• KSBB Journal
• /
• 제15권5호
• /
• pp.444-451
• /
• 2000

Nonliving methanotrophic biomass was used as biosorbent to remove lead which is one of representative pollutants in metal-bearing wastewater. Solution pH, maximum uptake, biosorbent dose and ionic strength were considered as major factors for adsorption experiments. The optimum pH range for lead removal was increased 3.8∼11.0 for methanotrophic biomass compared to biosorbent-free control, pH of 8.4∼11.2. Removal efficiency of lead by methanotrophic biomass was pH dependent, but less sensitive than that of control. In isotherm experiments with 0.2g biosorbent/L at initial solution pH 5.0, methanotrophic biomass took up lead from aqueous solutions to the extent of 1085 mg/g biomass. Removal amount of lead increased with an increase of biomass dose. According to biomass dose for initial 1000 mg Pb/L at initial pH 5.0, the optimum amount of biomass for maximum lead removal per unit methanotrophic biomass was 0.2 g biomass/L. As a result of scanning electron microscope (SEM) micrographs equipped with energy dispersive spectroscopy (EDS), lead removal by methanotrophic biomass seemed to be through adsorptions on the surface of methanotrophic biomass and exopolymers around the biomass. EDS spectra confirmed that lead adsorption appeared on the biomass and exopolymers that may be effective to lead removal comparing before and after contact with lead. Removal efficiency of lead was slightly affected by ionic strength up to 2.0 M of NaCl and NaNO$_3$respectively.

• 한국환경보건학회지
• /
• 제33권2호
• /
• pp.150-157
• /
• 2007

The chemical and photochemical decolorization of Rhodamine B (RhB) in water has been carried out by Fenton, Fenton-like and photo-Fenton-like process. The effect of applied $H_2O_2,\;Fe^{2+}$ dosage (Fenton process), $H_2O_2,\;Fe^{\circ}$ dosage (Fenton-like and photo-Fenton-like process), UV light power (photo-Fenton-like process) pH (all processes) have been studied. The results obtained showed that more than 98% of color removal was obtained for the RhB solutions in every process. However, Fenton-like process was not suitable for the color removal of RhB because Fenton-like process was required much more reagents than Fenton and photo-Fenton-like process. The Fenton and photo-Fenton-like process showed similar reagents need. Optimum pH for three processes in this study is about pH 3. The relative order of sensitivity for pH of each process was: Fenton-like > photo-Fenton-like > Fenton.

• 상하수도학회지
• /
• 제28권2호
• /
• pp.207-215
• /
• 2014

Wastewater containing heavy metals such as copper (Cu) and nickel (Ni) is harmful to humans and the environment due to its high toxicity. Crystallization in a fluidized bed reactor (FBR) has recently received significant attention for heavy metal removal and recovery. It is necessary to find optimum reaction conditions to enhance crystallization efficacy. In this study, the effects of crystallization reagent and pH were investigated to maximize crystallization efficacy of Cu-S and Ni-S in a FBR. CaS and $Na_2S{\cdot}9H_2O$ were used as crystallization reagent, and pH were varied in the range of 1 to 7. Additionally, each optimum crystallization condition for Cu and Ni were sequentially employed in two FBRs for their selective removal from the mixture of Cu and Ni. As major results, the crystallization of Cu was most effective in the range of pH 1-2 for both CaS and $Na_2S{\cdot}9H_2O$ reagents. At pH 1, Cu was completely removed within five minutes. Ni showed a superior reactivity with S in $Na_2S{\cdot}9H_2O$ compared to that in CaS at pH 7. When applying each optimum crystallization condition sequentially, only Cu was firstly crystallized at pH 1 with CaS, and then, in the second FBR, the residual Ni was completely removed at pH 7 with $Na_2S{\cdot}9H_2O$. Each crystal recovered from two different FBRs was mainly composed of CuxSy and NiS, respectively. Our results revealed that Cu and Ni can be selectively recovered as reusable resources from the mixture by controlling pH and choosing crystallization reagent accordingly.

• ALGAE
• /
• 제21권3호
• /
• pp.317-321
• /
• 2006

The effects pH and salinity on the brown alga Sargassum fulvellum were investigated in the context of the removal of two major associated animals, Caprella scaura and Gammaropsis utinomi. Optimum quantum yield (Fv/Fm) of S. fulvellum was also examined in the same experimental conditions as an index of stress. Experiments on pH and salinity tolerances of the two animal species indicated that mortality was more than 80% at extremes of pH (2, 3, 4, 10, 11, 12) and salinity (0, 3.5, 7, 10, 44 psu) after a 5 min treatment. Lethal time (LT50) from pH 2 to pH 4 was less than 90 sec in C. scaura, and less than 70 sec in G. utinomi. From 0 to 10 psu, LT50 was less than 20 sec in C. scaura and less than 60 sec in G. utinomi. The quantum yield of S. fulvellum was not significantly different from controls within the pH range 4~10, and within the salinity range of 7-40 psu. When exposed to pH and salinity conditions outside these ranges, the effect of these factors on the removal of two animal species was higher, but quantum yield was highly reduced. These results indicate that the optimal conditions for removing the animal species without affecting optimum quantum yield were pH 4-10, and salinities 7-10 psu and 44 psu.

• KSBB Journal
• /
• 제17권1호
• /
• pp.14-19
• /
• 2002

본 연구의 목적은 회전생물반응기에 고정화한 P. chrysosporium IFO 31249를 이용하여 LiP 생산의 최적 조건을 조사하는 것이다. 회전생물반응기에서 batch culture시 최대 LiP 활성도는 300 U/L이었다. LiP 생산의 최적 조건은 드림의 회전 속도는 1 rpm, 담체 충진율은 20%이었다. MnP 생산을 위한 $MnSO_4$$\cdot$$H_2O$ 의 최적 농도는 50 ppm이었다. 그리고 산소의 충분한 공급은 LiP 생산의 가장 중요한 인자이었다. 또한 LiP 및 MnP의 생산에 있어 repeated-batch culture가 3번이나 가능하였다.

• Communications for Statistical Applications and Methods
• /
• 제8권1호
• /
• pp.147-151
• /
• 2001

In discrete red and black, you can stake any amount s in your possession, but the value of s takes positive integer value. Suppose your goal is N and your current fortune is f, with 0$\frac{1}{2}$ where the house has the advantage over the player, and with the value of p greater than $\frac{1}{2}$ where the player has the advantage over the house. The optimum strategy at any f when p<$\frac{1}{2}$ is to play boldly, which is to bet as much as you can. The optimum strategy when p>$\frac{1}{2}$ is to bet 1 all the time.

• Mycobiology
• /
• 제35권3호
• /
• pp.135-144
• /
• 2007

The removal efficiency of the heavy metals Zn, Pb and Cd by the zoosporic fungal species Saprolegnia delica and the terrestrial fungus Trichoderma viride, isolated from polluted water drainages in the Delta of Nile in Egypt, as affected by various ranges of pH values and different temperature degrees, was extensively investigated. The maximum removal efficiency of S. delica for Zn(II) and Cd(II) was obtained at pH 8 and for Pb(II) was at pH 6 whilst the removal efficiency of T. viride was found to be optimum at pH 6 for the three applied heavy metals. Regardless the median lethal doses of the three heavy metals, Zn recorded the highest bioaccumulation potency by S. delica at all pH values except at pH 4, followed by Pb whereas Cd showed the lowest removal potency by the fungal species and vice versa in case of T. viride. The optimum bio-mass dry weight production by S. delica was found when the fungus was grown in the medium treated with the heavy metal Pb at pH 6, followed by Zn at pH 8 and Cd at pH 8. The optimum biomass dry weight yield by T. viride amended with Zn, Pb and Cd was obtained at pH 6 for the three heavy metals with the maximum value at Zn. The highest yield of biomass dry weight was found when T. viride treated with Cd at all different pH values followed by Pb whilst Zn output was the lowest and this result was reversed in case of S. delica. The maximum removal efficiency and the biomass dry weight production for the three tested heavy metals was obtained at the incubation temperature $20^{\circ}C$ in case of S. delica while it was $25^{\circ}C$ for T. viride. Incubation of T. viride at higher temperatures ($30^{\circ}C\;and\;35^{\circ}C$) enhanced the removal efficiency of Pb and Cd than low temperatures ($15^{\circ}C\;and\;20^{\circ}C$) and vice versa in case of Zn removal. At all tested incubation temperatures, the maximum yield of biomass dry weight was attained at Zn treatment by the two tested fungal species. The bioaccumulation potency of S. delica for Zn was higher than that for Pb at all temperature degrees of incubation and Cd bioaccumulation was the lowest whereas T. viride showed the highest removal efficiency for Pb followed by Cd and Zn was the minor of the heavy metals.

• Applied Biological Chemistry
• /
• 제10권
• /
• pp.23-31
• /
• 1968

Chaetomium globosum의 Cellulase 생산(生産)과 조효소(粗酵素)의 성질(性質)은 시험(試驗)한바 다음의 결과(結果)를 얻었다. 1. 효소생성배양(酵素生成培養)은 맥피고체배양(麥皮古體培養)이 다른 어떤 액체(液體) 혹(或)은 진탕배양보다 좋은 결과(結果)를 나타낸다. 2. 효소생산(酵素生産)은 $8{\sim}10$일(日)이 최고(最高)이며 그 후(後)는 감소(減少)된다. 3. 환원당(還元糖) 측정(測定)에 의(依)한 Cellulase 활성(活性) 측정법(測定法)으로 최적(最適) pH, 최적(最適) 온도(溫度), pH 안전(安全) 및 열안전(熱安全)은 다음 같다. (1) 조효소(粗酵素)의 최적(最適) pH는 $4.0{\sim}4.5$이다. (2) 조효소(粗酵素)의 최적(最適) 온도(溫度)는 $40^{\circ}C$이다. (3) 조효소(粗酵素)의 안전(安全) pH는 $.3.5{\sim}6.5$이다. (4) 조효소(粗酵素)의 열안전(熱安全)은 $50^{\circ}C$ 이하(以下)이다. 4. 투석조효소(透析粗酵素)는 $Mn^{2+},\;Mg^{2+},\;Fe^{2+},o^{2+}$에 상당(相當)히 부활(賦活)되며 $Hg^{2+}$은 현저히 저해(沮害)된다.

• 한국수산과학회지
• /
• 제27권6호
• /
• pp.704-711
• /
• 1994

고등어 아가미에서 추출한 리폭시게나아제는 에이코사펜타엔산에 대해서 활성이 가장 높았으며, 그 다음으로 아라키돈산, 리놀산순으로 활성을 나타내었다. 적정 pH는 에이코사펜타엔산, 아라키돈산, 리놀산에 대하여 각각 pH 4.5, 5.0, 4.8이었다. 또한 이 효소는 모든 기질에 대하여 pH 5.5에서 가장 안정하였다. 적정온도는 기질의 종류에 상관없이 $25^{\circ}C$였으며, 리놀산, 아라키돈산의 경우 $8^{\circ}C$에서 열안정성이 가장 높았다. 반면, 에이코사펜타엔산의 경우, $20^{\circ}C$에서 안정성이 가장 높았다. 적정이온강도는 모든 기질에 대하여 0.22M이었다. $Sn^{2+}$, vitamin E, catechin은 1.0mM에서 이 효소의 활성을 완전히 저해시켰다. 이 효소의 분자량은 42,000달톤이었다.

• Journal of Microbiology and Biotechnology
• /
• 제24권6호
• /
• pp.781-787
• /
• 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.