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Ph.D.
(Science)
PREPARATION, CHARACTERIZATION AND THERAPEUTIC
APPLICATIONS OF SILVER NANOPARTICLES USING
ACTINOMYCETES
Ph.D. Scholar : Kulshrestha Arun Kumar
Research Supervisor : Dr. Pritiben H. Patel

Regi. No.: 17276481001
Abstract :
This work was conducted to explore the in vitro inhibition of selected human pathogens
by using silver nanoparticles produced by actinomycetes (Streptomyces atacamensis
AK3) and contributes to enhancing knowledge about the effectiveness of silver
nanoparticles for the treatment of human diseases. Twenty bacterial strains were
isolated from the soils of Gujarat. Streptomyces atacamensis AK3, which was found in
soil near the bank of the Tapi river in Surat, Gujarat, showed promising results for
synthesizing silver nanoparticles. The Tapi River, located in Surat, has been found to be
contaminated with heavy metals, which has resulted in the emergence of bacteria that
are resistant to heavy metals. The promising strain of actinomycetes has been examined
and sequenced (GenBank MT626067). Streptomyces atacamensis AK3 strain was
isolated with the actinomycetes isolation media and then subcultured in starch-casein
broth. Following the filtration process, the filtrate was subjected to the addition of silver
nitrate and subsequently placed in a shaking incubator. The intensity of the color change
from yellow to brown was measured with a Shimadzu spectrophotometer-1700. The
peak observed at 420 nm and, furthermore, the turning of the broth culture color to brown
signified the synthesis of AgNPs. The size distribution and zeta potential of silver
nanoparticles were determined with Malvern, and TEM analysis was done to have a
detailed account of the prepared silver nanoparticles’ characteristics. TEM analysis
revealed that AgNPs of size ~20 nm were most abundant in the sample. A Zeta potential
of -28 mV revealed a low degree of aggregation of AgNPs. The diffusion method was
used for the analysis of the efficiencies shown by the synthesized silver nanoparticles
and the antibiotics against various human pathogens. We demonstrated the zones of
inhibition with strain-synthesized silver nanoparticles as 22 mm, 25 mm, 25 mm, 24 mm,
26 mm, 21.6 mm, 23 mm, 20 mm, 21 mm, 24 mm, and 24 mm for Salmonella enterica,
co-agulase negative. Staphylococcus aureus, Klebsiella pneumoniae, Enterococcus
facalis, Bacillus subtilis, Pseudomonas aeruginosa, Bacillus cereus, Listeria
monocytogenes, Staphylococcus epidermidis, Staphylococcus aureus, and E. coli,
respectively. A synergistic study has shown that when AGNPs and antibiotics are used
together to inhibit Campylobacter jejuni and Plesiomonas shigelloides, the results are
better than when antibiotics or nanoparticles are used alone. In conclusion, silver

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