Screening of a thermostable lipase producing bacterium and its enzyme characterization

Thirty-one lipase producing strains were isolated from the soil samples collected in Gansu province by the method of Tween- 80 nutrient agar plate method. One strain Mhy- 1 was selected for the high growth and production of lipase. The strain Mhy- 1 was preliminarily identified as Aeromonas salmonicida by morphological characteristics, physiological and biochemical, and sequence analysis of 16 S rDNA.The optimum temperature and pH for cell growth were 35℃ and pH7.0.The optimum temperature and pH for the lipase production were 30℃ and pH9.0.A lipase was purified from the culture supernatant of the strain Mhy- 1 by means of ammonium sulfate precipitation, column chromatography on DEAE-Sepharose fast flow.The enzyme appeared to be a single peptide of 34 ku on SDS- PAGE. The optimal temperature and pH of for the enzyme reactivity were 45℃ and 8.0respectively.The enzyme was stable at temperatures 30~70℃ and pH7.0~9.0.The purified enzyme could be used to catalyze the production of biodiesel.