African Journal of
Microbiology Research

  • Abbreviation: Afr. J. Microbiol. Res.
  • Language: English
  • ISSN: 1996-0808
  • DOI: 10.5897/AJMR
  • Start Year: 2007
  • Published Articles: 5232

Full Length Research Paper

Isolation and characterization of a psychrophilic bacterium producing cold active lactose hydrolyzing enzyme from soil of Mt. Himalaya in Nepal

E. S. Nam1, Y. H. Kim2, K. H. Shon2, and J. K. Ahn2*
1Department of Chemical and Biomolecular Engineering, Sogang University, Seoul 121-742, Republic of Korea. 2Department of Agricultural Sciences, Korea National Open University, Seoul 110-791, Republic of Korea.
Email: [email protected]

  •  Accepted: 18 February 2011
  •  Published: 18 July 2011


Psychrophilic bacteria, which grew on lactose as a carbon source, were isolated from soil of Island Peak area at Mt. Himalaya in Nepal, and identified. 148 bacterial isolates were isolated via X-gal hydrolysis on plate. Among these, three isolates, referred to as KNOUC 401, 402 and 403, displayed good cold-adapted growth and activity for hydrolysis of o-nitrophenyl-β-D-galactopyranoside (ONPG) and lactose in cell free extracts. Strain KNOUC403 showing negative activity in β-hemolysis was selected and identified. The strain was gram-positive bacilli, non-motile, catalase-positive and aerobic. Optimum growth was done at 20°C and pH 6.5~6.8. Anteiso-C15:0 (68.14%) was predominant in the fatty acid composition of cell. The physiological and biochemical properties, cellular fatty acid composition and sequence of 16S rDNA, suggest that strain KNOUC403 indicate a taxonomic affiliation to Arthrobacter psychrolactophilus. The optimal conditions for ONPG hydrolysis of cell free extracts from the strain were 15°C and pH 6.0, and the enzyme was stable at 4°C for 42 h. Zymogram assay of cell free extract from the strain in nondenaturing polyacrylamide gel showed a distinct band of X-gal hydrolysis.


Key words: Psychrophilic bacteria, Arthrobacter psychrolactophilus, cold-active lactose hydrolyzing enzyme, Mt. Himalaya.