• Korean Journal of Microbiology
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• v.51 no.1
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• pp.75-80
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• 2015

Pseudoalteromonas donghaensis HJ51, isolated from the East Sea, has been reported as a novel strain to produce extracellular protease. Crude supernatant was used to determine optimal activity and optimal production conditions for the enzyme. It was found that the optimal temperature and pH of the protease were $40^{\circ}C$ and pH 7.5-10.5, respectively. The enzyme activity was kept to 88% at the pH 11. In metal requirement analysis, the enzyme exhibited the highest activity when 10 mM $Fe^{3+}$ was supplied. While supplementation of additional carbon sources used in study showed no positive effect on cell growth and enzyme activity, the addition of beef extract, tryptone, or casamino acids instead of peptone of PY-ASW containing 1% glucose increased enzyme production to 21, 7, 4%, respectively. Taken together these properties, the enzyme produced from P. donghaensis HJ51 can be applied to the industries that require protease activity under alkaline pH and low temperature.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2001.09a
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• pp.160-163
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• 2001

본 연구에서는 Fe$^{0}$ /$H_2O$$_2$ 시스템을 이용하여 디젤 오염토양의 산화처리효율과 경제성 향상을 위한 실험을 수행하였다. 앞선 연구결과에서 최적 pH조건은 3이었으며, 과산화수소와 철 분말의 양은 비례적으로 증가할수록 처리효율이 높게 나타났다. 1) 이번 연구에서는 pH조절에 따른 처리효율의 향상효과를 알아보기 위해 pH 값을 3으로 일정하게 유지하여 반응을 수행하였으며, 일정 철 분말 농도조건에서 과산화수소의 주입방법에 따른 반응변화를 살펴보기 위해 과산화수소를 여러 비율로 분할 주입하면서 실험을 실시하였다. 본 연구결과에 따르면 pH를 3으로 일정하게 유지함으로써 초기에만 pH를 3으로 조정한 이전의 연구에서 반응이 경과함에 따라 나타나는 pH상승에 따른 처리효율의 감소 효과를 줄며 전체적인 TPH 처리효율을 10%이상 높일 수 있었으며, 같은 양의 TPH 제거에 소모되는 과산화수소의 양을 20% 정도 줄일 수 있었다. 과산화수소의 분할주입에 따른 반응향상효과 실험에서는 5회에 걸쳐 분할 주입한 경우에 3시간 이후 경미한 반응성 향상효과를 얻을 수 있었다. 이러한 결과는 과산화수소를 분할하여 주입함으로써 한번에 주입한 경우에 비하여 유기물의 산화에 직접적으로 참여하지 않는 과산화수소의 scavenging 효과를 최소화할 수 있음을 보여주는 것이다. 따라서 최적 pH의 일정 유지와 과산화수소의 분할주입으로 철 분말을 이용한 펜톤유사반응의 처리효율과 경제성 제고 모두에 있어서 효과가 있음을 알 수 있었다.

• Journal of Korean Society of Environmental Engineers
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• v.38 no.5
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• pp.228-235
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• 2016

Nitrite accumulation is essential for constructing an anammox process. As the pH in the reactor exerts a complicated and strong influence on the reaction rate, we investigated its effects upon treatment of an ammonic wastewater (2,000 mgN/L) through modeling and experiment. The modeling results indicated that the reaction stability is strongly affected by pH, which results in a severe reduction of the 'stable region' of operation under alkaline environments. On a coordinate of the total ammonia nitrogen (TAN) concentration vs. pH, the maximal stable reaction rates and the maximal nitrite accumulation potentials could be found on the 'stability ridge' that separates the stable region from the unstable region. We achieved a stable and high ammonia oxidation rate (${\sim}6kgN/m^3-d$) with a nitrite accumulation ratio of ~99% when operated near the 'stability ridge'. The optimum pH that can be observed in experiments varies with the TAN concentrations utilized, although the intrinsic optimum pH is fixed. The direction of change is that the optimum operational pH falls as the TAN concentration increases, which is in excellent accordance with the observations in the literature. The optimum operational pH for 95% nitritation was predicted to be ~8.0, whereas it was ~7.2 for 55% partial nitritation to produce an anammox feed in our experimental conditions.

• Journal of the Korean Society of Food Science and Nutrition
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• v.43 no.9
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• pp.1462-1466
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• 2014

In this study, an attempt was made to produce oat protein concentrates from defatted oat groat by alkali extraction. Independent variables formulated by D-optimal design were NaOH concentration (X1, 0.005~0.06 N) for extraction and precipitation pH (X2, pH 4.0~6.0), and the dependent variable was extraction yield (Y1, %). Experimental results were analyzed by response surface methodology to determine optimized extraction conditions. Extraction yield increased both with an increase in NaOH concentration of the extraction solution and when approaching a precipitation pH of 4.9, and NaOH concentrations were a major influencing parameter. Solubility of oat protein concentrates showed a minimum value (i.e., 0.1%) at pH 5 and increased substantially at pH values in the range of ${\leq}$ pH 3 or ${\geq}$ pH 7, reaching a maximum value at pH 11 (i.e., 76%). Regression equation coincided well with the results of the experiment. Optimized extraction conditions to maximize extraction yield were 0.06 N NaOH (X1) for extraction and pH 4.7 (X2) for precipitation.

• Tunnel and Underground Space
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• v.26 no.3
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• pp.154-165
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• 2016

This paper presents experimental results to investigate the affects of acidic solution under loading condition on rock properties. In the experiment, the variations of various rock properties including effective porosity, thermal conductivity, and etc were investigated with different pHs of solution and magnitudes of loading. The results show that the rock property change was increased with low pH under loading. It was predicted that chemical reaction rate would be increased in low pH. Below the crack initiation stress of the rock specimen, the variation of rock property change was reduced with increased loading. It could be explained with the reduced chemical reaction area by the compressional loading if there is no crack generation.

• Microbiology and Biotechnology Letters
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• v.17 no.2
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• pp.148-153
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• 1989

A strain of alkalophilic Bacillus sp. YC-335 has been isolated from soil. The strain was capable of producing large amount of cyclodextrin glycosyl transferase (CGTase) in the culture broth. The preferable medium composition has been determined to be as follows : 1.5% soluble starch, 5% corn steep liquor, 0.1% $K_2$HPO$_4$, 0.02%mgSO$_4$.7$H_2O$, 1% CaCO$_3$and 1% Na$_2$CO$_3$(pH 10.3). The highest enzyme production was observed after 48 hours of cultivation at 31$^{\circ}C$. The optimum pH and temperature for the activity of crude enzyme were 6.0 and 5$0^{\circ}C$, respectively. The enzyme was stable between pH 5 and 9, and upto 5$0^{\circ}C$. The enzyme converted starch into $\alpha$-, $\beta$- and ${\gamma}$-CD in the relative amounts of 1:10:1.5, respectively.

• Journal of Food Hygiene and Safety
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• v.15 no.2
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• pp.144-150
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• 2000

The present study was peformed to determine the hydrolysis rate constants and degradation products of phosphamidon and proffnofos by the OECD method. Hydrolysis rate constants of phosphamidon in pH 4, pH 7, and pH 9 buffer solutions at 25 and 40$^{\circ}$C were 0.0020, 0.0022, 0.0049 and 0.0040, 0.0050, 0.0150, respectively. Hydrolysis rate of phosphamidon was accelerated by temprerature change under same pH conditions, and half-life of phosphamidon in pH 9 at 40。C was 3 times faster than that at 25。C. Hydrolysis rate of phosphamidon in alkaline solution(pH 9) was 2~4 times faster than that in acidic solution(pH 4) and neutral solution(pH 7) under same temperature. Hydrolysis rate constants of profenofos in pH 4, pH 7, and pH 9 buffer solutions at 25 and 40。C were 0.0022, 0.0047, 0.0860 and 0.0035, 0.0086, 0.1245, respectively. Hydrolysis rate of profenofos was accelerated by temprerature change under same pH conditions. Hydrolysis rate of profenofos in alkaline solution(pH 9) was 15~40 times faster than in acidic solution(pH 4) and neutral solution(pH 7) under same temperature condition, and half-life of profenofos was very fast within 8 hours. The hydrolysis rate of profenofos was faster than that of phosphamidon. In order to identify hydrolysis products, the extracts of degradation products were analyzed by GC/MS. The mass spectra of hydrolysis products of phosphamidon were at m/z 153 and 149, those of the profenofos were at m/z 208 and 240, respectively. The hydrolysis products of phosphamidon were O, O-dimethyl phosphate(DMP) and N, N-diethylchloroacetamide, and those of profenofos were 4-bromo-2-chlorophenol and O-ethyl-S-propyl phosphate.

• Journal of the Korean Ceramic Society
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• v.40 no.6
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• pp.583-588
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• 2003

Cation exchange capacity of clay, white clay and zeolite was measured by the adsorption test for 3 different heavy metal (Cd, Cr, Zn) standard solutions whose concentrations were varied by 10, 20, 30 ppm and pH were varied by 3, 5, 7, 9, respectively. The adsorption rate of Cd and Zn increased with increasing pH and slowly increased with increasing pH above pH 5. However, adsorption rate of Cr did not increase with increasing pH. Especially, Cr adsorption rate of the mixture of clay and white clay at pH 5 showed an half decrease compared to that at pH 3. The adsorption rate of mixed heavy metal solutions was in the order of Cd, Zn > Cr; however, the order was changed by Fe>Pb, Cu>Cr>Zn>Cd in case of Cu, Fe and Pb addition.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2004.04a
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• pp.227-230
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• 2004

본 연구에서는 유류오염토양 세척유출수내 미세토사의 효율적 제거를 위한 최적의 방안 및 적용 운전 조건을 도출하고자 하였다. 응집제를 주입하지 않은 blank 실험결과, 광운대학교 토양 세척유출수는 pH 7～12의 범위에서 65～75%의 효율을 나타내었고, 우이천 하천퇴적 토양 세척유출수는 pH 7～11의 범위에서 30% 안팎의, pH 12에서는 70% 정도의 낮은 효율을 나타내었다. pH 13에서는 두 가지 세척유출수에서 각각 91%, 85%의 효율을 나타내었다. 응집ㆍ침전 실험 결과, 광운대학교 토양 세척유출수는 FeC13, alum, PAC을 적용하였을 때 대체로 99% 이상의 효율을 보였으나, PAM을 적용하였을 때는 pH 13에서만 약 95%의 효율을 보였을 뿐 pH 7～12의 범위에서는 50～70%의 낮은 효율을 보였다. 우이천 하천퇴적 토양 세척유출수는 alum과 PAC을 적용하였을 때 대체로 90% 이상의 효율을 나타내었으나, FeC13와 PAM을 적용하였을 때는 pH 13일 경우에서만 98%이상의 효율을 보였을 뿐 다른 pH조건에서는 대체로 60%이하의 효율을 보였다. 두 가지 세척유출수에 대하여 높은 효율을 보인 alum과 PAC의 경제성을 비교해본 결과 같은 양의 세척유출수를 응집처리 할 경우 PAC에 비하여 alum을 적용하였을 때 적은 비용이 소요되었다. 따라서 alum이 효율성과 경제성에서 가장 우수함을 알 수 있었다.

• Microbiology and Biotechnology Letters
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• v.11 no.1
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• pp.33-38
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• 1983

As flocculent strains are likely to have considerable potential for internal cell recycle, kinetic studies on glucose medium with flocculent Saccharomyces uvarum were carried out in batch and continuous culture. Using a mathematical model, the kinetic parameters at each temperature and pH were estimated in order to establish optimal conditions. It was found that an overall optimum temperature for growth and ethanol production in the range 33-35$^{\circ}C$ was desirable. With regard to the effect of pH, ethanol production by S. uvarum was found to be relatively insensitive to pH value between 4 and 6, with an optimum pH of around 5. At these optimal conditions a maximum ethanol productivity of 12 g/$\ell$/h was determined using semi-batch process together with 5. uvarum.