Abstract
Halotolerant proteases are known as one of the important groups of enzymes that have been used widely in various industries. However, high production cost of proteases in term of energy used for sterilization and high risk of microbial contamination during fermentation become the obstacles during upstream processing. Moreover, proteases that capable to withstand with harsh conditions of salinity, temperature and pH are required in industry. Therefore, this study presents newly isolated halophilic bacteria producing halotolerant proteases. Halophilic bacteria were isolated from fermented fish sauce. Screening of the bacteria producing halotolerant protease enzymes was carried out by using skim milk salt agar containing 10% NaCl at pH 7 and incubated under aerobic condition at 37oC for 2 days. The selected isolates were identified based on their morphology followed by 16S rDNA gene sequence analysis. 40 colonies of halophiles bacteria were isolated, however, only 20 of them showing proteolytic activity. All of 20 isolates are motile and gram positive bacteria. From 20 isolates, only 6 were chosen for further analysis. B7 showed the highest proteolytic activity compared with others. Results of 16S rDNA gene sequence analysis showed 98% homology to Bacillus amyloliquefaciens subsp. plantarum strain FZB42. Therefore, B7 is identified as Bacillus amyloliquefaciens strain B7.
Highlights
Halophilic bacteria are salt loving organisms that grow in saline environments and can be differentiated based on their requirements for sodium chloride
This study showed the isolation of a strain that is able to grow and tolerate with 10% NaCl concentration which could reduce the risk of microbial contamination
The availability of halophilic bacteria producing halotolerant proteases gave an advantage in industrial processes where high salinity conditions could inhibit mesophilic enzymes
Summary
Halophilic bacteria are salt loving organisms that grow in saline environments and can be differentiated based on their requirements for sodium chloride. The isolation of halophilic bacteria which may be able to produce enzymes which are salt tolerant and tolerate and active at high temperature and pH [14]. Halotolerant proteases were used in the treatment of burns and purulent wounds. It is acts as thrombolytic agent by showing fibrinolytic activity [3]. The aim of this study is to isolate and identify the halophilic bacteria from fermented food that could produce salt stable proteases using 16S rDNA as a molecular marker
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