Gene cloning and characterization of a thermostable phytase from Bacillus subtilis US417 and assessment of its potential as a feed additive in comparison with a commercial enzyme.
An extracellular phytase from Bacillus subtilis US417 (PHY US417) was purified and characterized. The purified enzyme of 41 kDa was calcium-dependent and optimally active at pH 7.5 and 55 degrees C. The thermal stability of PHY US417 was drastically improved by calcium. Indeed, it recovered 77% of its original activity after denaturation for 10 min at 75 degrees C in the presence of 5 mM CaCl2, while it retained only 22% of activity when incubated for 10 min at 60 degrees C without calcium. In addition, PHY US417 was found to be highly specific for phytate and exhibited pH stability similar to Phyzyme, a commercial phytase with optimal activity at pH 5.5 and 60 degrees C. The phytase gene was cloned by PCR from Bacillus subtilis US417. Sequence analysis of the encoded polypeptide revealed one residue difference from PhyC of Bacillus subtilis VTTE-68013 (substitution of arginine in position 257 by proline in PHY US417) which was reported to exhibit lower thermostability especially in the absence of calcium. With its neutral pH optimum as well as its great pH and thermal stability, the PHY US417 enzyme presumed to be predominantly active in the intestine has a high potential for use as feed additive.
Laboratoire d'Enzymes et de Métabolites des Procaryotes, Centre de Biotechnologie de Sfax, Route de Sidi Mansour Km 6, BP "1177", 3038 Sfax, Tunisia.
Ameny
A
Farhat
Hichem
H
Chouayekh
Mounira
M
Ben Farhat
Kameleddine
K
Bouchaala
Samir
S
Bejar
D010832:6-Phytase / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D000595:Amino Acid Sequence; D000821:Animal Feed; D001412:Bacillus subtilis / Q000201:enzymology*; D003001:Cloning, Molecular; D004795:Enzyme Stability; D005503:Food Additives; D006863:Hydrogen-Ion Concentration; D050296:Microbial Viability; D016415:Sequence Alignment; D013379:Substrate Specificity; D013696:Temperature
D005503:Food Additives; D010832:6-Phytase