BIOPROSPECTING OF SILVER NANOPARTICLES SYNTHESIZING BACTERIA AND POTENTIAL APPLICATIONS
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Date
2017
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UHF,NAUNI
Abstract
ABSTRACT
The synthesis of nanostructured materials, especially metallic nanoparticles, has accrued utmost interest over the
past decade owing to their unique properties that make them applicable in different fields of science and technology. The
biological method of nanoparticles synthesis is a relatively simple, cheap and environmentally friendly method than the
conventional chemical and physical methods of synthesis. Therefore, isolation and identification of bacteria with ability of
silver nanoparticles synthesis from natural sources is very important in terms of discovering new industrial products.
Keeping in view, a silver mine located at Uchich village of Pulga valley, apple orchards located in Chong village and two
hot water springs located in Manikaran and Vashisth in Kullu district of Himachal Pradesh were selected as a source for
new silver nanoparticles synthesizing bacteria. Therefore, aim of present study was the isolation and characterization of
silver nanoparticles synthesizing bacteria from these sites for biosynthesis of silver nanoparticles followed by applications of
these biosynthesized silver nanoparticles to control various plant pathogens, textile dye degradation, phytotoxicity study and
pesticide degradation. A total of 106 putative silver nanoparticles synthesizing bacterial isolates were obtained from 45
samples collected from different selected sites. Thirty bacterial isolates were selected on the basis of their ability to show
maximum silver nanoparticles synthesizing activity which were characterized morphologically and biochemically. Four
bacterial isolates exhibiting maximum silver nanoparticles synthesizing activity viz., UMAS1, UMBS1.1, UMBP1 and
UMBP2 were selected for further, molecular characterization using 16S rrna gene technology. In silico analysis of 16S rrna
gene sequences led to identification of these bacterial isolates and all the four were found to belong to genus Bacillus and
were identified as Bacillus siralis strain UMAS1, Bacillus siralis strain UMBS1.1, Bacillus algicola strain UMBP1 and
Bacillus tianmuensis strain UMBP2. On the basis of maximum silver nanoparticles synthesizing activity Bacillus siralis
strain UMBS1.1 was selected for in vitro biosynthesis of silver nanoparticles. Maximum silver nanoparticles synthesis was
achieved at 60°C, pH: 8.0 and after 24 hrs of incubation with 3.0mM silver nitrate, 3.0 % tryptone, 3.0 % yeast extract and
2.0% inoculum size. Central Composite Design was used to determine the optimal values of incubation time (A), incubation
temperature (B), pH (C), tryptone concentration (D) and yeast extract concentration (E). The highest activity was obtained
from Run number-22, which consisted of incubation time of 46.0 hrs; incubation temperature of 36.5°C; pH 8.5, 3g/l
tryptone and 3g/l yeast extract leading to 16.06 fold increase in silver nanoparticles activity. In vitro biosynthesis of silver
nanoparticles was carried out using optimum conditions which were characterized using UV-visible spectroscopy, Fourier
transform infrared spectroscopy (FTIR), X-rays diffractions (XRD), Scanning Electron Microscopy (SEM) and Dynamic
Light Scattering (DLS). In the present study, ability of silver nanoparticles and bacterial culture preparation of Bacillus
siralis strain UMBS1.1 was assessed for degradation of eight textile dyes produced significant results. Both Bacillus siralis
strain UMBS1.1 culture preparation as well as silver nanoparticles has significant potential for use in the detoxification of
eight textile dyes and for treating textile waste waters including water recycling. Silver nanoparticles and bacterial culture
preparation were also found to inhibit various fungal and bacterial pathogens under in vitro conditions appreciably. Silver
nanoparticles and Bacillus siralis strain UMBS1.1 culture preparation were also found to degrade chloropyrifos
significantly
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