging에 의해 $CO_2$ 및 ethylene과 같은 유용 성분의 gas가 stripping 되는 것으로 나타났으며 이 stripping 되는 gas를 다시 공급하는 gas recycle 식 airlift 배양기를 개발하였다. 이 배양기에 캘리포니아 양귀비 세포를 배양한 결과 alkaloid 함량이 일반 airlift 배양기 운전 결과보다 약 2.7배 증가하였다. 또한 이 배양기의 gas reservoir의 용량 변화에 따라 alkaloid의 생산성 및 이산화탄소의 농도가 영향을 받음을 확인하였다.

• The Korean Journal of Ecology
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• 제19권4호
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• pp.305-320
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• 1996

It is necessary to obtain information about the productivity of the human-influenced forest and to understand the consumption of biomass resources in secondary forest in order to examine the resource flux by human activity in rural landscape. Thus the aims of this study were to elucidate the biomass and their use of secondary Pinus densiflora forests and to discuss sustainable utilization of secondary forests in rural landscape system. This study was carried out in Yanghwa-ri, Kongjugun, Chungcheongnam-do, central Korea. The changes of growth rate and aboveground biomass of a pine forest for 2 years were analyzed to understand forest management regimes in rural pine forests. Through allometric equations deduced from 25 sample trees, biomass was estimated. The biomass increase of pine forest was approximately 16.36 t/ha/yr in the unexploited stand and 12.24 t/ha/yr in the exploited stand. These were nearly equal to those of natural pine forests in central Korea. This result proved that human-influenced pine forest in rural landscape as well as the natural one has high potentiality to provide forest products. Making graveyard in forest-land was the important disturbance and land-use which currently occurring in rural landscape in the study area. Finally, we presented some forest management for stutainable and positive uses of secondary forests as one of the local energy resources in terms of the holistic landscape-ecological view.

• Plant Biotechnology Reports
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• 제5권1호
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• pp.1-7
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• 2011

Secondary walls have recently drawn research interest as a primary source of sugars for liquid biofuel production. Secondary walls are composed of a complex mixture of the structural polymers cellulose, hemicellulose, and lignin. A matrix of hemicellulose and lignin surrounds the cellulose component of the plant's cell wall in order to protect the cell from enzymatic attacks. Such resistance, along with the variability seen in the proportions of the major components of the mixture, presents process design and operating challenges to the bioconversion of lignocellulosic biomass to fuel. Expanding bioenergy production to the commercial scale will require a significant improvement in the growth of feedstock as well as in its quality. Plant biotechnology offers an efficient means to create "targeted" changes in the chemical and physical properties of the resulting biomass through pathway-specific manipulation of metabolisms. The successful use of the genetic engineering approach largely depends on the development of two enabling tools: (1) the discovery of regulatory genes involved in key pathways that determine the quantity and quality of the biomass, and (2) utility promoters that can drive the expression of the introduced genes in a highly controlled manner spatially and/or temporally. In this review, we summarize the current understanding of the transcriptional regulatory network that controls secondary wall biosynthesis and discuss experimental approaches to developing-xylem-specific utility promoters.

• 노동경제논집
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• 제19권2호
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• pp.161-174
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• 1996

Much of the dual labor markets literature is devoted to exploring the reasons as th why the markets are segmented along the lines where the observed wage differentials are not a result of underlying skill differentials . ; and why otherwise comparable workers different the duration of their job tenure and incidence of unemployment. the logic of competitive economics denies the possibility of equally skilled workers being treated differently in labor markets. The model presented in this paper shows that workers could be segregated quite simply due to the structure of information and job-match quality, even though they are the same in terms of productivity. In general, the model predicts that observability of a worker's productivity and the extent of match specificity are key features of labor market segmentation. An important implication is that the negative from the past labor market experienes, sometimes called as hysteresis effect, helps to restrict mobility of workers among different sectors and results in perpetuation of unemployment in the secondary sector. The model also provides an explanation of the efficient wage scheme in the primary sector.

• 한국환경과학회지
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• 제8권1호
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• pp.101-106
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• 1999

The relationship between primary productivity and changes in water quality was investigated at Mulgum station, a site downstream of the Nakdong River, Korea. Phytoplankton production was characterized by blooms of Microcystis aeruginosa during the summer and Stephanodiscus hantzschii during the winter. Primary production and secondary production by bacterioplankton ranged from 1.5~53.5 mg-C/ι day and 0.1~0.3 mg-C/ι day, respectively. Distribution of total organic carbon appeared to be highly correlated with phytoplankton biomass, especially during blooms of M. aeruginosa, when particulate organic carbon was 81% of total organic carbon and the main source of organic materials supplied into the water. The correlation coefficient between chlorophyll-a and BOD was 0.86. Thus it was concluded that autochthonous phytoplankton mostly affected the BOD level. Total bacterial numbers were also highly correlated with chlorophyll-a ($r^2$= 0.84) and the bacterial community appears to be regulated by phytoplankton biomass in this area.

• 동아시아경상학회지
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• 제5권2호
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• pp.48-54
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• 2017

Public holidays are periods set aside by nations or states to observe particular events like national days, independence anniversary or religious festivals. These days are different from the usual periods of statutory leave or vacation provided for workers in the collective agreement or rule of engagement at the point of entry. These periods of leave enjoyed by workers include annual vacation, casual leave, sick leave, maternity leave, paternity leave and others as may be recognized within an establishment. Individual worker's period of leave is personal and at the discretion of the worker or the organization as the case may be, but public holidays involve the stoppage of work by the entire workforce within the period it would last. Nigeria observes many public holidays some of which, at times, are unplanned for by the people. This has attracted arguments for and against on the basis that these holidays are too many and detrimental to productivity and the national economy. Using secondary data, this paper examines the issue and opines that there is the need to review these public holidays with a view to halting their negative effects on the nation's economy. Also, measures to manage these holidays in line with constitutional provisions are espoused.

• Applied Biological Chemistry
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• 제48권1호
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• pp.1-15
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• 2005

농작물이 병해충 및 잡초 등에 의하여 피해를 받게 되면 농업생산성은 상당히 저하된다. 따라서 농업생산성을 높이기 위하여 합성농약을 과용해 왔고, 이로 인하여 토양의 질과 농업환경이 파괴되는 결과를 초래하고 있어서 지속적인 농업이 점차 어려워지고 있다. 오늘날의 농업은 농업환경의 파괴를 최소화하고 농산물의 안전성을 확보함과 동시에 생산성을 증대해야하는 복합적인 문제에 직면해 있다. 한편, 식물은 일반적으로 생존하기 위하며 외부의 침입으로부터 자신을 보호하거나 자신의 영역을 확보하기 위하며 다양한 종류의 2차대사물질을 생산하고 방출한다. 병원균이 침입했을 때 식물이 생산하는 항생물질인 phytoalexin으로는 화본과 식물의 경우 flavonoid계와 diterpenoid계의 물질을 생성하고, 쌍자엽 식물은 감염된 병원균의 종류에 상관없이 Leguminosae과는 flavonoids계, Cruciferae과는 indole 유도체, Solanaceae과는 sesquiterpenoid계, Umbelliferae과는 coumarin계 물질들을 생성하여 병원균에 저항성을 가진다. 곤충의 생리작용을 저해하거나 섭생을 싫어하게 하는 기능의 물질로는 terpene계의 pyrethrin, azadirachtin, limonin, cedrelanoid, toosendanin, fraxinellone/dictamnine 등이 있으며, alkaloid계로서는 terpenoid와 alkaloid가 결합된 sesquiterpene pyridine 및 norditerpenoids alkaloids와 azepine계, amide계, loline계, stemofoline계, pyrrolizidine계 alkaloids 등이 있다. 식물은 또한 자신의 영역을 확보하기 위하여 다른 식물의 생장을 저해하는 물질을 생성하는데 여기에는 terpene계의 essential oil 및 sesquiterpene lactone과 이외에 benzoxazinoids, glucosinolate, quassinoid, cyanogenic glycoside, saponin, sorgolennone, juglone 등 다수의 2차 대사물질들이 있다. 이와 같은 기능의 2차 대사물질을 병해충 및 잡초 방제에 직, 간접으로 이용하는 것은 친환경농업의 한 가지 방법일 수 있다. 그러나 천연물질들은 자연계에서 쉽게 분해되어 효율이 떨어지는 경우가 많고 식물을 통하여 생산하는데도 한계가 있다. 따라서 보다 안전성과 효율성이 뛰어난 2차 대사물질을 찾아내는 연구와 아울러 방제기능이 있는 물질의 생합성경로를 구명하고 대사공학적으로 이용하므로 병해충에 저항성이 있고 잡초 방제효과를 갖는 형질전환 식물을 육성하는 연구가 지속적으로 이루어져야 할 것이다.

• 한국연소학회:학술대회논문집
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• 한국연소학회 2014년도 제49회 KOSCO SYMPOSIUM 초록집
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• pp.339-342
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• 2014

Rotary kiln produces lime from limestone through thermal decomposition. Ring formation in kiln internal wall is known issue that decreases productivity. The cause of ring formation is temperature imbalance as flame leans toward upper wall. Therefore, burner nozzle geometry was changed to improve air-fuel mixing state which leads to prevention of ring formation. CFD simulation and experimental test were performed in this study to investigate the effect of air-fuel mixing on flame structure, temperature and $NO_X$ concentration. It is shown that combustion efficiency has been enhanced and $NO_X$ concentration has been decreased by using swirl flow for secondary combustion air. It's also shown that flame has been straightened by using straight flow for secondary combustion air.