Glucose

Glucose, a simple monosaccharide sugar, is one of the most important carbohydrates and is used as a source of energy in animals and plants. Glucose is one of the main products of photosynthesis and starts respiration. The natural form (D-glucose) is also referred to as dextrose, especially in the food industry.

Commercial production

Glucose is prepared commercially via the enzymatic hydrolysis of starch. Many crops can be used as the source of the initial starch. Maize, rice, wheat, potato, cassava, arrowroot, and sago are all used in various parts of the world. In the United States, cornstarch (from maize) is used almost exclusively.

Related Topics:
Enzymatic - Hydrolysis - Starch - Maize - Rice - Wheat - Potato - Cassava - Arrowroot - Sago - United States - Cornstarch

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This enzymatic process has two stages. Over the course of 1–2 hours near 100 °C, these enzymes hydrolyze starch into smaller carbohydrates containing on average 5–10 glucose units each. Some variations on this process briefly heat the starch mixture to 130 °C or hotter one or more times. This heat treatment improves the solubility of starch in water, but deactivates the enzyme, and fresh enzyme must be added to the mixture after each heating.

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In the second step, saccharification, the partially hydrolyzed starch is completely hydrolyzed to glucose using the glucoamylase enzyme from the fungus Aspergillus niger. Typical reaction conditions are pH 4.0–4.5, 60 °C, and a carbohydrate concentration of 30–35% by weight. Under these conditions, starch can be converted to glucose at 96% yield after 1–4 days. Still higher yields can be obtained using more dilute solutions, but this approach requires larger reactors and processing a greater volume of water, and is not generally economical. The resulting glucose solution is then purified by filtration and concentrated in a multiple-effect evaporator. Solid D-glucose is then produced by repeated crystallizations.

Related Topics:
Glucoamylase - Fungus - Aspergillus niger - PH - Filtration - Multiple-effect evaporator - Crystallization

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