Enzymatic Isomerization Of Glucose Research Articles

Aluminum‐Containing Metal‐Organic Frameworks as Selective and Reusable Catalysts for Glucose Isomerization to Fructose

AbstractFructose is a versatile precursor for food and chemicals. Currently, catalytic production of fructose is achieved by enzymatic isomerization of glucose from renewable lignocellulose. Although the catalyst, glucose isomerase, is selective, it is not stable. Here, aluminum‐containing metal‐organic frameworks (Al‐MOFs) are shown to be active, selective, stable, and reusable for glucose isomerization in ethanol. Al‐MOFs achieved 64% fructose selectivity with 82% glucose conversion at 120 °C, superior performance compared with most other solid catalysts. The amino groups in Al‐MOFs enhance Lewis acid strength, which is responsible for the high fructose selectivity at high glucose conversion. Moreover, the Al‐MOF catalyst is stable and reusable at least four times without losing either activity or fructose selectivity. These findings illustrate compelling opportunities for Al‐MOFs in fructose production and other organic reactions, such as fructose conversion to 5‐hydroxymethylfurfural and levulinic acid.

Enzymatic isomerization of glucose and xylose in ionic liquids

Glucose isomerase has been found for the first time to catalyze the isomerization of glucose to fructose in the ionic liquid N,N-dibutylethanolammonium octanoate (DBAO). Isomerization was achieved at temperatures of 60–80 °C although a substantial amount of mannose was formed at elevated temperatures via the Lobry-de Bruyn–van Ekenstein transformation. Complete recovery of the sugars after reaction was achieved by extraction with aqueous HCl, thus making the protocol attractive for continuous operation.

Optimization of Operating Temperature for Continuous Immobilized Glucose Isomerase Reactor with Pseudo Linear Kinetics

AbstractIn this work, the optimal operating temperature for the enzymatic isomerization of glucose to fructose using a continuous immobilized glucose isomerase packed bed reactor is studied. This optimization problem describing the performance of such reactor is based on reversible pseudo linear kinetics and is expressed in terms of a recycle ratio. The thermal deactivation of the enzyme as well as the substrate protection during the reactor operation is considered. The formulation of the problem is expressed in terms of maximization of the productivity of fructose. This constrained nonlinear optimization problem is solved using the disjoint policy of the calculus of variations. Accordingly, this method of solution transforms the nonlinear optimization problem into a system of two coupled nonlinear ordinary differential equations (ODEs) of the initial value type, one equation for the operating temperature profile and the other one for the enzyme activity. The ODE for the operating temperature profile is dependent on the recycle ratio, operating time period, and the reactor residence time as well as the kinetics of the reaction and enzyme deactivation. The optimal initial operating temperature is selected by solving the ODEs system by maximizing the fructose productivity. This results into an unconstrained one‐dimensional optimization problem with simple bounds on the operating temperature. Depending on the limits of the recycle ratio, which represents either a plug flow or a mixed flow reactor, it is found that the optimal temperature of operation is characterized by an increasing temperature profile. For higher residence time and low operating periods the residual enzyme activity in the mixed flow reactor is higher than that for the plug flow reactor, which in turn allows the mixed flow reactor to operate at lower temperature than that of the plug flow reactor. At long operating times and short residence time, the operating temperature profiles are almost the same for both reactors. This could be attributed to the effect of substrate protection on the enzyme stability, which is almost the same for both reactors. Improvement in the fructose productivity for both types of reactors is achieved when compared to the constant optimum temperature of operation. The improvement in the fructose productivity for the plug flow reactor is significant in comparison with the mixed flow reactor.

Optimal temperature policy for immobilized enzyme packed bed reactor performing reversible Michaelis-Menten kinetics using the disjoint policy.

The optimal temperature policy that maximizes the time-averaged productivity of a continuous immobilized enzyme packed bed reactor is determined. This optimization study takes into consideration the enzyme thermal deactivation with substrate protection during the reactor operation. The general case of reversible Michaelis-Menten kinetics under constant reactor feed flow rate is assumed. The corresponding nonlinear optimization problem is solved using the calculus of variations by applying the disjoint policy. This policy reduces the optimization problem into a differential-algebraic system, DAE. This DAE system defines completely the optimal temperature-time profiles. These profiles depend on the kinetic parameters, feed substrate concentration, operating period, and the residence time and are characterized by increasing form with time. Also, general analytical expressions for the slopes of the temperature and residual enzyme activity profiles are derived. An efficient solution algorithm is developed to solve the DAE system, which results into a one-dimensional optimization problem with simple bounds on the initial feed temperature. The enzymatic isomerization of glucose into fructose is selected as a case study. The computed productivities are very close to that obtained by numerical nonlinear optimization with simpler problem to solve. Moreover, the computed conversion profiles are almost constant over 90% of the operating periods, thus producing a homogeneous product.

Comparison of the enzymatic isomerization of glucose produced by porcine serum .ALPHA.-glucosidase and Rhizopus glucoamylase.

Etude de la stereospecificite de la glucose isomerase dans la reaction glucose-fructose. Pour cela, on compare les actions des associations d'enzymes (α glucosidase porcine-glucoisomerase de Streptomyces) et (glucoamylase de Rhizopus-glucoisomerase de Streptomyces) sur la saccharification/isomerisation du maltohexaose

Conversion of Glucose in Lactase-Hydrolyzed Whey Permeate to Fructose with Immobilized Glucose Isomerase

The maximum conversion of glucose to fructose in lactase-hydrolyzed whey permeate by glucose isomerase was approximately 52% at .1g enzyme/ml substrate after 7h incubation at 60°C. Removal of minerals from the substrate was essential for enzyme activity. The dependence of the enzyme on Mg++ and Co++ for activity in the presence of high ash concentration was demonstrated. Optimum Mg++ and Co++ additions were 250 and 100ppm, respectively. The isomerization reaction was enhanced more when both 100ppm Mg++ and 50ppm Co++ were added. Hydrolyzed isomerized lactose whey syrup with sweetness equivalent to sucrose was successfully produced through enzymatic isomerization of glucose in lactase-hydrolyzed whey permeate after supplementation with pure glucose. Fructose in hydrolyzed isomerized lactose whey syrup was effectively separated from other sugars by Dowex 1X8-200 anion exchange resin in the bisulfite form.