Effect of Optimization Factors on the Production of Bacillus subtilis and Escherichia coli Synthesized Silver Nanoparticles

Main Article Content

C. Chi-Nwankwo
J. N. Ogbulie
C. O. Akujobi


The recent discovery of silver nanoparticles and their production from Bacillus subtilis and Escherichia coli have enhanced optimization attempts. Extracellular biosynthesis of silver nanoparticles using the Bacillus subtilis and Escherichia coli cultured supernatants was done according to standard procedures. Optimization of the production of silver nanoparticles was done in a 3 X 3 (three factors) design involving temperature (25, 30 and 35 degrees), pH (6, 7 and 8), and time of incubation (24, 48 and 72 Hours) in a total of 15 non-randomized runs. The result showed a sharp decline in the synthesis of B. subtilis silver nanoparticles (BNP) within the first 40 hours but attained steady optimization between 40 – 60 mins. An exponential increase in BNP synthesis was observed between pH 6 – 7 with a slight decline observed between pH 7 – 8. An increase in temperature from 25-300C resulted in a decrease in the production of BNP while the production of BNP increased over 30-350C. An initial lag in Escherichia coli synthesized silver nanoparticle (ENP) synthesis was observed with temperature variations. ENP synthesis maintained an exponential increase up to pH 7 but decreased with 7>pH≤8. The results showed that the increase in temperature resulted in a gradual decrease in production of ENP producing a negative slope. Therefore, the variations in optimization factors of silver nanoparticles produced from both B. subtilis and E. coli led to improved production.

Silver nanoparticles, E. coli, B. subtilis, optimization.

Article Details

How to Cite
Chi-Nwankwo, C., Ogbulie, J. N., & Akujobi, C. O. (2021). Effect of Optimization Factors on the Production of Bacillus subtilis and Escherichia coli Synthesized Silver Nanoparticles. South Asian Journal of Research in Microbiology, 8(3), 39-47. https://doi.org/10.9734/sajrm/2020/v8i330195
Original Research Article


Saeed S, Iqbal A, Ashraf MA. Bacterial-mediated synthesis of silver nanoparticles and their significant effect against pathogens. Environmental Science and Pollution Research. 2020;27(30):37347-37356.

Aygün A, Gülbağça F, Nas MS, Alma MH, Çalımlı MH, Ustaoglu B, Şen F. Biological synthesis of silver nanoparticles using Rheum ribes and evaluation of their anticarcinogenic and antimicrobial potential: A novel approach in phytonanotechnology. Journal of Pharmaceutical and Biomedical Analysis. 2020;179:113012.

Senapati S. Biosynthesis and immobilization of nanoparticles and their applications. University of pune, India; 2005.

Iravani S. Green synthesis of metal nanoparticles using plants, Green Chem. 2011;13:2638.

Husseiny M, Aziz MAE, Badr Y, Mahmoud MA. Biosynthesis of gold nanoparticles using Pseudomonas aeruginosa. Spectrochimica. Acta. Part A. 2006;67: 1003-1006.

Hasnain MS, Javed MN, Alam MS, Rishishwar P, Rishishwar S, Ali S, Nayak AK, Beg S. Purple heart plant leaves extract-mediated silver nanoparticle synthesis: Optimization by box-behnken design. Mater Sci Eng C. 2019;99:1105–14.

Buchannan RE, Gibbon NE. Bergy’s manual of determinative bacteriology. Williams and wilkins Co.: Baltimore, U.S.A; 1974.

Shahverdi AR, Minaeian S, Shahverdi HR, Jamalifar H, Nohi AA. Rapid synthesis of silver nanoparticles using culture supernatants of Enterobacteriaceae: A novel biological approach. Process Biochem. 2007;42:919-923.

Burt J, Gutierrez-Wing C, Miki-Yoshida M, Jose-Yacaman M. Nobel-metal nanoparticles directly conjugated to globular proteins. Langmuir. 2004:20: 11778-11783.

Pal S, Tak YK, Song JM. Does the antibacterial activity of silver nanoparticles depend on the shape of the nanoparticle? A study of the gram-negative bacterium Escherichia. Appl Environ Microbiol. 2007;73:1712-20.