• Microbiology and Biotechnology Letters
• /
• v.20 no.1
• /
• pp.40-45
• /
• 1992

Acidic nucleotidase from Asfiergilius nlger has been partially purified by Sepharose CL-6B gel filtration and DEAE-Sephacel ion exchange chromatography. The optimum pH and temperature for the enzyme reaction with 5'-AMP or 3'-AMP as a substrate were 4.5 and 55%, respectively. However, the optimum temperature became 70% when p-nitrophenyl phosphate was used as a substrate. The enzyme was stable at acidic pH. The enzyme activity was not affected by addition of various nucleotides, nucleosides and inorganic phosphates. Ferric, aluminium, vanadate and molybdate ions inhibited the enzyme activity dramatically. In kinetic studies, $K_m$), values for 3'-AMP, 5'-AMP and p-nitrophenyl phosphate were 1.39 mM, 1.5 mM and 5.77 mM, respectively. The substrate efficiency ($V_{max}/K_m$) shows 3'-AMP is the prefered substrate for the enzyme among tested substrates.

• Journal of Microbiology and Biotechnology
• /
• v.24 no.6
• /
• 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.

• Journal of the Korean Society of Food Science and Nutrition
• /
• v.32 no.3
• /
• pp.400-405
• /
• 2003

The surimi processing from jack mackerel and white croaker muscle using acidic and alkaline solubilization was evaluated. The optimum pH for solubilizing protein in acidic and alkaline range was around 2.5 and 10.5, respectively. The optimum pH value for recovery of protein was around 5. The protein solubility was decreased with increase of salt. The homogenized speed and time for maximum solubility were below 9,500 rpm and 30s, respectively The optimum ratio of water to minced muscle was 6 by evaluating breaking force, deformation and whiteness of cooked gel. The protein yield of alkaline processing is higher than that of conventional processing. In addition, the waste water of conventional processing had high solid, nitrogen content and chemical oxygen demand compare to those of acidic and alkaline processing.

• Applied Chemistry for Engineering
• /
• v.26 no.4
• /
• pp.511-514
• /
• 2015

A pretreatment process of cellulose decomposition to a monosaccharide plays an important role in the cellulosic ethanol production using the lignocellulosic biomass. In this study, a cellulosic ethanol was produced by using acidic hydrolysis and enzymatic saccharification process from the lignocellulosic biomass such as rice straw, sawdust, copying paper and newspaper. Three different pretreatment processes were compared; the acidic hydrolysis ($100^{\circ}C$, 1 h) using 10~30 wt% of sulfuric acid, the enzymatic saccharification (30 min) using celluclast ($55^{\circ}C$, pH = 5.0), AMG ($60^{\circ}C$, pH = 4.5), and spirizyme ($60^{\circ}C$, pH = 4.2) and also the hybrid process (enzymatic saccharification after acidic hydrolysis). The yield of cellulosic ethanol conversion with those pretreatment processes were obtained as the following order : hybrid process > acidic hydrolysis > enzymatic saccharification. The optimum fermentation time was proven to be two days in this work. The yield of cellulosic ethanol conversion using celluclast after the acidic hydrolysis with 20 wt% sulfuric acid were obtained as the following order : sawdust > rice straw > copying paper > newspaper when conducting enzymatic saccharification.

• Journal of environmental and Sanitary engineering
• /
• v.18 no.1
• /
• pp.41-50
• /
• 2003

Traditionally the supernatant after chemical treatment of metal acid wastewater is discharged in environment. The supernatant can be used as a coagulant as it contains effective metals. The aim of this study is to investigate the feasibility of treatment of dyeing wastewater using the supernatant after treatment by magnesium hydroxide and dolomite($Ca{\cdot}Mg(CO_3)_2$), of acidic metal wastewater. In dyeing wastewater treatment with the supernatant, optimum pH and dosage were determined. COD, turbidity and color were analyzed to evaluate the performance of treatment. In the case of magnesium hydroxide, the optimum dosage was 10%(v/v) for supernatant A and 3%(v/v) for supernatant B. Color, turbidity and COD removal was 99~100%, 85~97% and 43~53%, respectively. In the case of dolomite, the optimum dosage was 10%(v/v) for supernatant A and 3% for supernatant B. Color, turbidity and COD removal was 96~99%, 62~9l% and 52~53%, respectively.

• Journal of Animal Science and Technology
• /
• v.59 no.9
• /
• pp.20.1-20.9
• /
• 2017

Background: Ribonuclease (RNase) is one of the few toxic proteins that are present constantly in snake venoms of all types. However, to date this RNase is still poorly studied in comparison not only with other toxic proteins of snake venom, but also with the enzymes of RNase group. The objective of this paper was to investigate some properties of RNase from venom of Vietnam cobra Naja atra. Methods: Kinetic methods and gel filtration chromatography were used to investigate RNase from venom of Vietnam cobra. Results: RNase from venom of Vietnam cobra Naja atra has some characteristic properties. This RNase is a thermostable enzyme and has high conformational stability. This is the only acidic enzyme of the RNase A superfamily exhibiting a high catalytic activity in the pH range of 1-4, with $pH_{opt}=2.58{\pm}0.35$. Its activity is considerably reduced with increasing ionic strength of reaction mixture. Venom proteins are separated by gel filtration into four peaks with ribonucleolytic activity, which is abnormally distributed among the isoforms: only a small part of the RNase activity is present in fractions of proteins with molecular weights of 12-15 kDa and more than 30 kDa, but most of the enzyme activity is detected in fractions of polypeptides, having molecular weights of less than 9 kDa, that is unexpected. Conclusions: RNase from the venom of Vietnam cobra is a unique member of RNase A superfamily according to its acidic optimum pH ($pH_{opt}=2.58{\pm}0.35$) and extremely low molecular weights of its major isoforms (approximately 8.95 kDa for RNase III and 5.93 kDa for RNase IV).

• Journal of Korean Society of Water and Wastewater
• /
• v.20 no.1
• /
• pp.71-78
• /
• 2006

The removal of protozoa in the coagulation process was evaluated under the different pH and turbidity using the jar test after the addition of polyaluminium chloride (PAC) as a coagulant. Two well-known protozoa of Cryptosporidium parvum and Giardia lamblia were tested at the same time with turbidity, the critical water quality parameter of the water treatment process. Both protozoa were removed about 1log (and up to 2log) at the optimum injection of PAC. The source water turbidity and pH affected the removal of protozoa and turbidity. At neutral and alkaline pH, 1.3-1.7log removal of protozoa for low turbid water with 5NTU, and 1.6-2.3log removal for high turbid water with 30NTU were achieved. However, at acidic pH, maximum 0.8-1.0log and 1.1-1.2log were removed for low and high turbid water, respectively, at the optimum PAC injection of 15mg/L. The relation of protozoa and turbidity removals were expressed as the 1st order equation (significantly positive relation) in the most of the tested conditions. In addition, the relation of protozoan removals with residual turbidity were also expressed the 1st order equation (significantly negative relation), although the significance of the equations were reduced at acidic pH. Therefore, residual turbidity could be a good index of efficient protozoan removal in the coagulation process, probably except at the low pH condition.

• Bulletin of the Korean Chemical Society
• /
• v.15 no.10
• /
• pp.832-835
• /
• 1994

The ${alpha}$-amylase gene of Bacillus licheniformis has been cloned and two mutant ${alpha}$-amylase genes of which histidine 235 was changed to glutamine (H235Q) and aspartic acid 328 to glutamic acid (D328E) have been produced by site-directed mutagenesis. The kinetic parameters, optimum pH and thermostability of wild type(WT) and these two mutant amylases expressed in E. coli MC1061 have been compared after purification. The $K_m$ values of WT, H235Q and D328E ${alpha}$-amylases were 0.22%, 0.73%, and 0.80% respectively, when using starch as the substrate. The $V_max$ values of wild type ${alpha}$ -amylase and mutant ${alpha}$-amylases were 0.6-0.7%/minute, and did not show any significant differences among them. The optimum pH of D328E ${alpha}$-amylase was shifted to more acidic pH. Also, the thermostability of H235Q ${alpha}$-amylase was increased compared to the wild type ${alpha}$-amylase.

• Korean Journal of Microbiology
• /
• v.14 no.1
• /
• pp.17-24
• /
• 1976

Celluloytic microorgnasims were isolated form the various sources and four of them were identified as Trichoderma roningi, Aspergillus niger, Penicillium chrysogenum, and Streptomyces sp. The induction of extracellular5 cellulase of these species in the liquid culture media containing carboxymethylcellulose (CMC) or Avicel as inducer showed that CMC was a better effective inducer for the production of CMCase(Cx cellulase component) as well as Avicelase(C$_{1}$ cellulase component) than Avicel. It is believed that certain hydrolysis products of cellulose(CMC) could serve as an inducer for an enzyme synthesis. In T. roningi, Asp. niger, and Strptomyces sp., the optimum temperature of CNCase on CMC-culture medium was 50.deg. but temperature around 40.deg.C was found to be optimum for the activities of CMCase prepared from P.ehrysogenum. The optimum temperature for Avicelase activitiles on Avicel-culture media of T. roningi and P. chrysogenum was $40{\circ}C$ whereas temperature $50{\circ}C$ was found to be optimum for Avicelase from A.niger and Streptomyces sp. The optimal activities of these CNCase and Avicelase prepared from. T. ronigi, Pen.chrysogenum and Streptomyces sp. were found similarly to be at pH's around 5.4 and 6.0 while pH 4.8 was optimum for the activities of CMCase and Avicelase from A.niger, indicating that A.niger in acidic media would yield an enzyme of high activity.

• Natural Product Sciences
• /
• v.10 no.6
• /
• pp.302-305
• /
• 2004

The lipase and phospholipase activities of meals of resting seeds of C. roxburghianum were studied at different temperatures, solvents and pH. Both the enzymes showed the maximum activities at $40^{\circ}C$ and in n-heptane used as solvent. However, lipase showed maximum activities at two different pH, one at pH 5 (acidic) and other at pH 8 (alkaline) whereas phospholipase showed only one pH optimum at pH 8. During the course of germination, the lipase showed an increase whereas reverse was the case with phospholipase.