Abstract
The current work was carried out under a screening program targeted at isolation of bioactive Streptomyces species from soil samples. A total of 54 Streptomyces species were isolated from soil samples, out of which 4 isolates were found to be promising. These isolates were identified as Streptomyces spectabilis, Streptomyces purpurascens, Streptomyces coeruleorubidus and Streptomyces lavendofoliae and their sequences have been deposited in the GenBank. The influence of culture conditions including, incubation time, incubation temperature, initial pH and different carbon and nitrogen sources on growth and bioactive compound formation was investigated. Isolate R1, identified as Streptomyces spectabilis, showed maximum bioactive metabolite production with cellobiose and peptone as the carbon and nitrogen sources, on the 5th day at pH 5 at 30℃. The optimum conditions for production by isolate R3, identified as Streptomyces purpurascens, were observed to be starch and casein as the carbon and nitrogen sources, pH 7, temperature 30℃ and an incubation period of eight days. For isolate R5, identified as Streptomyces coeruleorubidus, maximal production resulted on the sixth day at pH 6 and temperature of 35℃ with mannitol and JBM. Isolate Y8, identified as Streptomyces lavendofoliae, was found to produce high levels of bioactive metabolites in the medium supplemented with starch and peptone on the 10th day at pH 7 and at an incubation temperature of 30℃. The four strains tested here behaved differently, each one requiring specific conditions for maximum growth as well as bioactive metabolite production.
Highlights
Actinomycetes, especially Streptomyces species are a rich source of several useful bioactive natural products with potential applications [1]-[3]
Several cultivation parameters like pH, incubation period and temperature play a major role in the production of bioactive metabolites [13]
The effect of different carbon sources on growth and bioactive metabolite production by the isolates is presented in the Figure 1 and Figure 2
Summary
Actinomycetes, especially Streptomyces species are a rich source of several useful bioactive natural products with potential applications [1]-[3]. They are prolific producers of secondary metabolites, many of which have commercial importance as antibiotics, antiparasitic and antifungal agents, anticancer and immunosuppressive agents [1] [4]-[7]. The ability of Streptomyces cultures to form these bioactive products is not a fixed property but can be greatly increased or completely lost under different conditions of nutrition and cultivation [8]. Several cultivation parameters like pH, incubation period and temperature play a major role in the production of bioactive metabolites [13]
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