African Journal of
Biotechnology

  • Abbreviation: Afr. J. Biotechnol.
  • Language: English
  • ISSN: 1684-5315
  • DOI: 10.5897/AJB
  • Start Year: 2002
  • Published Articles: 12209

Full Length Research Paper

Isolation and characterization of a haloalkaliphilic protease producer bacterium from Wadi Natrun in Egypt

Walid Ahmed Lotfy
  • Walid Ahmed Lotfy
  • Microbiology Department, Faculty of Dentistry, Pharos University in Alexandria, Egypt.
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Neveen Mohamed Abd-El-Karim
  • Neveen Mohamed Abd-El-Karim
  • Botany and Microbiology Department, Faculty of Science, Alexandria University, Egypt.
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Ebaa Ebrahim El-Sharouny
  • Ebaa Ebrahim El-Sharouny
  • Botany and Microbiology Department, Faculty of Science, Alexandria University, Egypt.
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Ehab Ragheb El-Helow
  • Ehab Ragheb El-Helow
  • Botany and Microbiology Department, Faculty of Science, Alexandria University, Egypt.
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  •  Received: 10 March 2017
  •  Accepted: 28 April 2017
  •  Published: 24 May 2017

Abstract

A Gram-positive, rod-shaped, spore-forming haloalkaliphilic bacterium designated as NA7 was isolated from the surface of a Helianthemum nummularium root sample obtained from Wadi Natrun in Egypt. Sequence analysis of the 16S rRNA gene revealed a Bacillus haloalkaliphilius strain as the closest match with 99% identity. In a shake flask culture containing 10% NaCl, adjusted to pH 10 and incubated at 37°C, the isolated strain produced thermostable extracellular alkaline protease with relatively stable maximum activity records (0.610-0.625 TU) within a relatively long stationary phase that exceeded 60 h. A 2-level fractional factorial design (Plackett-Burman) was then applied to screen for nutritional and cultivation factors regulating protease production by the isolate and to appraise their effects. Calculated statistical parameters revealed that NaCl and MgSO4 are the most significant independent variables affecting alkaline protease production by NA7 and suggested a near-optimum culture condition. Verification of this predicted condition resulted in an alkaline protease specific activity record of 509 TU/mg protein with a 1.27 fold increase when compared to the basal medium culture.

 

Key words: Alkaline protease, Bacillus haloalkaliphilus, Wadi Natrun, haloalkaliphiles.