• Journal of Soil and Groundwater Environment
• /
• v.27 no.1
• /
• pp.25-30
• /
• 2022

Mackinawite (FeS), as a ubiquitous reduced iron mineral, is known as a key controller of redox reactions in anaerobic subsurface environment. The reaction of FeS with redox-sensitive toxic element such as arsenic is substantially affected by pH conditions of the given environments. In this study, the interaction of As(V) with FeS was studied under strict anaerobic conditions with various pH conditions. The pH-dependent arsenic removal tests were conducted under wide ranges of pH conditions and X-ray absorption spectroscopy (XAS) was applied to investigate the reaction mechanisms under pH 5, 7, and 9. The removal efficiency of FeS for As(V) showed the higher removal of As(V) under low pH conditions and its removal efficiency decreased with increasing pH, and no As(V) reduction was observed in 1 g/L FeS solution. However, XAS analysis indicated the reduction of As(V) to As(III) occurred during reaction between FeS and As(V). The reduced form of As(III) was particularly identified as an arsenic sulfide mineral (As₂S₃) in all pH conditions (pH 5, 7, and 9). As₂S₃ precipitation was more pronounced in pH 5 where the solubility of FeS is higher than in other pH conditions. The linear combination fitting results of XAS demonstrated that As(V) removal mechanism is concerted processes of As₂S₃ precipitation and surface complexation of both arsenic species.

• Journal of Environmental Science International
• /
• v.21 no.10
• /
• pp.1255-1263
• /
• 2012

Batch cultivations were performed to evaluate the influences of the initial pH condition on mesophilic and thermophilic acidogenic fermentation with food waste recycling wastewater. In both conditions of mesophilic and thermophilic fermentation, TVFAs production rates were maximized at the initial pH 7 condition as 0.15 and 0.23 g TVFAs/L hr, respectively. And pH was also maintained stably between 6 and 7 during 72hr acidogenic cultivation at both conditions. However, predominant VFA components were different according to reaction temperature conditions. In mesophilic condition, propionic acid which has low conversion efficiency to methane was accumulated up to 1,348 mg/L while acetic and butyric acid were predominant in thermophilic condition. Therefore, thermophilic acidogenic fermentation was superior for the effective VFAs production than mesophilic condition. From the DGGE analysis, the band patterns were different according to the initial pH conditions but the correlations of the each band were increased in similar pH conditions. These results mean that microbial communities were certainly affected by the initial pH condition. Consequently, the adjustment of the initial pH to neutral region and thermophilic operation are needed to enhance acidogenic fermentation of food waste recycling wastewater.

• Food Science and Preservation
• /
• v.30 no.2
• /
• pp.300-310
• /
• 2023

This study was carried out to investigate the effect of the extraction conditions for persimmon (Diospyros kaki Thunb.) leaf tea (PLT) on its color quality and antioxidant properties. The amount of persimmon leaf (PL) powder and pH influenced the PLT's color and antioxidant capacity. As the amount of PL powder in tea increased, lightness decreased while yellowness increased. The PLT with the highest amount of PL (10 mg/mL) exhibited the highest 2,2'-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) radical scavenging activity and ferric reducing antioxidant power (FRAP). In addition, the PLT with the highest PL showed the highest total polyphenol and flavonoid contents. Subsequently, PLT was prepared using 10 mg/mL PL powder under varying pH conditions. As pH increased from 4 to 7, lightness decreased while redness and yellowness increased. Antioxidant capacity was determined using 2,2-diphenyl-1-picrylhydrazyl radical scavenging activity and FRAP assay showed that lower pH exhibited higher antioxidant capacity. The PLT extracted under the lowest pH of 4 showed higher polyphenol and flavonoid contents than that extracted under higher pH conditions. Overall, PLT extraction using a solvent with pH 4.0 showed better antioxidant activities and higher amounts of polyphenolic compounds. Simultaneously, lesser lightness, redness, and yellowness were detected in PLT extracted under pH 4 conditions. In conclusion, to acquire a better functional health benefit in terms of antioxidant capacity, preparing PLT under pH 4 conditions is suggested.

• KSBB Journal
• /
• v.10 no.2
• /
• pp.191-195
• /
• 1995

Using Pseudomonas sp. CH-414, the optimum culture conditions were investigated for the cell growth and the phospholipid production in batch culture by varying pH and aeration rate. With starting the cultivation under the conditions of pH 7.0 and 1vvm, pH was controlled to 6 or 8 at 30 hours of culture time. In the case of changing into pH 6.0, the phospholipid production was increased by ca. 20% with comparison to the case of pH 7.0. However, the biomass and the phospholipld concentration were rapidly decreased after 30 hours of culture time when pH was controlled to 8.0. As the aeration rate was increased, the biomass was increased while the phospholipid concentration was considerably varied and unstable. Especially, the concentration of phospholipid was rapidly decreased with 3vvm of aeration rate. Finally, under the culture conditions of pH 7.0 and 3vvm until 30 hours for the cell growth, which were controlled to pH 6.0 and 1vvm for the stable production of phospholipid beyond that time, the dry cell weight was $18.5g/\ell$ and the phospholipid concentration was $\0.83g/ell$ (45mg/g cell).

• Journal of Microbiology and Biotechnology
• /
• v.32 no.4
• /
• pp.514-521
• /
• 2022

We report the effect of pH on the supramolecular complexation of two biothiols, viz., homocysteine (Hcy) and cysteine (Cys), with cucurbit[7]uril (CB[7]). Under basic pH conditions, Cys did not complex with CB[7], whereas Hcy efficiently complexed with CB[7], as confirmed by ¹H NMR spectroscopy and Ellman's reagent (5,5'-dithio-bis(2-nitrobenzoic acid), DTNB) assay. ¹H NMR and Raman spectroscopic studies revealed that, in the absence of CB[7], Hcy auto-oxidized slowly (~36 h) to homocystine (HSSH) under basic pH conditions. However, the rate of Hcy oxidation increased by up to 150 fold in the presence of CB[7], as suggested by the DTNB assay. Thus, supramolecular complexation under basic pH conditions led to the formation of a HSSH-CB[7] complex, and not Hcy-CB[7]. The results indicate that Hcy is rapidly oxidized to HSSH under the catalysis of CB[7], which acts as a reaction chamber, in basic pH conditions. Our studies suggest that Hcy concentration, a risk factor for cardiovascular disease, can be selectively and more easily quantified by supramolecular complexation with CB [7].

• Journal of Korean Society on Water Environment
• /
• v.27 no.6
• /
• pp.754-759
• /
• 2011

A sequencing batch reactor (SBR) was operated under different pH conditions to better understand the influence of pH to granulation in enhanced biological phosphorus removal systems. Granules from the SBR were also investigated using scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX). Considerable decreases in the amount of phosphorus released per substrate provided under anaerobic conditions and the content of biomass polyphosphate under aerobic conditions were observed when pH was changed from 7.5 to 7.0, followed by 6.5. Aerobic granulation was also observed at pH 7.0. A number of bacteria with the typical morphological traits of tetrad-forming organisms (TFOs) were observed at pH 7.0, including large members of cluster. Filamentous bacteria were also there in large numbers. The occurrence and growth of granules were further enhanced at pH 6.5. A SEM analysis showed that the aerobic granules had a compact microbial structure with shaperical shape and morphologically consisted of aggregates of small coccoid bacteria and filamentous bacteria encapsulated by extracellular polymeric substance. The main material ions identified by EDX moreover revealed that the structural materials for polyphosphate in the granules include phosphorus, potassium and calcium. Therefore, these results strongly suggested that PAOs are a dominant population in the microbial community of the aerobic granules.

• Journal of Technologic Dentistry
• /
• v.26 no.1
• /
• pp.89-96
• /
• 2004

Hydroxyapatite powder were synthesized by precipitation method, varying pH, and reaction temperature. The powders were heated at 1,200$^{\circ}{\cdots}$ and 1,300$^{\circ}{\cdots}$ for fabrication of dental prosthesis. The results are as follows: Synthesized powder showed the smallest particle in size, under the conditions of pH 11 and reaction temperature 37$^{\circ}{\cdots}$. The hydroxyapatite was partially converted to $\alpha,\;\beta$-TCP at 1,200$^{\circ}{\cdots}$ and 1,300$^{\circ}{\cdots}$. Mechanical strength of sample was affected by such powder preparation conditions as pH and reaction temperature and sintering temperature. The mechanical strength of sample prepared under the same conditions was increased with increasing pH, reaction temperature and sintering temperature.

• Applied Biological Chemistry
• /
• v.38 no.3
• /
• pp.248-253
• /
• 1995

Optimum conditions for the enzymatic hydrolysis of isolated sesame meal protein were investigated. Optimum conditions by papain were $60^{\circ}C$, pH 6.0, 3% enzyme concentration to substrate and 1.5% substrate concentration, respectively. The optimum operating conditions using pepsin were $55^{\circ}C$, pH 9.0, 3% enzyme concentration to substrate and 1% substrate concentration. The optimum operating conditions using trypsin were $60^{\circ}C$, pH 9.0, 1% enzyme concentration to substrate and 1% substrate concentration.

• Asian-Australasian Journal of Animal Sciences
• /
• v.20 no.1
• /
• pp.112-118
• /
• 2007

The present study was conducted to investigate the attributes of ram sexual behaviour under different social conditions. Six intact rams and eight overiectomized ewes were used in this experiment. Ewes were artificially brought into oestrus. All mating traits were recorded every 10 sec during a 1 h mating session under five social conditions viz., ram exposed to single oestrus ewe, ram exposed to single oestrus ewe and audience ram, ram exposed to multiple oestrus ewes, ram exposed to single oestrus ewe with competitor ram and ram exposed to multiple oestrus ewes with competitor ram. Mean intensity of the mating activities during the 1 h mating session under five social conditions was compared. Either vocalization or leg kicking was found to be the predominant teasing activity under all five conditions. Sniffing differed significantly (p<0.05) between different social conditions. Vocalization, leg kicking, and leg kicking with vocalization did not differ significantly (p<0.05) between different social conditions. Mounts/h in the multiple oestrus ewe condition was higher and differed significantly (p<0.05) from other social conditions. Ejaculations/h for the experimental ram was higher when exposed to multiple oestrus ewes in comparison to other social conditions. Mounts/ejaculation was low in the audience ram condition in comparison to the other four social conditions.

• Journal of Environmental Health Sciences
• /
• v.30 no.2
• /
• pp.104-107
• /
• 2004

This study was conducted to evaluate the effects of pH, using gametes, embryos and early development system of three sea urchins species, Hemicentrotus pulcherrimus, Anthocidaris crassispina and Scaphechinus brevis. As the result of performing effects of pH on early embryo development, the conditions of appropriate pH on formation of normal pluteus were pH 7.0-8.0 for H. pulcherrimus, A. crassispina and S. brevis. Otherwise, the conditions of pH 5.0, pH 6.0, pH 9.0 and pH 10.0 damaged the development of early embryos of each testing animal moderately or strongly.