• Santhini S. Nair
• P.D.Anthappan
• Alok R. Singh

Abstract: Eight different bacterial soil isolates were primarily screened for their potential for synthesizing AgNPs extracellularly, based on Nitratase activity. The Culture supernatants of these isolates was successfully used for AgNP synthesis where the need for downstream processing was not required. Synthesized AgNPs were characterized via UV spectrophotometry and TEM, revealing plasmon resonance band in the range of 410- 420 nm, with spherical nanoparticles in the size range of 2 -50 nm respectively. The soil isolates were further screened secondarily based on their antibacterial activity against the test organisms E. coli NCTC 9022 and S. aureus ATCC 6538P and the better performing isolates were selected as A1, GB1, GD1 and B5 which were all identified by VITEK 2BCL to belong to different Bacillus spps. The synthesized AgNPs from these isolates were stable even after storage for 6 months owing to the capping effects derived from the culture supernatant. Amongst all the isolates AgNPs synthesized from CS of A1 showed maximum antibacterial activity and A1 isolate was used for further optimization of biosynthesis. Different parameters like addition of 1N NaOH to CS, Growth culture density, ratio of CS:1mM AgNO3, and microwave induced biosynthesis were optimized and it was found that efficient synthesis of AgNPs using A1 CS could be achieved rapidly within 40 secs. The A1 isolate was identified by 16srRNA sequencing as Bacillus cereus strain BHAVANI with an Accession No. MH598411.1. Thus, this paves the path for rapid synthesis of AgNPs that has the potential for commercial exploitation using an ecofriendly, simple, cheap and highly reproducible method of biosynthesis of AgNPs.

Bacillus spps, Culture supernatant, Extracellular, AgNPs, Rapid Biosynthesis, Optimization

" Extracellular Synthesis of Silver Nanoparticles using Bacillus spps soil isolates.", International Journal of Emerging Technologies and Innovative Research (www.jetir.org), ISSN:2349-5162, Vol.5, Issue 11, page no.605-616, November-2018, Available :http://www.jetir.org/papers/JETIR1811382.pdf

" Extracellular Synthesis of Silver Nanoparticles using Bacillus spps soil isolates.", International Journal of Emerging Technologies and Innovative Research (www.jetir.org | UGC and issn Approved), ISSN:2349-5162, Vol.5, Issue 11, page no. pp605-616, November-2018, Available at : http://www.jetir.org/papers/JETIR1811382.pdf