Microbial glucoamylases: characteristics and applications

Abstract

Glucoamylase is one of the oldest and widely used biocatalysts in food industry. The major application of glucoamylase is the saccharification of partially processed starch/dextrin to glucose, which is an essential substrate for numerous fermentation processes and a range of food and beverage industries. Glucoamylase for commercial purposes has traditionally been produced employing filamentous fungi, although a diverse group of microorganisms is reported to produce glucoamylase, since they secrete large quantities of the enzyme extracellularly. The commercially used fungal glucoamylases have certain limitations such as moderate thermostability, acidic pH requirement, and slow catalytic activity that increase the process cost. Consequently, the search for newer glucoamylases and protein engineering to improve pH and temperature optima leading to amelioration in catalytic efficiency of existing enzymes have been the major areas of research over the years. The present review focuses attention on the recent advances in molecular biology and protein engineering of glucoamylase to improve its production and functional properties including the so far success achieved in isolating mutants with enhanced thermostability and selectivity, higher pH optimum and improved catalytic activity. A comprehensive account is included on the diversity, regulation of production, classification, purification and properties, and potential applications of microbial glucoamylases to provide an overview on all the important aspects of the enzyme.

Purification and characterization of a novel α-glucosidase from an Antarctic yeast Dioszegia fristingensis isolate

“…Although D. fristingensis is a psychrotolerant yeast having an optimal growth temperature at 15°C, its secreted α-glucosidase exhibit the best activity at 37-40°C having its K m value on soluble starch of 1.3 g/L. This K m value is in the range typical for microbial α-amylases and glucoamylases described to be best active at 40-50°C, but is lower than that for the enzymes with optimal activity above 60°C [13,[48][49][50]. In relation to thermal inactivation of the α-glucosidase from D. fristingensis, its decimal reduction time at 30°C, 40°C and 50°C was 12.5, 10.5 and 7 h, respectively.…”

“…The reported molecular weight for fungal amylolytic enzymes is wide variable ranging from 27 to 250 kDa, and the majority of them are glycosylated [13,38]. Glycosylation is a posttranslational modification present in almost all excreted eukaryotic polypeptides and important for protein exporting, folding and biological activity [39].…”

“…For its part, several α-glucosidases and glucoamylases from mesophilic bacteria, fungi and yeasts have been described, which, in general, display optimal activity at temperatures up to 45°C and at acidic pH [21][22][23]. The mostly used α-glucosidases and glucoamylases in industrial processes have been obtained from Aspergillus species with major activity displayed at temperatures between 45-60°C [13,24,25]. Currently, the search for novel microbial sources of amylases with high activity at low temperatures, for energy-saving, gains importance.…”

Chromatography as the Major Tool in the Identification and the Structure-Function Relationship Study of Amylolytic Enzymes from Saccharomycopsis Fibuligera R64

“…α-Amylase is commonly used in food, beverage, paper industries (8), in textile industry and as additive in detergents (9,10), for renewable energy (11,12) and medical purpose (13). Glucoamylase has been the most important enzyme in food industry, mainly in the production of sugar or ethanol (14). Glucoamylase is normally employed in combination with amylolytic enzymes that are able to act on more complex polysaccharides, such as α-…”

Protein Engineering Methods and Applications

“…Screening organic solvent-tolerant bacteria or extremophiles has been preferred to isolate and improve naturally solvent-stable enzymes (Gupta & Khare, 2009;Doukyu & Ogino, 2010). Other protein engineering examples with industrially and/or pharmacologically important enzymes include studies on cholesterol oxidase (Pollegioni et al, 2009), cyclodextrin glucanotransferases (Leemhuis et al, 2010), human butyrylcholinesterase (Masson et al, 2009), microbial glucoamylases (Kumar & Satyanarayana, 2009), lipases of different origins (Akoh et al, 2004;Verma et al, 2008;Kurtovic et al, 2009), phospholipases (Song et al, 2005;De Maria et al, 2007;Simockova & Griac, 2009) and phytases (Rao et al, 2009). Studies on extremozymes, enzymes isolated from extremophilic species, revealed their different structural and functional characteristics which could be exploited for biotechnological applications and improved further by protein engineering (Bjarnason et al, 1993;Hough & Danson, 1999;Georlette et al, 2004).…”