• Title/Summary/Keyword: hydrolysis

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High Char-Yield in AN-AM Copolymer by Acidic Hydrolysis of Homopolyacrylonitrile

  • Cheng, Run;Zhou, You;Wang, Jing;Cheng, Yumin;Ryu, Seungkon;Jin, Riguang
    • Carbon letters
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    • v.14 no.1
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    • pp.34-39
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    • 2013
  • Acrylonitrile (AN)-acrylamide (AM) copolymers were prepared by nitric acidic hydrolysis of homopolyacrylonitrile. The acrylamino group increased as a function of hydrolysis time, while crystallinity decreased. Differential scanning calorimetry and a thermal gravimetric analysis indicated that the acylamino introduced by acidic hydrolysis effectively enhanced the cyclization reaction at low temperature due to the change of the cyclization reaction mechanism. Char-yield of AN-AM copolymers also gradually increased with increasing hydrolysis time. The maximum char-yield was 49.48% when hydrolized at $23^{\circ}C$ in 65% nitric acid solution for 18 h, which was 30% higher than that of non-acidic hydrolysis of homopolyacrylonitrile. Simulation of the practical process also showed an increase of char yields, where the char yields were 55.43% and 62.60% for homopolyacrylonitrile and copolyacrylonitrile, respectively, with a hydrolysis time of 13 h.

Characterization of Levan Hydrolysis Activity of Levansucrase from Zymomonas mobilis ATCC 10988 and Rahnella aquatilis ATCC 33071

  • Jang, Ki-Hyo;Kang, Soon-Ah;Kim, Chul-Ho;Lee, Jae-Cheol;Kim, Mi-Hyun;Son, Eun-Wha;Rhee, Sang-Ki
    • Food Science and Biotechnology
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    • v.16 no.3
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    • pp.482-484
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    • 2007
  • To investigate production and hydrolysis of levan, the levansucrase enzymes from Zymomonas mobilis ATCC 10988 and Rahnella aquatilis ATCC 33071 were used. The optimum temperature of R. aquatilis levansucrase for levan formation was $37^{\circ}C$, whereas that of Z. mobilis was $4^{\circ}C$, under the experimental conditions. Both levansucrases also catalyzed the reverse levan hydrolysis reaction. Levan hydrolysis reactions from both levansucrases were temperature dependent; high temperature ($20^{\circ}C$) was more favorable than low temperature ($4^{\circ}C$) by 4 times. Fructose was the only product from hydrolysis reaction by both levansucrases, showing that both levansucrases mediated the hydrolysis reaction of exo-enzyme acting. In both enzymes, initial levan hydrolysis activity was almost accounted to 1% of initial levan formation activity. The results allow the estimation of the fructose release rate in enzyme processing conditions.

Autohydrolysis and Enzymatic Saccharification of Lignocellulosic Materials(III) - Recycling and Reutilization of Cellulase Enzyme - (목질 재료의 자기가수분해 및 효소당화에 관한 연구 (Ⅲ) - Cellulase 효소의 회수 및 재사용 -)

  • Cho, Nam-Seok
    • Journal of the Korean Wood Science and Technology
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    • v.17 no.3
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    • pp.45-51
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    • 1989
  • A major problem in the enzymatic hydrolysis of lignocellulosic substrates is the very strong bonding of cellulase to lignin and even cellulose in the hydrolysis residues. This phenomenon inhibits recycle of the cellulase which is a major expense of the enzymatic hydrolysis process. In this paper, autohydrolyzed wood was delignified by two-stage with a 0.3% Na OH extraction and oxygen-alkali bleaching and was subjected to enzymatic hydrolysis with cellulase. Also, an improved almost quantitative recycle process of cellulase enzyme was discussed. In enzyme recovery by affinity method. the first recycling showed relatively high hydrolysis rate of 97.4%. Even at the third recycle. hydrolysis rate was 86.7 percents. In the case of cellulase recovery by ultrafiltration method, first 2 recycling treatments resulted very high hydrolysis rate(97.0-97.7%). Even the third recycling showed about 94.2%. Authoydrolysis of oak wood followed by 2-stage delignification with alkali and oxygen-alkali produced a substrate for enzymatic hydrolysis that allowed almost quantitative recycle of cellulase.

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Characterization of Kinetics of Urea Hydrolysis in A Newly Reclaimed Tidal Soils

  • Kim, Hye-Jin;Park, Mi-Suk;Woo, Hyun-Nyung;Kim, Gi-Rim;Chung, Doug-Young
    • Korean Journal of Soil Science and Fertilizer
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    • v.44 no.1
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    • pp.84-90
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    • 2011
  • It is imperative to study the hydrolysis of urea in high saline-sodic condition of a newly reclaimed tidal land in order to overcome the problems associated with use of urea fertilizer. The methodology adopted in this study tried to get a convenient way of estimating rate for N transformation needed in N fate and transport studies by reviewing pH and salt contents which can affect the microbial activity which is closely related to the rate of urea hydrolysis. The hydrolysis of urea over time follows first-order kinetics and soil urease activity in reclaimed soils will be represented by Michaelis-Menten-type kinetics. However, high pH and less microorganisms may delay the hydrolysis of urea due to decrease in urease activity with increasing pH. Therefore, the rate of urea hydrolysis should adopt $V_{max}$ referring enzyme activity ($E_0$) accounting for urease concentration which is indicative for urea hydrolysis, especially in a high saline and sodic soils.

Presteady State Kinetics of ATP Hydrolysis by Escherichia coli Rho Protein Monitors the Initiation Process

  • Jeong, Yong-Ju;Kim, Dong-Eun
    • Bulletin of the Korean Chemical Society
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    • v.27 no.2
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    • pp.224-230
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    • 2006
  • Escherichia coli transcription termination factor Rho catalyzes the unwinding of RNA/DNA duplex in reactions that are coupled to ATP binding and hydrolysis. We report here the kinetic mechanism of presteady state ATP binding and hydrolysis by the Rho-RNA complex. Presteady state chemical quenched-flow technique under multiple turnover condition was used to probe the kinetics of ATP binding and hydrolysis by the Rho-RNA complex. The quenched-flow presteady state kinetics of ATP hydrolysis studies show that three ATPs are bound to the Rho-RNA complex with a rate of $4.4\;{\times}\;10^5M^{-1}s^{-1}$, which are subsequently hydrolyzed at a rate of $88s^{-1}$ and released during the initiation process. Global fit of the presteady state ATP hydrolysis kinetic data suggests that a rapid-equilibrium binding of ATP to Rho-RNA complex occurs prior to the first turnover and the chemistry step is not reversible. The initial burst of three ATPs hydrolysis was proposed to be involved in the initialization step that accompanies proper complex formation of Rho-RNA. Based on these results a kinetic model for initiation process for Rho-RNA complex was proposed relating the mechanism of ATP binding and hydrolysis by Rho to the structural transitions of Rho-RNA complex to reach the steady state phase, which is implicated during translocation along the RNA.

Characteristics of Acid Hydrolysis Indigo Extracted from Indigo(Polygonum tinctorium L.) Leaves (쪽잎 추출 산가수분해 인디고의 특성)

  • Go, In-Hee;Choi, Tae-Ho
    • Journal of Korea Technical Association of The Pulp and Paper Industry
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    • v.48 no.3
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    • pp.57-65
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    • 2016
  • Indigo (Polygonum tinctorium L.) is a typical blue dye which had been used from ancient times. This study was going to shade the complicated traditional methods extracting indigo dye by the fermentation and producing as adsorbate on calcium hydroxide, which says so called as the 'Indigo lime'. Accordingly we were going to make indigo through the hydrolysis of the hot water extractives of indigo leaves simply. During hot-water extraction, ${\beta}$-glucosidase which required hydrolysis of the linkage between indigo and glucose was not activated. To achieve this goal, indican was acid-hydrolyzed to glucose and indigo. The acetic acid, citric acid, hydrochloric acid, and sulfuric acid were used for the hydrolysis of hot water extractives. The hydrolysis conditions of extractives performed in water bath at $80^{\circ}C$ for 120 minutes and in an autoclave for 120 minutes. In the acid hydrolysis of extracted indican by hot water, the indican yields of acetic acid and hydrochloric acid hydrolysis were higher than sulfuric acid in water bath. Also, the indican yield of hydrochloric acid hydrolysis was better than sulfuric acid in autoclave. The hot water extracted indican was confirmed by HPLC analysis and its structure was confirmed by UV-Vis and FT-IR spectroscopy, compared with isolated indigo and commercial synthesized indigo. This improved extraction and hydrolysis methods can be replace the traditional indigo making method.

Scale- Up of Water-Oil Hydrolysis System

  • Hur, Byung-Ki;Kim, Eun-Ki
    • Journal of Microbiology and Biotechnology
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    • v.9 no.6
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    • pp.773-777
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    • 1999
  • Scale-up experiments for hydrolysis of beef tallow, fat, and palm kernel with lipase derived from Candida cylindracea were carried out in 1-1, 100-1, and 10,000-1 reactors. The optimum agitation speed for the hydrolysis of the 1-1 reactor was investigated and found to be 350rpm, and this was a basis for the scale-up of agitation speed. The hydrolysis system in this work was the oil-water system in which the hydrolysis seems to process a heterogeneous reaction. An emulsion condition was the most important factor for determining the reaction rate of hydrolysis. Therefore, the scale-up of agitation speed was performed by using the power n = 1/3 in an equation of the rules of thumb method. The geometrical similarity for scaling-up turned out to be unsatisfactory in this study. Thus, the working volume per one agitator was used for the scale-up. In the case of scale-up from a 1-1 reactor to a 100-1 reactor, the hydrolysis of palm kernel was very much scaled-up by initiating the rules of thumb method. However, the hydrolysis of fat and beef tallow in a 100-1 reactor was a little higher than that of the 1-1 reactor because of the difference of geometrical similarity. The scale-up of hydrolysis from the 100-1 reactor to the 10,000-1 reactor was improved compared to that of the 1-1 to 100-1 reactor. The present results indicated that the scale-up of hydrolysis in the oil-water system by the rules of thumb method was more satisfactory under the condition of geometrical similarity. Even in the case where geometrical similarity was not satisfactory, the working volume per one agitator could be used for the scale-up of a heterogeneous enzyme reaction.

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Hydrolysis Characteristics of Amylase from Alkaline-Tolerant Bacillus sp. on the Raw Starch (알칼리 내성 Bacillus sp.가 생산하는 Amylase의 생전분 분해 특성)

  • 이신영;조택상
    • KSBB Journal
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    • v.13 no.5
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    • pp.621-625
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    • 1998
  • The raw starch hydrolysis by amylase prepared from alkaline-tolerant Bacillus sp. were investigated. Degree of hydrolysis(%) of 5%(w/v) raw rice, corn and potato starch by this enzyme were about 40, 25 and 20%, respectively. The hydrolysis action on raw starch by change of blue value was similar to the action pattern of exo ${\beta}$-amylase. The hydrolysis products of rice starch were mainly glucose and maltose. Oligosaccarides were also detected. From the above results, this enzyme was considered as exo type ${\alpha}$-amylase. This enzyme activity on the raw starch and the gelatinized starch were 28.40 and 86.60 IU/mg protein, respectively, and the ratio of raw starch-digesting activity to gelatinized starch-digesting activity (raw starch digestivity) was about 32%. The Km values for the raw and the gelatinized starch were 4.22 and 3.0mg/mL, respectively, and the VmaX values were 0.20 and 0.31mg/mL/min, respectively.

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Alkaline Hydrolysis of Alkyl Alkylphosphinate and Alkyl Phenylphosphinates (알킬 알킬포스피네이트와 알킬 페닐포스피네이트들의 염기성 가수분해)

  • Yang, Il-Woo;Chung, Yeong-Jin
    • Journal of the Korean Applied Science and Technology
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    • v.19 no.3
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    • pp.161-166
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    • 2002
  • The alkaline hydrolysis of alkyl alkylphosphinate and alkyl phenylphosphinates have been studied at room temperature. The hydrolysis proceeded as an one-stage reaction($S_{N}$ 2) and involved a nucleophilic attack of the hydroxyl ion on the phosphorus atom. And the length of the alkoxy group in the phosphinate esters affected on hydrolysis. Therefore, the alkaline hydrolysis may be used as a method to decompose the chemical agents.

A Study on the Kinetics and Mechanism of Hydrolysis of N-tert-Butyl-${\alpha}$-Phenylnitrone Derivatives (N-tert-Butyl-${\alpha}$-Phenylnitrone 유도체의 가수분해 반응메카니즘과 반응속도론적 연구)

  • Gwak, Chun-Geun;Lee, Kwang-Il
    • Journal of the Korean Applied Science and Technology
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    • v.15 no.2
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    • pp.1-9
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    • 1998
  • The rate constants of hydrolysis of N-tert-butyl-${\alpha}$-phenylnitrone and its derivatives have been determined by UV spectrophotometry at $25^{\circ}C$ and a rate equation which can be applied over a wide pH range was obtained. On the basis of rate equations derived and judging from the hydrolysis products obtained and general base and substituent effects, plausible mechanism of hydrolysis in various pH range have been proposed. Below pH 4.5, the hydrolysis was initiated by the protonation and followed by the addition of water to ${\alpha}-carbon$. Above pH 10.0, the hydrolysis was proceeded by the addition of hydroxides ion to ${\alpha}-carbon$. In the range of 4.5${\sim}$10.0 the addition of water to nitrone was rate controlling step.