Isolation, characterization and identification of amylase producing halothermophilic isolates from Howz Soltan Lake, Iran

Abstract

Halophilic bacteria are a group of salt tolerant microorganisms; the production of enzymes by halophilic bacteria, due to their activities in harsh environments, is considered as a major field of investigation. Hence, the present study was conducted for the isolation of halothermophilic bacteria from Howz Soltan salt lake. For this purpose 40 samples were collected from five regions of the Howz Soltan lake. The samples were diluted and cultivated on Molten haloid agar (MH) with different salt concentrations (5-35%). Then the plates were incubated at 35-70°C in aerobic conditions for 7-10 days. The strains were screened for amylase production based on differences in enzyme production. In total 205 strains were grown on media including 5-15% salt concentrations. Of all, 18 strains were hyperhalophilic and could grow on media including 20-35% salt concentrations at 40-70°С. Three (3) isolates were identified as best amylase producers. In addition, the results indicated that maximum enzyme activity was observed at 48 h (18.145 U/ml). The optimal pH, temperature and NaCl concentration for amylase production were 7.0-7.5, 40°C and 15% (2.5 M), respectively. Taxonomic and phylogenetic analysis using 16SrRNA gene sequencing revealed that they belonged to Bacillus licheniformis and Gracilibacillus while the third isolate was closer to β proteobacterium.