Lactobacillus bulgaricus

Naseer, Q. A., Xue, X., Wang, X., Dang, S., Din, S. U. & Jamil, J., 2022, Synthesis of silver nanoparticles using Lactobacillus bulgaricus and assessment of their antibacterial potential, Brazilian Journal of Biology (e 232434) 82, pp. 1-8 : 2

2.1. Lactobacillus bulgaricus : isolation and identification

The Lactobacillus bulgaricus was isolated from raw milk, sample was 10 fold diluted ranging from 10 -1 to10 -10. At the end of dilution, 100 µL of sample was shifted aseptically with the help of micropipette to the Rogasa, and Sharpe (MRS) agar plates by using sterile glass spreader. Afterward, plates were stored at static incubator for 24 hrs at 37 °C. After incubation, the types and number of colonies were counted and examined. The isolated colonies were subcultured in triplicate on freshly prepared MRS plates for purpose to obtain pure culture. The pure strain keep at 4 °C for further analysis. Lactobacillus bulgaricus was identified by mean of biochemical and morphological characteristics.

2.2. Synthesis of AgNPs using Lactobacillus bulgaricus

A loop full pure culture of Lactobacillus bulgaricus was inoculated in MRS broth and incubated overnight at 37 °C. After incubation the biomass was centrifuged at 5000 rpm for 10 minutes and transfers to sterile bottle and preserved at 4 °C for further use in silver nanoparticle synthesis. The synthesis of AgNPs needs precursor, for which silver nitrate (AgNO 3) was used. 10 mL of 1 mMAgNO 3 solution was prepared in 1 mL of cell free supernatant. To obtained reaction the solution was incubated overnight at room temperature. Control solutions were also prepared for comparison, i.e., 10 mL of AgNO 3 and 10 mL of distal water separately. The synthesis of AgNPs was determined by color changes of solution.