Microemulsion synthesis of silver nanoparticles using biosurfactant extracted from MKVIT3 strain and comparison of their antimicrobial and cytotoxic activities.

In the present study, an efficient biosurfactant producing bacterial strain MKVIT3 was isolated from an oil logging area in Vellore district of Tamil Nadu, India. Liquid chromatography-mass spectrometry (LC-MS/MS) analysis was performed for the identification of different congeners present in the extracted biosurfactant. The column purified biosurfactant was used to stabilise the formation of silver nanoparticles (NP) using borohydrate reduction in reverse micelles. The silver NP were characterised using UV-vis absorption spectroscopy, Powder-XRD TEM analysis and zeta potential. A comparative study of the antimicrobial activity and cytotoxic efficacy was done for the extracted purified biosurfactant and the silver NP. The LC-MS/MS analysis of the biosurfactant revealed the presence of five rhamnolipid congeners. The synthesised silver NP showed the characteristic absorption peak in UV-vis at 440 nm. Powder-XRD and TEM analysis revealed the average particle size of the NP as 17.89 ± 8.74 nm as well as their cubic structure. Zeta potential value of -30.9 mV suggested that the silver NPs are stable in the suspension. Comparative study of the antimicrobial activity revealed that the silver NP are more potent than the biosurfactant in inhibiting the growth of microbes. Cytotoxic activity revealed that the biosurfactant are more effective than the synthesised silver NP.