Hydrolase-Producing Moderately Halophilic Bacteria from Eshtehard Desert (Iran)
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XPERIMENTAL ARTICLES
Hydrolase-Producing Moderately Halophilic Bacteria from Eshtehard Desert (Iran) K. Fatholahpoor Kamia, M. Ghanea, *, and L. Babaeekhoua aDepartment
of Biology, Islamshahr Branch, Islamic Azad University, Islamshahr, Iran *e-mail: [email protected]
Received April 20, 2020; revised June 28, 2020; accepted July 4, 2020
Abstract—Hypersaline environments harbor a rich microbiota, which produces a wide variety of compounds with potential biotechnological applications. This study was aimed at characterization of halophilic bacteria inhabiting the Eshtehard Desert and screening their hydrolytic activity. Soil samples were taken from Eshtehard Desert, and 32 morphologically distinct colonies were obtained. These isolates were screened for their ability to produce hydrolase enzymes. Of 32 halophilic isolates, most (18 isolates) exhibited lipase activity, followed by protease (12 isolates), and amylolytic activity (11 isolates). Ten potential isolates with higher levels of enzyme activity were characterized using phenotypic and genotypic methods. Phylogenetic analysis based on 16S rRNA gene sequences showed that the isolates belonged to Gammaproteobacteria and Firmicutes. In terms of genera, the isolates belonged to five major genera including Halomonas, Halobacillus, Idiomarina, Oceanobacillus, and Bacillus. The strains belonging to the Firmicutes phylum showed high proteolytic and lipolytic activities. Characterization of the halophilic enzymes showed that in most cases the optimum salt requirement was within the range of 0.5–1 M, optimum temperature between 45–55°C, and their optimum activity was found to occur at pH 8.0 or above. It may be concluded that the diversity of halophilic bacteria in the Eshteharsd Desert can be considered as a potential source of hydrolytic enzymes. To our knowledge, this is the first report on the ability of Idiomarina sp. to produce amylase. The thermostability and alkaliphilic nature of the enzymes obtained in this study make them potentially useful as catalysis under harsh physicochemical conditions encountered in industrial processes. Keywords: Halomonas, Halobacillus, Idiomarina, amylase, lipase DOI: 10.1134/S0026261720060041
Halophilic microorganisms are widespread in such hypersaline environments as saline soils, saline lakes, and salt marshes. Based on their salt (NaCl) requirement, they are classified into three groups: slight, moderate, and extreme halophiles, with the optimal growth rates at 2–5, 5–20, and 20–30% NaCl, respectively (Dworkin, 2006). To survive in high-salt conditions, halophilic microorganisms employ two main mechanisms including (i) salt in and (ii) compatible solute strategies (Tehei et al., 2002; Mevarech et al., 2005; Roberts, 2005). In the latter mechanism, bacteria accumulate organic compounds such as sugars and derivatives, polyols and derivatives, amino acids and derivatives, glycine betaine, ectoine, and hydroxyectoine in response to osmotic stress (Roberts, 2005). These solutes and other compounds such as exopolysaccharides, bacterior
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