CHARACTERIZATION OF HALOPHILIC BACTERIUM NB2-1 FROMPLA-RAAND ITS PROTEASE PRODUCTION

Abstract

A halophilic proteolytic bacterium, NB2‐1, isolated from Pla‐ra, fermented fish in Thailand, was identified as Virgibacillus marismortui on the basis of the genetic and phenotypic characteristics. NB2‐1 produced a substantial level of extracellular proteolytic activity, corresponding with the growth and reaching the maximum at the end of the exponential phase (3 days). The optimum conditions required for maximum protease production were 15% (w/v) NaCl, pH at 9 and temperature at 30C. Of the media tested, maximum protease production occurred in a medium containing 15% NaCl, 0.5% yeast extract, 0.1% glutamic acid, 0.2% KCl, 0.3% trisodium citrate, 2% MgSO4·7H2O, 0.0036% FeCl2·4H2O and 0.000036% MnCl2·4H2O. The protease activity was optimally active at pH 10, 50C and 5% (w/v) NaCl when casein was used as a substrate. The activity was strongly inhibited by phenylmethane sulfonyl fluoride. Activity‐stained substrate gel indicated the presence of several proteases with the estimated molecular weights of 17, 19, 24, 29 and 35 kDa in the crude NB2‐1 extracellular protease. The results of the present investigation showed that the strain NB2‐1 could be a potential source of thermoactive alkaline protease production. PRACTICAL APPLICATIONS Halophiles are the most likely source of enzymes that not only are salt‐tolerant but also thermotolerant. They constitute a heterogeneous group of microorganisms including species belonging to different genera. The isolation of halophiles able to produce extracellular enzymes will provide the possibility to have optimal activities at different salt concentrations. Virgibacillus marismortui NB2‐1, a moderately halophilic bacterium isolated from Pla‐ra, produced a substantial level of extracellular proteolytic activity that was active in extreme conditions. Using casein as a substrate, the protease exhibited maximal activity at pH 10, 50C in the presence of 5% (w/v) NaCl. The results of the present investigation showed that the strain NB2‐1 could be a potential source of thermoactive alkaline protease production.

Bioflocculant Production by Virgibacillus sp. Rob Isolated from the Bottom Sediment of Algoa Bay in the Eastern Cape, South Africa

“…The enzyme proteases are found to be produced or secreted most by the genus Virgibacillus and are of particular interest due to their wide applications in laundry detergents, leather processing, protein recovery or solubilization, organic synthesis, meat tenderization, detergents, food industry, photography, and pharmaceuticals [ 23 ]. As an example, protease was produced by a moderately halophilic bacterium isolated from Pla-ra, a fermented fish product in Thailand, and identified as Virgibacillus marismortui NB2-1 [ 24 ]. In another study, an extracellular proteinase produced by Virgibacillus sp.…”

Characterization of Alkaline Phosphatase Producing Bacteria Isolated from Thai Fermented Fish Products

“…Salinivibrio siamensis, Gricilibacillus thailandensis based on 16S rRNA gene sequences and phylogenetic analysis were distributed in fermented fish (pla-ra) and salted fishes (Chamroensaksri et al, 2009Tanasupawat et al, 2007;. V. marismortui strain was characterized as a protease producing moderately halophilic bacterium (Chamroensaksri et al, 2008).…”

Identification of novel halotolerant bacillopeptidase F-like proteinases from a moderately halophilic bacterium, Virgibacillus sp. SK37

“…Like other Gram‐positive bacilli, Virgibacillus showed the ability to produce a great variety of extracellular hydrolytic enzymes. A high production of extracellular proteinases from bacteria in this genus has been reported (Chamroensaksri et al. 2008; Gupta et al.…”

“…Unlike nonhalophiles, moderately and extremely halophilic bacteria growing optimally at between 5 and 25% NaCl are able to produce proteinases exhibiting optimal activity in high ionic strength environments (Kushner showed the ability to produce a great variety of extracellular hydrolytic enzymes. A high production of extracellular proteinases from bacteria in this genus has been reported (Chamroensaksri et al 2008;Gupta et al 2008;Rohban et al 2009;Sinsuwan et al 2007Sinsuwan et al , 2008Sinsuwan et al , 2010. However, information regarding biochemical and molecular characteristics as well as the proteomics of proteinases from Virgibacillus is still very limited.…”