共查询到20条相似文献,搜索用时 11 毫秒
1.
Three α-amylase enzymes were used to hydrolyze wheat starch granules suspended in water below the gelatinization temperature. The rates of hydrolysis were determined at various temperatures, pH, enzyme and starch concentrations. Barley amylase was found to be the “best” enzyme when used at pH 4.5, 45°C and starch and enzyme concentrations of 30 and 8 mg/mL respectively. It was found that under these conditions, 98% of the starch granules were hydrolyzed in 3 hours, the same amount of time used in the industrial cooking process of soluble starch. Starch particles were observed to be attacked at specific points on the surface and then hydrolyzed from the inside-out. Some granules were hydrolyzed at a very fast rate with a first order rate constant estimated to be 40 h?1; but most granules were hydrolyzed slowly according to the Michaelis-Menten model and the best fit parameters were found to depend on enzyme type, pH and temperature. 相似文献
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Masatoshi Matsumura June Hirata 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》1989,46(4):313-326
A kinetic model for simultaneous saccharification and fermentation (SSF) of raw starch is proposed. The model includes the effect of ethanol on an active site for saccharification and the decay of a raw starch affinity site. The kinetic parameters were determined by using the experimental results of a batch saccharification and a long-term repeated-batch SSF of raw sweet potato starch. From analysis of the experimental results it is concluded that two subsites took part in ethanol inhibition, and that the inactivation of the raw starch affinity site was induced by adsorption of glucoamylase onto raw starch. The proposed kinetic model successfully predicted the progress of continuous SSF in a membrane reactor. 相似文献
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The activity of β‐galactosidase immobilized into a poly(2‐hydroxyethyl methacrylate) (pHEMA) membrane increased from 1.5 to 10.8 U/g pHEMA upon increase in enzyme loading. The Km values for the free and the entrapped enzyme were found to be 0.26 and 0.81 mM, respectively. The optimum reaction temperatures for the free and the entrapped β‐galactosidase were both found to be 50°C. Similarly, the optimum reaction pH was 7.5 for both the free and the entrapped enzyme. The immobilized β‐galactosidase was characterized in a continuous system during lactose hydrolysis and the operational inactivation rate constant (kiop) of the entrapped enzyme was found to be 3.1 × 10−5 min−1. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 72: 1367–1373, 1999 相似文献
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The continuous enzymatic production of galactosyl-oligosaccharides (GOS) from lactose as a substrate using a new type of ceramic membrane reactor system was investigated. GOS are non-digestible oligosaccharides and have recently attracted interest as prebiotics. However, the composition of oligosaccharides fraction and the variability in β-glycosidic linkages depend on the enzyme source. In the study presented below, native, physically immobilized, β-galactosidase from Kluyveromyceslactis (EC 3.2.1.23) was used as enzyme to catalyse transgalactosylation reaction to produce GOS, competed against the hydrolysis of lactose into its two component monosaccharides, glucose and galactose. To optimize GOS yielded, process conditions were varied: the average residence time of the enzyme was varied in the range of 13 to 24 min, the trans-membrane pressure (TMP) was in the range of 1 to 2 bar and the initial concentration of substrate was varied from 10 to 30% (w/w). Regarding the conditions investigated here, the maximum oligosaccharide concentration exceeded 38% (w/w) when the average residence time was 24 min, the TMP was 2 bar and an initial lactose concentration of 30% (w/w) was adjusted. 相似文献
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利用乳液酶膜反应器拆分萘普生甲酯实验研究 总被引:1,自引:0,他引:1
利用乳液酶膜反应器进行外消旋萘普生甲酯的水解反应,以制备光学纯对映体(S)-萘普生,反应同时从膜透过侧收集产物,实现反应分离一体化。实验研究了固定酶前后膜传质阻力和反应过程的水相跨膜通量,考察了透过侧的产物浓度、反应器的转化率、产量和对映体选择性。结果表明:固定化酶引起的传质阻力远大于膜本身的阻力;透过侧的产物浓度与水相渗透通量密切相关,通量较低时,产物浓度较高;固定化酶的初始反应速率为3.660μmol/(h.g),为自由酶的20倍以上,固定化酶的对映体过剩值为99%—100%,远高于自由酶的选择性,表明该反应体系为脂肪酶催化拆分反应提供了良好环境。 相似文献
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Wouter Pronk Machteld van der Burgt Gerard Boswinkel Klaas van ’t Riet 《Journal of the American Oil Chemists' Society》1991,68(11):852-856
A hybrid reactor, consisting of a stirred vessel, a hydrophilic membrane loop and a hydrophobic membrane loop, is presented
for the continuous enzymatic hydrolysis of soybean oil in an emulsion. The permeates of the hydrophilic and the hydrophobic
membrane consist of a single water phase and a single lipid phase, respectively. No lipase activity could be detected in the
permeates of both membranes, which implies that all enzyme is retained in the system. An important advantage of this system
is that it combines the high surface area in an emulsion with the containment of lipase in a membrane reactor. It is further
shown that the stability of the system can be improved considerably by the addition of CaCl2 to the water phase. Under comparable conditions the enzyme stability in the hybrid reactor is lower than the stability in
a stirred vessel. The composition of the emulsion appears to influence the flux of the membranes. The flux of the hydrophobic
membrane increases with an increasing oil fraction of the emulsion while the flux of the hydrophilic membrane has an optimum
for two different oil fractions—0 and 0.55 (v/v). 相似文献
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Lúcia Brandão 《Chemical engineering science》2007,62(23):6768-6776
Propyne hydrogenation was studied in a continuous polymeric catalytic membrane reactor (pCMR), both experimentally and theoretically. It was used a poly(dimethylsiloxane) (PDMS) composite membrane with an average thickness of , loaded with 5 wt% of 9 nm diameter Pd clusters. The reaction was conducted at 308 K and several feed compositions at a fixed flow rate were tested.The mathematical model proposed includes the mass balances to the retentate and permeate chambers and the mass balance and transport kinetics through the catalytic membrane. The pCMR model also considers a reaction rate equation composed of two terms: the propyne to propylene and the propylene to propane hydrogenations. The selectivity between these two reactions is described by the bicomponent adsorption of propyne and propylene obtained by the IAST model (thermodynamic selectivity). The proposed model represents quite well the experimental data regarding the flow rates and mixture compositions of the permeate and retentate streams. 相似文献
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Ion Agirre M. Belén Güemez Anatolie Motelica Henk M. van Veen Jaap F. Vente Pedro L. Arias 《American Institute of Chemical Engineers》2012,58(6):1862-1868
Acetals are considered as an important bio‐based diesel additives. Generally, the catalytic production of these compounds from an alcohol and an aldehyde suffers from a low conversion because of thermodynamic limitations. These limitations can be overcome through the in situ removal of the by‐product water using, for example, a water selective membrane. A critical evaluation on the membrane performance, catalyst activity, optimal configuration, and feed composition leads to the conclusion that a combined reaction and separation is unlikely to be advantageous. The water permeance of the selected membrane was assessed to be too low in relation with the catalyst activity. © 2011 American Institute of Chemical Engineers AIChE J, 58: 1862–1868, 2012 相似文献
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Michal Pribyl Rzena Chmelíkov Pavel Hasal Milos Marek 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2002,77(1):51-62
Analysis of penicillin G hydrolysis in a membrane reactor with membrane‐entrapped penicillin G acylase is performed using a mathematical model of the reactor system. An electric field imposed to the reactor is considered to enhance transport rates of reaction components and reaction rate. Diffusion, electrophoretic migration and electro‐osmotic flux across the membrane are considered. The analysis focuses on possible effects of the principal operational parameters (electric field intensity, inlet substrate concentration, membrane thickness) on reactor performance. Multiplicities of steady states are frequently encountered. The membrane reactor performance can be easily targeted towards the required reaction regime by applying a constant or periodically varying electric field to the system. The periodic alternation of the polarity of the electric field substantially increases the effectiveness factor of penicillin hydrolysis compared with the steady state operation. Proper adjustments of electric field intensity may also compensate for the decay in enzyme activity. © 2001 Society of Chemical Industry 相似文献
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Frdric Sannier Jean-Marie Piot Pascal Dhulster Didier Guillochon 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》1994,61(1):43-47
Factors involved in the activity decay of an ultrafiltration reactor during the hydrolysis of hemoglobin by pepsin were studied. Biochemical and hydrodynamic parameters were assessed. The product of hydrolysis showed no inhibitory effect. Autolysis and mechanical damage of pepsin were limited by the presence of hemoglobin. Activity decay was mainly a result of the leakage of pepsin through the membrane. Electrostatic charges carried by either hemoglobin or pepsin were involved in the permeation process. 相似文献
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以苄亚甲基二氯为原料,盐酸为催化剂,在微通道反应器中连续合成了苯甲醛。考察了苄亚甲基二氯水解反应的温度、盐酸催化剂起始浓度、反应物料摩尔比以及停留时间对反应的影响。实验确定了较优的工艺参数组合:在起始浓度为20%(质量分数)的盐酸催化下,水解反应温度为140 ℃,盐酸与苄亚甲基二氯物料摩尔比为15∶1,停留时间为370 s时,苄亚甲基二氯的转化率达到69.2%,GC选择性超过99.9%。与传统生产工艺相比,实现了连续化操作,缩短了反应时间;采用盐酸作催化剂,避免了传统金属催化剂残留对产品的影响。 相似文献
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M. Yakup Arica 《应用聚合物科学杂志》2000,77(9):2000-2008
Poly(2‐hydroxyethylmethacrylate) (pHEMA) membranes were prepared by UV‐initiated photopolymerization of HEMA in the presence of an initiator (α‐α′‐azobisisobutyronitrile, AIBN). The epoxy group, i.e., epichlorohydrin, was incorporated covalently, and the urease was immobilized onto pHEMA membranes by covalent bonding through the epoxy group. The retained activity of the immobilized enzyme was found to be 27%. The Km values were 18 and 34 mM for the free and the immobilized enzymes, respectively, and the Vmax values were found to be 59.7 and 16.2 U mg−1 for the free and the immobilized enzyme. The optimum pHs was 7.2 for both forms, and the optimum temperature for the free and the immobilized enzymes were determined to be 45 and 50°C, respectively. The immobilized urease was characterized in a continuous system and during urea degradation the operational stability rate constant for the immobilized enzyme was found to be 5.83 × 10−5 min−1. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 2000–2008, 2000 相似文献
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M. A. P. Morgado J. M. S. Cabral D. M. F. Prazeres 《Journal of the American Oil Chemists' Society》1996,73(3):337-346
Lysophospholipids and free fatty acids produced by lecithin hydrolysis are important natural compounds with high potential
for application in the food, chemical, and pharmaceutical industries. In this work, the enzymatic hydrolysis of lecithin (essentially
phosphatidylcholine) catalyzed by porcine pancreatic phospholipase A2 (phosphatide 2-acyl-hydrolase, EC 3.1.1.4), encapsulated in mixed reversed micelles of lecithin andbis(2-ethylhexyl) sodium sulfosuccinate (AOT) in isooctane, was carried out in a continuous reversed-micellar membrane bioreactor.
A tubular ceramic membrane with a 10,000 molecular weight (MW) cutoff was installed in an ultrafiltration module to retain
the phospholipase A2 (MW 14,000) and to continuously separate the products from the reaction media. Water and co-factor (Ca++)-containing reversed micelles of lecithin/AOT in isooctane were supplemented to the reactor to compensate for the permeation
of reversed micelles and to continuously supply the substrate. The influence of relevant parameters, such as substrate, AOT
and enzyme concentrations, water content and fluid hydrodynamics, on the performance of the ultrafiltration membrane bioreactor
was investigated. Fluid axial velocity and substrate concentration were the major factors that affected the transport processes
through the membrane. Permeate flow rate increased significantly with fluid axial velocity and decreased with substrate concentration;
on the other hand, water and enzyme concentrations were identified as critical parameters for the final conversion of lecithin.
The relationship between productivity and normalized residence time was analyzed for each set of experimental parameters tested.
Operational stability of the bioreactor was tested in a long-term operation to confirm the high stability of this catalytic
system. 相似文献
17.
Saccharification of modified starch to maltose in a continuous rotating annular chromatograph (CRAC)
M. R. Sarmidi P. E. Barker 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》1993,57(3):229-235
Simultaneous biochemical reaction and separation has been successfully carried out in a continuous rotating annular chromatograph (CRAC) by saccharifying liquefied starch to maltose using the enzyme maltogenase. Maltogenase is a thermostable, exo-acting alpha-amylase. A simple optimisation procedure involving both volume overload and concentration overload was used. For soluble potato starch, maltose conversions of up to 79% were achieved at feed flow rates of up to 400 cm3 h?1 and 15–5% w/v concentrations. The resolution between maltose and dextrin was 0.92. 相似文献
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Satish C Mohapatra James T Hsu 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2000,75(7):519-525
α‐Chymotrypsin from bovine pancrease (EC 3.4.21.1) was entrapped in Ca‐alginate gel particles to carry out hydrolysis of N‐acetyl‐L ‐phenylalanine methyl ester (APME) in batch as well as continuous fixed bed reactor. The enzyme was covalently modified with homo‐bifunctional polyethylene glycol derivatives in order to reduce its leakage from the beads; 85% modification of the ∈‐NH2 groups of lysine residues caused reduction in the enzyme activity by 50%. However, this modification was helpful in a long run because it reduced both enzyme leakage and deactivation. Effective diffusivities and the distribution coefficients of the substrate and the product were determined experimentally, and later used in simulation of a batch experiment employing the beads. A continuous fixed bed reactor with the gel beads was operated to study the deactivation of the enzyme. During a 15‐day period, the enzyme showed about 15% loss in the conversion which occurred only during the first 5 days. After that the enzyme did not deactivate further which demonstrates that this method can be applied for continuous reactions. © 2000 Society of Chemical Industry 相似文献
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Sevinc Korkmaz Yavuz Salt Ayca Hasanoglu Semra Ozkan Inci Salt Salih Dincer 《Applied Catalysis A: General》2009,366(1):102-107
In this study, isobutyl acetate, a valuable solvent in cosmetics, aroma and paint industries, is produced by pervaporation–esterification equilibrium reaction in a batch pervaporation membrane reactor (PVMR) using homogeneous (sulphuric acid) and heterogeneous (Dowex 50W-X8) catalysts. The effects of catalyst loading, catalyst type, reaction time, membrane thickness, temperature and initial molar ratio of reactants were investigated. A cross-linked polydimethylsiloxane (PDMS) membrane selective to esters was prepared and used in PVMR. Batch reactions were carried out also in a simple batch reactor (SBR) without pervaporation under the same conditions to compare the conversions for the reactions with and without pervaporation. In conclusion, PVMR experiments showed that the PDMS membrane can be used to remove the isobutyl acetate formed selectively with acceptable conversions and pervaporation fluxes. 相似文献
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Enzyme hydrolysis of babassu oil in a membrane bioreactor 总被引:1,自引:0,他引:1
F bio Mer on Geraldo Lippel Sant Anna Jr. Ronaldo Nobrega 《Journal of the American Oil Chemists' Society》2000,77(10):1043-1048
This work deals with the enzymatic hydrolysis of babassu oil by immobilized lipase in a membrane bioreactor using unmixed
aqueous and lipid streams. The experimental work was carried out in a flat plate membrane module with two different membranes:
hydrophobic (nylon) and hydrophilic [mixed cellulose esters (MCE)], with different nominal pore sizes ranging from 0.10 to
0.65 μm. Candida cylindracea lipase was adsorbed on the membrane surface area, and the reactor was operated in batch mode. The initial enzymatic rate
increased from 80 to 150 μmol H+/min when the organic phase velocity increased from 1.0×10−3 to 3.0×10−3 m/s, indicating that mass transfer in that phase was the process-limiting step. Calcium ions had a marked effect on immobilized
lipase activity, increasing around twofold the lipolytic activity. Long-term experimental runs showed that the immobilized
lipase remained stable for at least 8 d. The values for immobilized protein and maximal productivities observed for 0.45 μm
membranes were: 1.01 g/m2 and 193 μmol H+/m2·s for MCE membrane and 0.78 g/m2 and 220 μmol H+/m2·s for nylon membrane. The productivities obtained are among the highest values reported in the technical literature. 相似文献