Studying of nanoparticle structures is gaining
momentum because of their great potential in improving
several fields of science such as agriculture. The water
soluble fraction of the extracellular polysaccharides
(EPS)/matrix of the highly EPS producing cyanobacterium
Nostoc commune have been used as a potent reducing and
capping agent for green synthesis of silver nanoparticles.
The size of these nanoparticles with the EPS coat was found
to be in the range of 15–54 nm as analyzed using
transmission electron micrographs. Interestingly, after
washing the EPS coated silver nanoparticles by ethanol, the
size of nanoparticles reduced to less than 15 nm due to the
formation of silver oxide nanoparticles and removal of the
EPS coat. Silver nanoparticles showed antibacterial
properties against Escherichia coli. The minimum inhibitory
concentration (MIC) was 0.012 mg/ml while the minimum
bactericidal concentration (MBC) was 0.016 mg/ml. The
slight difference between the MIC and MBC suggests that
such silver nanoparticles act as a potent bactericidal agent
against E. coli. Presoaking seeds of crop plants (Sorghum
and broad bean) in five-fold MBC of silver nanoparticles
(0.08 mg/ml) did not adversely affect the germination of
Vicia faba L. and Sorghum bicolor plants. Concomitantly,
such fivefold MBC concentration of silver nanoparticles was
powerful sterilizing agent for seeds and grains against
seed/grain-borne microorganisms. The results showed
gradual depletion of the total colony forming units (CFU) in
seeds and grains sterilized with silver nanoparticles than
those sterilized with chlorine. These results suggest that the
water soluble fraction of the extracellular polysaccharides
(EPS)/matrix of Nostoc commune can be used as a potent
reducing and capping agent for green synthesis of silver
nanoparticles and that silver nanoparticles can be used as a
potent surface sterilizi