• 한국토양비료학회지
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• 제43권6호
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• pp.978-980
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• 2010

This study was conducted to observe the cause of injury of fig plant. Nitrogen dioxide gas can be evolved at low pH or reduced in soil. Fig plant cultivated with nutrient solution was wilted or withered. Injury symptom for nutrient solution containing nitrous acid was worse as pH of soil decreased. However, increase in pH of nutrient solution treated with increasing $Ca(OH)_2$ solution prevented nutrient solution from producing nitrogen dioxide gas. Recovery of the fig plant by pH increase indicated that the cause of injury was nitrogen dioxide gas.

• 한국토양비료학회지
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• 제45권6호
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• pp.925-927
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• 2012

산성화된 토양에서 생육하는 오이가 황백화 되면서 시드는 증상이 발생하여 현장에서 토양을 검사하여 진단하고 현장에서 토양 pH를 측정한 결과 4.2로 매우 낮은 강산성이었고, 실험실에서 분석한 결과 4.5로 나타났다. 토양을 풍건하여 토양 pH를 측정한 결과 4.5로 강산성이었다. 그래서 토양을 포화추출법으로 용액을 채취하여 분석한 결과 Al이 해리되어 나오고 있었고 식물체를 분석한 결과 Al이 고농도로 흡수되어 있었으며 질소와 Ca의 함량이 매우 낮았다. 현장에서 pH를 교정하기 위하여 소석회 포화액과 탄산칼슘을 처리한 결과 pH를 6.5로 조절할 수 있는 소석회 450 mL $plant^{-1}$를 처리한 주에서 어린 잎부터 정상적인 생육을 하였다. 이 결과로부터 강한 산성토양에서 나타난 오이의 황백화 증상은 Al이 해리되어 식물체로 과잉 흡수되고 이로 인하여 질소와 칼슘의 부족으로 야기된 것으로 나타났다.

• Journal of Microbiology and Biotechnology
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• 제28권1호
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• pp.95-104
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• 2018

Biosurfactants or microbial surfactants are surface-active biomolecules that are produced by a variety of microorganisms. Biodegradability and low toxicity have led to the intensification of scientific studies on a wide range of industrial applications for biosurfactants in the field of environmental bioremediation as well as the petroleum industry and enhanced oil recovery. However, the major issues in biosurfactant production are high production cost and low yield. Improving the bioindustrial production processes relies on many strategies, such as the use of cheap raw materials, the optimization of medium-culture conditions, and selecting hyperproducing strains. The present work aims to obtain a mutant with higher biosurfactant production through applying mutagenesis on Bacillus subtilis SPB1 using a combination of UV irradiation and nitrous acid treatment. Following mutagenesis and screening on blood agar and subsequent formation of halos, the mutated strains were examined for emulsifying activity of their culture broth. A mutant designated B. subtilis M2 was selected as it produced biosurfactant at twice higher concentration than the parent strain. The potential of this biosurfactant for industrial uses was shown by studying its stability to environmental stresses such as pH and temperature and its applicability in the oil recovery process. It was practically stable at high temperature and at a wide range of pH, and it recovered above 90% of motor oil adsorbed to a sand sample.