Properties of a Novel Thermostable Glucoamylase from the Hyperthermophilic Archaeon Sulfolobus solfataricus in Relation to Starch Processing

Abstract

A gene (ssg) encoding a putative glucoamylase in a hyperthermophilic archaeon, Sulfolobus solfataricus, was cloned and expressed in Escherichia coli, and the properties of the recombinant protein were examined in relation to the glucose production process. The recombinant glucoamylase was extremely thermostable, with an optimal temperature at 90°C. The enzyme was most active in the pH range from 5.5 to 6.0. The enzyme liberated ␤-D-glucose from the substrate maltotriose, and the substrate preference for maltotriose distinguished this enzyme from fungal glucoamylases. Gel permeation chromatography and sedimentation equilibrium analytical ultracentrifugation analysis revealed that the enzyme exists as a tetramer. The reverse reaction of the glucoamylase from S. solfataricus produced significantly less isomaltose than did that of industrial fungal glucoamylase. The glucoamylase from S. solfataricus has excellent potential for improving industrial starch processing by eliminating the need to adjust both pH and temperature.

Overexpression and characterization of an extremely thermostable maltogenic amylase, with an optimal temperature of 100 °C, from the hyperthermophilic archaeon Staphylothermus marinus

“…Many hyperthermophilic Archaea can degrade starch, and thus much effort has recently been directed toward characterizing their amylolytic enzymes. Highly thermostable starch-hydrolyzing enzymes from the genera Sulfolobus [5][6][7], Pyrococcus [8], and Thermococcus [9] have been described. These enzymes are interesting because of not only their biotechnological potential but also their use as models for studying hyperthermophilicity [10].…”

VapC6, a ribonucleolytic toxin regulates thermophilicity in the crenarchaeote Sulfolobus solfataricus

“…Simultaneous use of these genetic markers required construction of a strain (PBL2069) that was deficient in utilization of both lactose and maltose as sole carbon and energy sources (Table 2). Although Sso encodes six annotated a-glucosidases (She et al 2001;Kim et al 2004), deletion of only three was sufficient to create an absolute catabolic defect for maltose utilization. a-glucosidase-specific activities for several strains were measured to assess the relative importance of each of these genes.…”

“…Complementation of the vapB6TlacS disruption mutant depended on the development of a new genetic marker encoded by malA and a host strain that had lost the catabolic ability to grow on maltose. The S. solfataricus genome is thought to encode several a-glucosidases (Kim et al 2004). Deletion of three of these genes was sufficient to disable maltose catabolism and create a strong selection for restoration of this trait by malA introduction.…”

The Role of Extremophilic Microorganisms and their Bioproducts in Food Processing and Production

“…(Gill and Kaur, 2004), Clostridium sp. 0005 (Ohnishi et al, 1992), Thermomucor indicae-sendaticae (Satyanarayana et al, 2004), Thermoanaerobacter tengcongensis (Zheng et al, 2010) and the archaeal species Sulfolobus solfataricus (Kim et al, 2004), Thermoplasma acidophilum (Dock et al, 2008), Picrophilus torridus, and Picrophilus oshimae. The latter three archaeal species produce glucoamylases that are optimally active at pH 2 and 90 • C, with catalytic activity remaining at pH values as low as 0.5 and at 100 • C (Egorova and Antranikian, 2005).…”