Search Results - (Author, Cooperation:D. Ryu)

2016-04-30

American Association for the Advancement of Science (AAAS)

0036-8075

1095-9203

Biology

Chemistry and Pharmacology

Computer Science

Medicine

Natural Sciences in General

Physics

2013-05-24

Nature Publishing Group (NPG)

0028-0836

1476-4687

Biology

Chemistry and Pharmacology

Medicine

Natural Sciences in General

Physics

Aging/genetics/metabolism ; Animals ; Anti-Bacterial Agents/pharmacology ; Caenorhabditis elegans/drug effects/genetics/*physiology ; Caenorhabditis elegans Proteins/genetics/metabolism ; Doxycycline/pharmacology ; Evolution, Molecular ; Female ; Longevity/drug effects/genetics/*physiology ; Male ; Mice ; Mice, Inbred Strains ; Mitochondria/drug effects/genetics/*metabolism ; Mitochondrial Proteins/genetics/*metabolism ; Quantitative Trait Loci ; RNA Interference ; Reproducibility of Results ; Ribosomal Proteins/genetics/*metabolism ; Sirolimus/pharmacology ; Unfolded Protein Response/genetics/physiology

2018-11-02

The Society of Nuclear Medicine (SNM)

0022-3123

Medicine

1089-7550

AIP Digital Archive

Physics

A series of GaN:Mg structures were grown in molecular beam epitaxy, using either one or two rf nitrogen sources, and in metalorganic chemical vapor deposition systems with varying Mg flux. Acceptor energies were measured using the Hall effect and admittance spectroscopy techniques. The acceptor energies were found to be different for the two methods, i.e., 135–155 meV for the Hall effect measurement and 80–115 meV for the admittance spectroscopy measurement. The apparently small acceptor energies from the admittance spectroscopy measurement were explained, through a simulation process, by the combined effects of (1) high Mg acceptor concentration with no other free carrier sources, and (2) the Mg emission kinetics assisted by the Frenkel–Poole field effect in the GaN:Mg structures. © 2000 American Institute of Physics.

Electronic Resource

1750-3841

Blackwell Publishing Journal Backfiles 1879-2005

Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition

Process Engineering, Biotechnology, Nutrition Technology

The effects of autoclaving, baking, extrusion, frying, and roasting on the stability of moniliformin (MON) in spiked (5 μg/g of MON) corn-based food products were investigated. Roasting corn meal at 218 °C for 15 min had the most significant effect (p ≤ 0.05) on the reduction of MON (44.6%). Autoclaving creamed corn at 121 °C for 65 min resulted in only 10% reduction of MON. Reductions of MON ranging from 5.4 to 28.9% were observed when corn chips were prepared from spiked masa. MON was reduced by 42.2% when corn muffins were baked and by 26.7% when corn grits were extruded. Overall, MON showed heat stability similar to or greater than other Fusarium mycotoxins such as deoxynivalenol and fumonisin B1

Electronic Resource

1476-4687

Nature Archives 1869 - 2009

Biology

Chemistry and Pharmacology

Medicine

Natural Sciences in General

Physics

[Auszug] THE measurement of growth rates of micro-organisms by determining the rate of change of the concentration of a cellular component such as protein, DNA, or RNA is well established1, as is the use of dry weight or optical density measurements on the growing culture to approximate the dry weight2. ...

Electronic Resource

1432-0614

Springer Online Journal Archives 1860-2000

Biology

Process Engineering, Biotechnology, Nutrition Technology

Abstract A two-stage, cyclic fed-batch bioprocess was designed, and its performance evaluated to improve rice α-amylase productivity by the yeast Yarrowia lipolytica SMY2 (MatA, ade1, ura3, xpr2), ATCC 201847, containing a replicative plasmid coding for a rice α-amlyase. Transcription of the recombinant gene is controlled by the XPR2 promoter. The first stage (or growth stage) was operated in the fed-batch mode, and the growth medium, designed to maintain a constant high cell density (i.e., 60 g/l), was fed according to a predetermined and preprogrammed optimal feed rate which, in turn, maintained the specific cell growth rate at an optimal value (i.e., 0.1 h−1). Typically, when the volume in the first stage reached a preset value, a portion of culture broth (i.e., 55%) was transferred to the second stage (or production stage). The remaining cells in the growth stage were then fed with fresh growth medium according to the bioprocess control strategy developed, while induction of α-amylase expression and its production was taking place in the second stage. The second stage was also operated in the fed-batch mode, and the production medium designed to maintain a constant high cell density and high productivity of heterologous protein was fed at a predetermined and preprogrammed rate, which maintained the specific cell growth rate at an optimal level. The volumetric α-amylase productivity achieved (1835 units l−1 h−1) from the two-stage, cyclic fed-batch culture process was twofold higher than that of the fed-batch culture process. The genetic stability of the recombinant strain and the design of optimal media for growth and production stages are also critically important to a successful implementation of the two-stage, cyclic fed-batch process for production of heterologous protein.

Electronic Resource

1432-0614

Springer Online Journal Archives 1860-2000

Biology

Process Engineering, Biotechnology, Nutrition Technology

Summary In ethanol production with immobilized yeast a major problem is the provision of nutrients to these highly concentrated cells. O2 being one of the nutrients of utmost importance to yeast cells, was fed into a column packed with beads with a cell loading of more than 40 g/l. Since addition of large volume of air or O2 to a cylindrical column reactor would aggravate the problems of pressure build up and channelling caused by the evolving CO2 gas, a tapered-column reactor and pulsed flow of oxygen gas was used. The supplement of O2 gas to the tapered column increased the productivity from 21.1 g ethanol x (l gel x h)-1 to 26.7 g x (l gel x h)-1, when the ethanol concentration at the outlet was about 80 g/l. The yield coefficient of ethanol was also increased from 0.41 g ethanol/g glucose to 0.43 after O2 supplement was started. The effects of frequency and duration of O2 supplement were also determined.

Electronic Resource

0006-3592

Chemistry ; Biochemistry and Biotechnology

Wiley InterScience Backfile Collection 1832-2000

Biology

Process Engineering, Biotechnology, Nutrition Technology

Two-step microbial transformation of 16α-hydroxycortexolone to its 1-dehydro-11α-hydroxy derivative, without isolating an intermediate, was achieved with an overall yield of 72% of product at a steroid substrate concentration of 3 mg/ml. The process included formation of the cycloborate complex of the substrate, hydroxylation of the borate complex with a suspension of Aspergillus ochraceus mycelium in phosphate buffer, and dehydrogenation of the 11α-hydroxylated intermediate with acetone-dried Arthrobacter simplex cells. The desired product was then obtained by breaking the resultant borate complex through acidification.

6 Ill.

Electronic Resource

0006-3592

Chemistry ; Biochemistry and Biotechnology

Wiley InterScience Backfile Collection 1832-2000

Biology

Process Engineering, Biotechnology, Nutrition Technology

Some results of our studios on transformation of steroids by mixed culture fermentation are presented in this paper. Arthrobacter simplex was paired in turn with each of the following: Streptomyces roseochromogenes, Curvularia lunata, Absidia coerulea, and Aspergillus ochraceus. The steroid substrates examined for multiple transformation were 16α-hydroxy-cortexolone, 16α-hydroxy-cortexolone 16,17-acetonide, 9α-fluorohydrocortisone, 9α-fluorohydrocortisone 21-acetate, and 9α-fluorohydrocortisone 21-hemisuccinate. The effects of media, steroid substrate, and microbial interaction in a mixed culture on the induction and repression of steroid transforming enzymes were unique to each case studied. The reaction mechanism of the multiple steroid transformation was also found to vary from one mixed culture system to another. Two different reaction mechanisms were observed, namely, consecutive and parallel. In the former, one of the two enzymatic reactions always preceded the other, while in the latter, two different enzyme reactions occurred simultaneously, thereby giving rise to two different intermediates. Multiple transformation of steroids by a single step mixed culture fermentation has potential economic advantages.

3 Ill.

Electronic Resource

0006-3592

Chemistry ; Biochemistry and Biotechnology

Wiley InterScience Backfile Collection 1832-2000

Biology

Process Engineering, Biotechnology, Nutrition Technology

The purpose of this experimental study was to examine the transient response of a chemostat-type continuous culture of Escherichia coli B to step changes in temperature by following transient limiting substrate concentration and calculating from it the transient growth rate. The transient response to step changes of temperature was tested for four different situations. In the first two cases, temperature was shifted down from 37 to 27°C., and 37 to 32°C. In the last two, it was shifted up from 32 to 37°C., and 27 to 37°C. When the temperature was shifted up, the growth rate increased rather rapidly to its transient maximum value and then decreased slowly until it, settled back into the steady-state value. On the other hand, when the temperature was shifted down, the growth rate decreased relatively rapidly to its transient minimum and then it slowly increased and returned gradually to the steady-state value. The magnitude of the transients was less than would be expected if the transient growth rates followed an Arrhenius function.

7 Ill.

Electronic Resource

0006-3592

Chemistry ; Biochemistry and Biotechnology

Wiley InterScience Backfile Collection 1832-2000

Biology

Process Engineering, Biotechnology, Nutrition Technology

The kinetics of the enzymatic hydrolysis of sucrose by invertase have been examined, with particular emphasis on high substrate concentration. Initial rates of reaction were determined by following the production of glucose directly as a function of time over a wide range of substrate concentrations (0.04M to 2.06M). The resulting data reveal a reaction rate that increases gradually until the sucrose concentration reaches about 0.29M, after which the reaction velocity decreases with increasing sucrose concentration. Previous workers (e.g., Nelson and Schubert1) have reported a peak reaction velocity as determined by indirect polarimetric measurements of glucose, at a sucrose concentration of about 0.17M. These measurements, however, neglect the intermediate oligosaccharides formed by the transferase action of invertase,8-10 and assume equal amounts of glucose and fructose. According to Anderson et al.,10 these oligosaccharides interfere by producing an erroneously low reaction rate. Experimental results of this work confirm Anderson's observations, and show a further reaction rate increase of nearly 20% between sucrose concentrations of 0.177M and 0.285M under the same conditions of temperature, pH, and enzyme-concentration.Effects of substrate diffusion, solution viscisity, water concentration, and substrate inhibition were experimentally studied and the results incorporated into a kinetic model that has proven satisfactory in modeling the experimental results. This model takes into account inhibition by primary substrate, with concentration of the secondary substrate water, as a rate limiting factor at sucrose concentrations greater than 0.285M.The effects of the mixing, in terms of volumetric power input, on the relation rate have been tested. Approximately 40-fold increase in volumetric power input caused on increase in the reaction rate. These experiments have shown that bulk mass transfer is not a rate limiting factor under the experimental conditions.

9 Ill.

Electronic Resource

0006-3592

Chemistry ; Biochemistry and Biotechnology

Wiley InterScience Backfile Collection 1832-2000

Biology

Process Engineering, Biotechnology, Nutrition Technology

2 Ill.

Electronic Resource

0006-3592

Chemistry ; Biochemistry and Biotechnology

Wiley InterScience Backfile Collection 1832-2000

Biology

Process Engineering, Biotechnology, Nutrition Technology

Glucose isomerase in the form of heat-treated whole-cell enzyme prepared from Streptomyces phaeochromogenus follows the reversible single-substrate reaction kinetics in isomerization of glucose to fructose. Based on the Kinetic constants determined and the mathematical model of the reactor system developed, the preformance of a plug-flow-type continuous-enzyme reactor system was studied experimentally and also simulated with the aid of a computer for the ultimate objective of optimization of the glucose isomerase reactor system.The enzyme decay function for both the enzyme storage and during the use in the continuous reactor, was found to follow the first-order decay kinetics. When the enzyme decay function is taken into consideration, the ideal homogeneous enzyme reactor kinetics provided a satisfactory working model without further complicatin of the mathematical model, and the results of computer simulation were found to be in good agreement with the experimental results. Under a given set of constraints the performance of the continuous glucose isomerase reactor system can be predicted by using the computer simulation method described in this paper.The important parameters studied for the optimization of reactor operation were enzyme loading, mean space time of the reactor, substrate feed concentration, enzyme decay constants, and the fractional conversion, in addition to the kinetic constants. All these parameters have significant effect on the productivity.Some unique properties of the glucose isomerization reaction and its effects on the performance of the continuous glucose isomerase reactor system have been studied and discussed. The reaction kinetics of glucose isomerase and the effects of both the enzyme loading and the changes in reaction rate within a continuous reactor on the productivity are all found to be of particular importance to this enzyme reactor system.

15 Ill.

Electronic Resource

0006-3592

Lithospermum erythrorhizon ; nitrate ; PAL and HMGR activity ; shikonin dervative production ; Chemistry ; Biochemistry and Biotechnology

Wiley InterScience Backfile Collection 1832-2000

Biology

Process Engineering, Biotechnology, Nutrition Technology

The activities of the biosynthetic enzmes phenylalanine ammonia lyase (PAL) and 3-hydroxy-3-methylglutaryl-CoA-reductase (HMGR) were measured in cells transferred from growth to production medium in a two-stage batch culture. It was found that both these enzymes showed transient increases, PAL (three- to fourfold) and HMGR (two- to four-fold), at or near the point of exhaustion of nitrogen source (NO3). Production of shikonin derivatives also started at this time. The addition of excess nitrate to the medium shortly before nitrate exhaustion (days 6-8) markedly reduced the final product yield (by 70-80%) while addition of excess nitrate in the later stationary growth phase (days 14-16) had no significant effect. When the production rate of shikonin derivatives was correlated with PAL activity, it was observed that production rate is very low (less than 1 mg/L · day) at low levels of PAL activity (below 0.1 unit/mg protein). Once a threshold level of PAL activity (about 0.15 unit/mg protein) is reached, the biosynthetic rate of shikonin derivatives increases. Such a relationship could not be deduced for HMGR activity. It was concluded that the production of shikonin derivatives may be limited at the phenylalanine deaminating step at low levels of PAL activity.

5 Ill.

Electronic Resource