Glucose Isomerization by Enzymes

Abstract

Increasingly, the possibilities of using biomass due to climate change, depletion of fossil fuels, and the search for new renewable resources are being developed more and more. Lignocellulosic biomass is the structure of plants that includes waste from agriculture and forestry. Cellulose is a glucose-glucose polymer. In this study, we focus on glucose isomerization as one of the most commonly used processes for fructose production. Fructose is a product used both in the food industry for the preparation of sweeteners and in the production of biochemicals, being one of the main precursors for obtaining levulinic acid and high-added value products such as the 5-hydroxymethylfurfural (5-HMF). Although it requires an isomerization process to obtain fructose, the benefits of fructose over glucose far outweigh the costs involved in this transformation. There are different ways to catalyze the isomerization reaction, e.g. by using ion-exchange resins or enzymes as catalysts. In this study, we have worked with the glucose isomerase enzyme to investigate its optimum working conditions regarding pH and temperature. The feasibility of reusing this enzyme is also studied. All samples of the experiments performed were analyzed in a High Performance Liquid Chromatography (HPLC). In this study we have found two optimum working conditions: At a pH of 8.6 the optimum temperature is 70ºC and working at a pH of 7.6 the optimum temperature is at 80ºC. However, higher conversion is achieved by working with higher pH and at higher temperatures. But the stability of the enzyme must also be taken into account, which requires the presence of MgSO4·7H2O to stabilize the enzyme as has been demonstrated in the enzyme reuse’s experiments.