Continuous Isomerization Research Articles

Continuous isomerization of glucose to fructose using activated hydrotalcite catalyst: Effects of reaction conditions

Continuous isomerization of glucose to fructose using activated hydrotalcite catalyst: Effects of reaction conditions

A Shapeshifting Roadmap for Polycyclic Skeletal Evolution.

Polycyclic ring systems are ubiquitous three-dimensional (3D) structural motifs central to the function of many biologically active small molecules and organic materials. Indeed, subtle changes to the overall molecular shape and connectivity of atoms in a polycyclic framework (i.e., isomerism) can drastically alter its function and properties. Unfortunately, direct evaluation of these structure-function relationships typically requires the development of distinct synthetic strategies toward a specific isomer. Dynamic, "shapeshifting" carbon cages present a promising approach for sampling isomeric chemical space but are often difficult to control and are largely limited to thermodynamic mixtures of positional isomers about a single core scaffold. Here, we describe the development of a new shapeshifting C9-chemotype and a chemical blueprint for its evolution into structurally and energetically diverse isomeric ring systems. By leveraging the unique molecular topology of π-orbitals interacting through-space (homoconjugation), a common skeletal ancestor evolved into a complex network of valence isomers. This unusual system represents an exceedingly rare small molecule capable of undergoing controllable and continuous isomerization processes through the iterative use of just two chemical steps (light and organic base). Computational and photophysical studies of the isomer network provide fundamental insight into the reactivity, mechanism, and role of homoconjugative interactions. Importantly, these insights may inform the rational design and synthesis of new dynamic, shapeshifting systems. We anticipate this process could be a powerful tool for the synthesis of structurally diverse, isomeric polycycles central to many bioactive small molecules and functional organic materials.

Isomerization of Glucose‐to‐Fructose in Water over a Continuous Flow Reactor using Ca−Al Mixed Oxide as Heterogeneous Catalyst

AbstractThis work reports the continuous isomerization of glucose to fructose in aqueous media under mild conditions using a mixed oxide hydrotalcite‐derived catalyst based on Ca and Al. Different operational parameters of the continuous flow fix‐bed catalytic reactor system were studied. At the optimal conditions, the Ca−Al‐based catalyst achieved a very high conversion and almost quantitative selectivity towards fructose, this being one of the few successful examples of a heterogeneous catalyst capable of carrying out this reaction in a continuous process. Importantly, catalytic activity held steady during four hours on stream, and slight deactivation occurring could be practically overcome by thermal regeneration of the catalyst.

Efficient Continuous Production of Lactulose Syrup by Alkaline Isomerization Using an Organogermanium Compound.

Lactulose, a keto-type disaccharide widely used in pharmaceuticals and functional foods, is produced by the isomerization of lactose. The organogermanium compound poly-trans-[(2-carboxyethyl) germasesquioxane] (Ge-132) is an effective reaction promoter for the conversion of lactose to lactulose because of its high affinity to ketoses. Herein, an effective method for the continuous production of lactulose syrup was developed using Ge-132 through the alkaline isomerization of lactose in a bench-scale plant. This plant carried out a continuous isomerization process using Ge-132, continuous two-step separation process for separating the sugar and Ge-132, a continuous purification and concentration processes for the lactulose syrup, and separation and purification processes for the recovery of Ge-132. In this bench-scale plant, lactulose-containing syrup (350 g/L lactulose, 92 g/L lactose, and 31 g/L galactose) was prepared. The syrup was produced at a rate of 37.7 mL/h, and the content of residual Ge-132 in the syrup was 2 mg/L. The separation process was a two-step separation system requiring an ordinary electrodialyzer and an electro deionizer, which allowed the separation of more than 99.6 % Ge-132 from the reaction mixture. Moreover, the majority of Ge-132 and sodium hydroxide were recovered through electrodialysis using a bipolar membrane. The proposed system is the first to represent the novel development of an effective continuous production system for lactulose-containing syrup on the basis of the use of organogermanium compounds and incorporation of the electrodialysis technology.

Remote and reversible control of in vivo bacteria clustering by NIR-driven multivalent upconverting nanosystems

Achieving remote and reversible control of bacterial cell-cell interactions associated with interference with pathological processes in living systems remains a challenge owing to the complexity of the in vivo microenvironment and the lack of regulation systems. We present, for the first time, the development of a versatile platform to achieve NIR-driven reversible bacterial clustering both in vitro and in vivo. This platform consisted of β-CD modified UCNP (UCNP-CD) and photochromic azobenzene glycoconjugates (azo-man), which could dynamically display d-mannose bioactive ligands. Specifically, by virtue of the noncovalent yet strong multivalent interactions between bacteria and nanosystems, robust bacterial clusters could be formed even in vivo within 1 h. Upon NIR stimulation, the upconverted emissions from UCNPs triggered the continuous isomerization of azo-man, leading to dissociation of the nanosystems and dispersion of bacterial clusters. Moreover, in vivo pathogenic infection process could be interfered with the NIR-switched bacterial agglutination. Most importantly, the noninvasive and deep-tissue-penetrating nature of NIR made it possible for dynamically regulation of cellular interactions with minimized influence to both normal cells and nature bacteria flora. This strategy would bring new perspectives for anti-virulence therapeutics and in-depth investigations of specific physiological phenomena.

Regeneration of a supported Nafion® catalyst for the double-bond isomerization of octadecenes

We studied solvent-based regeneration techniques on a commercial Nafion/SiO2 catalyst (SAC-13®, BASF). The test reaction was the double-bond isomerization of octadecenes, which are used in paper sizing agents and drilling fluids. The spent catalyst deactivated from surface coverage of octadecenes and higher-molecular weight oligomers. Polar and nonpolar solvents were tested in both batch and continuous regenerations. Up to 71% of the pore volume and 67% of the surface area were recovered, in the mesoporous regime. Batch and continuous isomerization experiments showed that a threshold quantity of oligomer must be removed, otherwise the activity of the regenerated catalysts does not correlate well with residual oligomer or the acid site concentration, because some solvents could not be completely displaced. The most effective solvent was m-xylene. Some acid sites were never recovered. Diffusional limitations and faster deactivation resulted in lower turnover frequencies in regenerated catalysts, in part due to decreased pore volume and in part because residual oligomer reacted with fresh monomer, such that fewer oligomerization events were necessary to close the pores in subsequent tests.

酵素法によるデンプンの高度変換利用技術の開発

This review summarizes three main topics from my work on enzyme application for starch processing, which is a major field of research in the development of industrial applications for enzymes. I have engaged in such research for more than 50 years, beginning in 1951 while I was with the enzyme production department of Nagase Co., Ltd. The first problem was the complete liquefaction of sweet potato suspension at high concentration using an enzyme process. With the “gradual heating method, ” a conventional method of liquefaction, the saccharified solution became turbid and it was impossible for the solution to be filtered and purified. The turbid liquid was generated by means of rearrangement of starch molecular chains that were not digested by enzymes in the process of gradual warm-up liquefaction. For the insoluble starch particles to be digisted, they had to be treated by heat at more than 120°C and have enzymes added again. As a liquefaction method to prevent generating insoluble starch particles, I developed the “Instantaneous heating method.” With this method, a starch suspension is instantaneously heated to 88-92°C with a-amylase. Since the method was inadequate for corn starch, double liquefaction was employed for the corn starch so that α-amylase could be added again after heating the starch solution at over 120°C. As thermostable α-amylase was produced and available from B. subtilis MK 385, the problem with corn starch liquefaction was solved by instantaneously heating at 100-110°C with a jet cooker. The second topic was the industrial production of glucose using an enzyme process. I started industrial production of glucoamylase originating from Aspergillus or Rhizopus and developed a saccharification method for starch to obtain 95-96% yield of glucose. The third problem was the development of isomerization from glucose to fructose. Glucose isomerase originating from Streptmyces phaeocromogenus was accumulated within a strain pellet. The cell with the enzyme was immobilized by an anion exchange resin modified with quaternary pyridine. It formed granulations, and cross-linked to boost its physical strength. Thus, continuous isomerization was developed with a tubular flow bioreactor packing the immobilized cell and production of glucose/fructose syrup as an alternative sweetening to sucrose was started.

Teratogenicity of isotretinoin revisited: Species variation and the role of all-trans-retinoic acid

This paper reviews the teratogenicity of isotretinoin in regard to aspects of species variation, toxicokinetics, and metabolism. Particular emphasis is given to the hypothesis that most effects of isotretinoin (13-cis-retinoic acid) are mediated by isomerization to the all-trans-retinoic acid. This mechanism of action would provide a basis for the understanding of species differences and the extrapolation of experimental results to the human situation and thus improve drug development. The insensitive species (rat, mouse) eliminate the drug rapidly through detoxification to the β-glucuronide; also, placental transfer is limited in these species. On the other hand, in sensitive species (primates), the drug is predominantly metabolized to the active 13-cis-4-oxo-retinoic acid; placental transfer is more extensive here. The β-glucuronides showed limited placental transfer in all species examined; these metabolites exhibited very low, if any, measurable concentrations in the human. The 13-cis-retinoic acid is not appreciably bound to cellular retinoid-binding proteins or nuclear receptors and exhibits low tissue distribution and placental transfer. Its access to the nucleus may be extensive. Because of the long half life of 13-cis-retinoic acid, continuous isomerization results in significant area under the concentration-time curve levels of all-trans-retinoic acid in the mouse, monkey and the human; the all-trans-retinoic acid formed is extensively distributed across the placenta and may be an important factor that contributes to the teratogenic potency of 13-cis-retinoic acid. Isomerization cannot explain the teratogenic effects of 13-cis-retinoic acid in the rat and rabbit. It is concluded that the high teratogenic activity of isotretinoin in sensitive species (human, monkey) is related to slow elimination of the 13-cis-isomer, to metabolism to the 4-oxo-derivative, to increased placental transfer, to continuous isomerization and significant exposure of the target tissue to all-trans-retinoic acid; and to lack of binding to cytoplasmic retinoid binding proteins that could possibly result in ready access to the nucleus. (J Am Acad Dermatol 2001;45:S183-7.)

Fructose production by immobilizedArthrobacter cells

ImmobilizedArthrobacter cells (NRRL-B-3728) were used for continuous isomerization of glucose to fructose in a bioreactor system. The system utilized stationary phase (55h) cells (2.2×109 CFU/ml saline) immobilized onto K-carrageenan (3% w/v) beads [cells were heated at 65°C for 10 min to inactivate endogenous proteolytic enzymes]. Immobilized-cell preparations were hardened using three different glutaraldehyde systems. Glutaraldehyde (0.2 M) treated-immobilized cells (pH 7.0, 5°C for 30 min) exhibited good gel strength and high glucose isomerase activities. Maximal bioreactor isomerization of 44% was achieved when a buffered feedstock containing 40% glucose was fed into the column (60°C) at a flow rate of 0.2 ml/min. The biological half-life of glucose isomerase activities in this system was 400 h. Scanning electron microscopy revealed large numbers of cells distributed within the beads. A thin layer surrounding the beads following glutaraldehyde treatment was mainly due to cross-linking reactions between cell proteins and glutaraldehyde. This layer prevented leaking of cells during continuous isomerization reaction.

Sugar cane bagasse as a possible source of fermentable carbohydrates. II. Optimization of the xylose isomerase reaction for isomerization of xylose as well as sugar cane bagasse hydrolyzate to xylulose in laboratory‐scale units

Both the forward and backward reactions of xylose isomerase (Sweetzyme Q) with xylose and glucose as substrates have been studied in terms of kinetics and thermodynamics. The relationship between the two reactions can thus be determined. Much attention has been given to the reaction with xylose as substrate. The optimal conditions of the xylose reaction in terms of pH, buffer, metal ions, substrate concentration, temperature, and ionic strength have been determined. These findings did not differ much from those reported for the glucose reaction. Equilibrium constants for the aldose to ketose conversion were more favorable in the case of glucose. The results obtained with continuous isomerization of xylose in columns packed with either Sweetzyme Q or Taka-Sweet were very similar to those obtained from batch isomerization processes. Particle size had a definite effect on reaction rate, which indicates that diffusion limitations do occur with the immobilized enzyme particles. Heat stability of Sweetzyme Q was good with t(1/2) of 118, 248, and 1200 h at 70, 55, and 40 degrees C, respectively. A novel method for the separation of xylose-xylulose mixtures with water as eluant on a specially prepared Dowex 1 x 8 column was developed. This technique has the capability of producing pure xylulose for industrial or research applications. A writ for a patent regarding this technique is at present prepared.

Immobilization of glucose isomerase

AbstractThe immobilization of glucose isomerase (D‐xylose ketol isomerase, EC 5.3.1.5) by covalently bonding to various carriers and by adsorption to ion exchange resins was attempted in order to obtain a stable immobilized enzyme which can be used for continuous isomerization of glucose in a column.Of the covalent bonding methods, the colloidal silica‐glutaraldehyde method showed the highest binding capacity and gave the stablest immobilized glucose isomerase. The LUDOX HS‐30 bound glucose isomerase column showed a half‐life of 24 days and an enzyme usage of 0.07 units per gram of isomerized sugar (d.s., fructose 45%).Of the resins used, the macromolecular type or porous type strongly basic anion exchange resins showed the highest binding capacity and gave the stablest immobilized glucose isomerase. The Amberlite IRA‐904 resine‐bound glucose isomerase showed a half‐life of 23 days and an enzyme usage of 0.06 units per gram of isomerized sugar (d. s., fructose 45%).Based on the ease of the immobilization process, the possibility of carrier ruse the extensive use already achieve by ion exchange resins in the sugar industry, IRA‐904 resin was selected as the candidate for commercialization.

Immobilization of glucose isomerase.

The immobilization of glucose isomerase (D-xylose ketol isomerase, EC 5.3.1.5) by covalently bonding to various carriers and by adsorption to ion exchange resins was attempted in order to obtain a stable immobilized enzyme which can be used for continuous isomerization of glucose in a column. Of the covalent bonding methods, the colloidal silica-glutaraldehyde method showed the highest binding capacity and gave the most stable immobilized glucose isomerase. The Ludox HS-30 bound glucose isomerase column showed a half-life of 24 days and an enzyme usage of 0.07 units per gram of isomerized sugar (d.s, fructose 45%). Of the resins used, the macromolecular type or porous type strongly basic anion exchange resins showed the highest binding capacity and gave the most stable immobilized glucose isomerase. The Amberlite IRA-904 resine-bound glucose isomerase showed a half-life of 23 days and an enzyme usage of 0.06 units per gram of isomerized sugar (d.s., fructose 45%). Based on the ease of the immobilization process, the possibility of carrier reuse and the extensive use already achieved by ion exchange resins in the sugar industry, IRA-904 resin was selected as the candidate for commercialization.

Immobilization of Glucose Isomerase on Radiation‐Modified Gelatine Gel

AbstractWhole‐cell glucose isomerase immobilization on radiation‐modified gelatine gel was demonstrated. The enzyme was stabilized within the cells by heat‐treatment at 70°C. The heat‐treated cells were mixed with radiation‐modified gelatine gel and cross‐linked by glutaraldehyde. Immobilized enzyme exhibited 70–75% activity as compared to the free cells. Several properties of immobilized glucose isomerase were studied under various reaction conditions. A continuous isomerization was performed using a column packed with cell granules. It has been found, that the half‐life of the immobilized glucose isomerase amounted to 650 h at 60°C.

Purification, Immobilization, and Some Properties of Glucose Isomerase from Streptomyces flavogriseus

Glucose isomerase (EC 5.3.1.5) produced from Streptomyces flavogriseus was purified by fractionation with (NH(4))(2)SO(4) and chromatography on diethylaminoethyl (DEAE)-cellulose and DEAE-Sephadex A-50 columns. The purified enzyme was homogeneous as shown by ultracentrifugation and sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Benzyl DEAE-cellulose, triethylaminoethyl-cellulose, and DEAE-cellulose were effective in the immobilization of partially purified glucose isomerase. Several differences in properties were found between purified soluble enzyme, immobilized enzyme (DEAE-cellulose-glucose isomerase), and heat-treated whole cells. Glucose and xylose served as substrate for the enzyme. Whole cells had the highest K(m) values for glucose and xylose; the soluble enzyme had the lowest values. The optimum temperature for activity of the soluble and immobilized enzymes was 70 degrees C; that for whole cells was 75 degrees C. The pH optimum for the three enzyme preparations was 7.5. Magnesium ion or Co was required for enzyme activity; an addition effect resulted from the presence of both Mg and Co. The enzyme activity was inhibited by Hg, Ag, or Cu. The conversion ratio of the enzyme for isomerization was about 50%. The soluble and immobilized enzymes showed a greater heat stability than whole cells. The soluble enzyme was stable over a slightly wider pH (5.0 to 9.0) range than the immobilized enzyme and whole cells (pH 5.5 to 9.0). The molecular weight of the enzyme determined by the sedimentation equilibrium method was 171,000. A tetrameric structure for the enzyme was also indicated. After operating at 70 degrees C for 5 days, the remaining enzyme activity of the immobilized enzyme and whole cells, which were used for the continuous isomerization of glucose in a plug-flow type of column in the presence of Mg and Co, was 75 and 55%, respectively. Elimination of Co decreased operational stability.

Practical Process Conditions for the Use of Immobilized Glucose Isomerase

AbstractThe present world‐wide rush into the production of high fructose corn syrups has increased the demand for the enzym glucose isomerase for the isomerization process. Economics have forced producers of these sweeteners to use the immobilized enzyme in a continuous process. The most suitable way of performing continuous isomerization turned out to be a process in a fixed‐bed column. However, a downflow mode of the substrate through the enzyme bed required special properties of the beads, especially when using very high enzyme beds.Practical process conditions are described for the use of immobilized Maxazyme glucose isomerase in a continuous fixed‐bed column operation procedure, e. g. pH, temperature, concentration of activators, quality of the substrate and enzyme bed dimensions. Special attention is paid to compressibility of the enzyme particles and the characteristical pressure drop of this product. Improvements are described for the production of this immobilized enzyme, which make it possible to use Maxazyme Gl‐Immob in columns up to 5 m bed height.

Immobilization of Glucose Isomerase in Microbial Cells. Part 1. Preparation of Cell Granules and their Enzyme Retentivities

AbstractAn immobilization method for glucose isomerase in microbial cells was demonstrated, in which cells derived from Streptomyces sp. were aggregated with chitosan and cross‐linked with bifunctional reagents. Enzyme retentivity of the product was investigated in relation to the enzyme activity change during cell treatment. The reaction conditions with glutaraldehyde, i.e. the reagent concentration, reaction time and pH of the reaction solution were examined. The effect of gelatin glue addition to cell granule formation on the binding toughness of the product was also investigated. Swelling capacity of the granule was observed to be restrained by cross‐linking. A continuous isomerization performance using a colum packed with cell granules was carried out.

Preparation and performance of cellulose bead-entrapped whole cell glucose isomerase

A novel simple and mild technique to entrap glucose isomerase activeA. missouriensis cells within α-cellulose beads has been developed. Regenerated α-cellulose beads were shown by SEM to be highly loaded with microbial cells. Kinetics, high operational stability, reactor performance, and low cost of carrier showed the entrapped cell preparation to be suitable for continuous isomerization of 45% glucose solution. This paper was presented at the 4th Enzyme Engineering Conference, Bad Neuenahr, Germany. Sponsored by the Engineering Foundation, New York, New York.

Use of Sweetzyme in Industrial Continuous Isomerization Various Process Alternatives and Corresponding Product Types

AbstractSince Novo's immobilized glucose isomerase, Sweetzyme, was presented at the 26th Starch Convention in Detmold in 1975, a rapid development has taken place. Up‐scaling led to two alternatives for the continuous isomerization process: Fixed‐bed and expanded‐bed.The most simple way to use the immobilized enzyme in a continuous process is in a fixed‐bed column, where high‐glucose syrup is usually pumped downwards through the enzyme bed. However, the pressure drop over the enzyme bed puts a limit to the capacity of each column, so usually a number of reactors have to be used, connected in series or in parallel. Development of mechanically stronger immobilized products has made it possible to operate even large capacity plants in a convenient manner and with a practical number of reactors.In the expanded‐bed lay‐out high‐glucose syrup is pumped upwards through the enzyme bed, with sufficient linear velocity to partly lift the enzyme particles and give an expansion of the bed. The enzyme particles with then be moving but will still touch each other. The pressure drop over the expanded‐bed is small, and does not limit reactor capacities. However, good flow distribution at the bottom of the reactor becomes of prevailing importance. For very large columns, a generally applicable design has not been developed as yet.In a number of countries high‐fructose syrup is today being made industrially by continuous processes, based on Sweetzyme.

Continuous Isomerization of Glucose to Fructose on a Commercial Basis

AbstractImmobilized glucose isomerase has been used to make more than 500,000 metric tons of high fructose corn syrups in the United States. These syrups have found wide application as high quality sweeteners to replace sucrose.A commercial process is described for the continuous enzymatic conversion of glucose to fructose. The use of immobilized glucose isomerase in a multiple bed reactor system is an economical method for making fructose. A comparison between immobilized glucose isomerase in a batch versus a continuous process shows the continuous process has the following advantages: Lower enzyme usage and cost for converting glucose to fructose. Lower capital equipment and labor costs. Better and easier process control. Lower refining costs and improved product quality. Both the continuous isomerization process and the immobilization technique described are developments of Clinton Corn Processing Company, a Division of Standard Brands, Inc.

Isomerization of Dextrose into Fructose by the Alkali Method. Part 2. Design and Installation of the Pilot Plant of the Continuous Isomerization and Determination of its Operating Conditions

Isomerization of Dextrose into Fructose by the Alkali Method. Part 2. Design and Installation of the Pilot Plant of the Continuous Isomerization and Determination of its Operating Conditions