Glucoamylase

Glucoamylase, also called amyloglucosidase, is an exo-acting glycoside hydrolase (EC 3.2.1.3) that hydrolyzes starch by progressively removing glucose units from the nonreducing ends. It cleaves both α-1,4 and, to a lesser extent, α-1,6 glycosidic bonds, yielding primarily glucose molecules. Unlike alpha-amylase, which cleaves internal linkages to produce shorter oligosaccharides, glucoamylase acts from the chain ends.

In nature and industry, glucoamylases are produced mainly by fungi such as Aspergillus niger and Aspergillus awamori during solid- or submerged fermentation. Bacterial and yeast sources also exist, and recombinant forms are used to meet industrial demand. Commercial preparations are typically glycosylated enzymes formulated for starch-hydrolysis processes.

Optimal conditions vary by source but typical fungal glucoamylases have acidic to neutral pH optima (about pH 4–6) and thermostable versions function best near 60–70°C. Enzymatic activity can be inhibited by high glucose concentrations (product inhibition). Glucoamylases are often used with alpha-amylases to maximize starch conversion.

Applications include production of glucose-rich syrups from starch for food and beverage industries, brewing and beer mashing, and fermentation-based biofuel production. They are also used in baking and as digestive aids in some dietary supplements. The enzyme’s ability to convert starch to glucose makes it central to starch processing and sweetener manufacture.