Fungal Glucoamylase Production and Characterization: A Review

Fungal enzymes are preferred over other microbial sources owing to their widely accepted Generally Regarded As Safe (GRAS) status. Glucoamylase (GA) is an exohydrolase, which releases β-glucose units from the nonreducing ends of starch and used in the manufacture of glucose, fructose syrups and other industrial purposes. They can be produced from various substrates by different methods, including submerged, semi-solid and solid- state fermentation processes. Optimum production of glucoamylase was observed in previous studies at a range of pH from 4.0 to 5.0 and temperature 30 to 40°C with the incubation period of 4 to 5 days. Optimum catalytic activity was also recorded in previous experimental studies at a wide range of pH 4 to 8 and temperature 40 to 70°C. In previous literature, it was observed that most of the fungi produced several isoenzymes that had different molecular weights ranges from 40 to 125 kDa. The majority of fungal glucoamylase was multidomain consisting of the N-terminus catalytic domain (CD) and the C-terminus starch-binding domain (SBD). The catalytic domain folds as a twisted (α/α) 6-barrel containing a hex-helical hairpin toroidal structure while starch binding domain folds as an antiparallel β-barrel having two independent substrate binding sites. The present review focuses on recent findings on glucoamylase production, characteristics, structure, mechanism of action and industrial applications.