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The results of our study strongly suggest that the application of AgNPs as a sporicidal agent could be a new approach in consistently eliminating the hazardous Bacillus spores.

The present work demonstrates the heavy metal resistance and detoxification of Cr(VI) by the probiotic actinobacterial cultures isolated from chicken and goat feces. The actinobacterial isolates were screened for heavy metal resistance by qualitative, semiquantitative assays and Cr(VI) biosorption was determined by analytical techniques such as atomic absorption spectrophotometry and Fourier transform infrared spectrometry (FT-IR). All the tested actinobacterial isolates (n = 20) showed resistance toward K2Cr2O7, NiCl2, ZnCl2, CuSO4 and PbNO3 at 20 mg L−1 concentration. The maximum tolerance concentration values were found to be 200–250 mg L−1 for K2Cr2O7, 100–250 mg L−1 for PbNO3 and <50–250 mg L−1 for NiCl2, ZnCl2 and CuSO4. Among the five tested heavy metals, Cr(VI) was resisted by 95 % of the tested actinobacterial cultures up to 250 mg L−1 concentration; particularly, the isolate LD22 exhibited a high degree of tolerance to all the tested heavy metals. Thus, the isolate was justifiably chosen for Cr(VI) biosorption study and the biosorption efficacy was found maximum at 100 mg L−1 of metal ion concentration (3 g L−1 of biomass dosage and pH 7.0). FT-IR spectrum revealed the chemical interactions between the hydroxyl, amine and carboxyl groups of the biomass and the metal ions. On the basis of phenotypic, physiological, biochemical and molecular characteristics the isolate LD22 was identified as Streptomyces werraensis LD22 (JX524481) which could be used to develop a biosorbent for adsorbing Cr(VI) metal ions.Electronic supplementary materialThe online version of this article (doi:10.1007/s13205-014-0237-6) contains supplementary material, which is available to authorized users.

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Marine actinobacteria have been considered as a potential source of bioactive compounds holding a prominent position as targets in screening programs due to their diversity and their proven ability to produce novel metabolites and other molecules of pharmaceutical importance. In this regard, an attempt was made to study the diversity of actinobacteria and its ability to synthesize silver nanoparticles in Ramanathapuram and Thoothukudi districts of Tamil Nadu. A total of 1143 actinobacteria were isolated, out of which 49 were morphologically distinct based on the spore color, mycelia formation and pigment production. The morphologically distinct isolates were characterized and identified using light microscope as Streptomyces sp. (16), Nocardiopsis sp. (8), Kitasatosporia sp. (7), Actinopolyspora sp. (2), Thermoactinomyces sp. (5), Actinomadura sp. (4) Kibdelosporangium sp. (3), Saccharopolyspora sp. (3) and Thermomonospora sp.(1). The correlation coefficient analysis between the isolates and the physicochemical parameters of the soil revealed positive correlation with nitrogen. Silver nanoparticles production by the green chemistry approach was investigated using the isolated marine actinobacteria which showed that 25 isolates out of 49, synthesized silver nanoparticles.

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