glucoamilase

Glucoamylase, also called amyloglucosidase, is an extracellular enzyme that hydrolyzes the glycosidic bonds in starch and related polysaccharides, releasing glucose units from the non-reducing ends. It acts processively on the chains, primarily cleaving alpha-1,4 linkages and, to a lesser extent, alpha-1,6 linkages. The enzyme generally operates under acidic conditions (pH around 4–5) and at moderate temperatures, with industrial variants developed for improved thermostability.

Natural producers include filamentous fungi such as Aspergillus niger and Aspergillus oryzae, as well as certain bacteria and yeasts. Industrial glucoamylases are produced by fermentation of these organisms or by recombinant expression in microbial hosts, then purified and formulated for use in starch-processing applications. The choice of production organism influences properties such as pH and temperature optima, as well as tolerance to process inhibitors.

Mechanistically, glucoamylase is an exo-acting enzyme that cleaves glucose units from the ends of starch chains, enabling complete saccharification to glucose. Many fungal glucoamylases possess a starch-binding domain that helps target granules of starch, enhancing activity on granular substrates. Enzyme stability varies among sources, and thermostable variants enable faster processing at higher temperatures, reducing viscosity and improving throughput.

Applications include the conversion of starch to glucose syrups in the food and beverage industry, where glucoamylase is used with alpha-amylase to achieve efficient liquefaction and saccharification. It is also employed in baking to improve fermentation and sweetness, in brewing and distilling, and in biofuel production to generate fermentable sugars. In some enzyme preparations, it is combined with other carbohydrases to optimize yields.

Safety and regulation: Glucoamylases used in food processing are commonly approved as processing aids in many jurisdictions, produced from approved strains and subject to purity standards and labeling requirements. They are typically considered safe when used as directed.