Abstract
The halophilic bacterial isolates SS1, SS2, SS3, SS5, and SS8 were characterized for production of industrially important enzymes like amylase, protease, lipase, and glutaminase. Halophilic bacterial isolates SS1 and SS3 exhibited salt dependent extracellular amylase and protease activities. Both the halophilic isolates SS1 and SS3 exhibited maximum amylase and protease activities in the presence of 1.5 and 1.0 M NaCl, respectively, with the optimum pH 8 and temperature 40°C. SS2 showed maximum extracellular protease and lipase activities in the presence of 0.75 M NaCl, at optimum pH of 7, and temperature 37°C. The glutaminase activity of SS3 increased with increase in concentration of NaCl up to 2.5 M. The optimum pH and temperature for L-glutaminase activity of SS3 was 8 and 40°C, respectively. The combined hydrolytic activities of these halophilic bacterial isolates can be used for bioconversion of organic materials to useful products.
Highlights
Hydrolases constitute a class of enzymes widely distributed in nature from bacteria to higher eukaryotes
In this study we describe the screening and characterization of the extracellular hydrolytic enzymes produced by halophilic microorganisms isolated from the soil sediment of Lunsu, a salt water body of Himachal Pradesh, India
After flooding with Gram’s iodine, a clear zone was observed around the growth of halophilic isolates SS1 and SS3, which indicated the presence of amylase activity
Summary
Hydrolases constitute a class of enzymes widely distributed in nature from bacteria to higher eukaryotes. Halozymes have identical enzymatic features like their nonhalophilic counterpart but exhibit marked differences in their structural features which make them functional at harsh conditions [1] These include high proportion of acidic amino-acids located predominantly at the protein surface and requirement of high salt concentration for optimum biological functions. The halophilic enzymes are stable in the presence of high salt concentrations due to conglomeration of slightly hydrophobic groups and hydration of the protein surface due to carboxylic groups present in glutamate and aspartate These halozymes have been commercialized in various industries including food, baking, feed, chemical and pharmaceutical, paper and pulp, detergent, leather industries, fish sauce and soy sauce preparations, saline waste water, and oilfield waste treatment [2, 3]. Some archaeal enzymes are of great interest, such as the amylase of Haloarcula sp., function optimally at 4.3 M salt and stable in toluene, benzene, and chloroform [10]
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