Abstract:
A starch degrading bacterial isolate 64G3 was taxonomically
characterized. Based on physiological properties, 16S rDNA sequence analysis
and DNA-DNA hybridization, this isolate was assigned to Petrotoga mexicana
species. A gene encoding an α-amylase of this strain was cloned and overexpressed
in Escherichia coli. The gene is 1, 992 bp long encoding a polypeptide
of 663 amino acids with a calculated molecular mass of 77, 042 Da. The deduced
amino acids sequence shows a high identity of 94% with Petrotoga mobilis
SJ95 α-amylase but low identities (up to 45%) with other glycosyl hydrolase
family 13 enzymes. Recombinant amylase produced in Escherichia coli showed
hydrolytic activity towards amylose, amylopectin, glycogen and maltooligosaccharides
but not pullulan or other types of cyclodextrins. The optimal temperature and
pH for the enzyme activity on starch were 45°C and 6.5, respectively. The
enzyme cleaved soluble starch in endo-acting manner to release maltose, maltotriose
and a minor amount of glucose during hydrolysis.
H-Cuong Le, N-Hai Truong and Thomas Schweder, 2012. Characterization of the Thermophilic Starch Degrading Petrotoga Strain 64G3 and the Expression of its α-amylase Gene. Biotechnology, 11: 199-208.
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