A halotolerant alkaliphilic actinomycete, Kut-8, was isolated from saline desert of Kutch, Western India. It has been identified as Streptomyces aburaviensis based on the chemotaxonomic characteristics, including cell wall constituents. Kut-8 is Gram-positive having a spiral sporophore with dark green and fluffy spore mass. It was able to grow with 15%, w/v NaCl with optimum being in the range of 5-10%. It grew optimally at pH 9 with slow growth at neutral pH. The cell wall contained L-diaminopimelic acid and no diagnostic sugars. It produced an antibiotic that selectively inhibited the growth of Grampositive bacteria, with Bacillus subtilis being the most sensitive. Kut-8 secreted the antibiotic optimally during mid-stationary phase (on day 14 of growth in liquid culture). The crude antibiotic metabolites were separated by various solvent systems with hexane-methanol-water giving the best separation. The results of bioautographs revealed the presence of single active compound in the Kut-8 antibiotic filtrate. Partial purification of antibiotic metabolite by charcoal absorption and methanol extraction resulted in enhanced antimicrobial activity by 4.16-fold. The study holds significance as only few salt-tolerant alkaliphilic actinomycetes from saline deserts have been explored and information on their antimicrobial potential is still scarce.
An alkaliphilic and salt-tolerant actinomycete, Streptomyces clavuligerus strain Mit-1, was isolated from Mithapur, the western coast of India. The organism was Gram-positive, having filamentous, long thread like structure. The sporulation started after two days of growth and the optimum level of alkaline protease (130 U/ ml) was produced during the early stationary phase. The strain could grow and produce protease with 0-10% NaCl (w/v), the optimum being 5% NaCl (w/v). Growth and protease production was optimum at pH 9 with substantial decline at neutral pH. Sucrose and gelatin were the best carbon and nitrogen sources respectively, whereas gelatin broth was the preferred medium for protease production. Mit-1 produced substantial protease with various amino acids, when employed as the sole nitrogen sources. Crude substrates, such as molasses, whey and wheat flour had significant effect on enzyme production. The results are quite valuable, as only few actinomycetes, particularly salt-tolerant alkaliphilic ones, have so far been explored for their enzymatic potential and process optimization.
A salt-tolerant alkaliphilic actinomycete, Mit-1 was isolated from Mithapur, coastal region of Gujarat, India. The strain was identified as Streptomyces clavuligerus and based on 16S rRNA gene sequence (EU146061) homology; it was related to Streptomyces sp. (AY641538.1). The organism could grow with up to 15% salt and pH 11, optimally at 5% and pH 9. It was able to tolerate and secrete alkaline protease in the presence of a number of organic solvents including xylene, ethanol, acetone, butanol, benzene and chloroform. Besides, it could also utilize these solvents as the sole source of carbon with significant enzyme production. However, the organism produced spongy cell mass with all solvents and an orange brown soluble pigment was evident with benzene and xylene. Further, the enzyme secretion increased by 50-fold in the presence of butanol. With acetone and ethanol; the enzyme was highly active at 60-80 degrees C and displayed optimum activity at 70 degrees C. The protease was significantly stable and catalyzed the reaction in the presence of xylene, acetone and butanol. However, ethanol and benzene affected the catalysis of the enzyme adversely. Crude enzyme preparation was more stable at 37 degrees C in solvents as compared to partially purified and purified enzymes. The study holds significance as only few salt-tolerant alkaliphilic actinomycetes are explored and information on their enzymatic potential is still scares. To the best of our knowledge this is the first report on organic solvent tolerant protease from salt-tolerant alkaliphilic actinomycetes.
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