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

Abstract

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.

Bactericidal and Cytotoxic Properties of Silver Nanoparticles

“…Several surfactants can be used to form microemulsion, including cationic cetyltrimethylammonium bromide (CTAB), anionic sodium dodecyl benzene sulfonate (SDBS) and sodium dodecyl sulfate (SDS), and nonionic Triton X-100 [83,84]. Water-in-oil (W/O) microemulsions or reverse micelles are often employed to prepare metallic nanoparticles [85,86,87]. They consist of nanosized water droplets suspended in a continuous oil phase and stabilized by surfactant molecules located at the oil/water interface.…”

“…It is noted that microemulsion process needs large quantities of surfactants and organic solvents, thus increasing the cost of production and polluting the environment. As the surfactants and solvents are mostly toxic [83], recent attention is paid to the use of natural plant extracts as the oil phase and reductant, or microorganisms as biosurfactants to produce AgNPs [86,87].…”

Antimicrobial activity of silver nanoparticles synthesised by using microbial biosurfactant produced by a newly isolated Bacillus vallismortis MDU6 strain

“…are of great importance in terms of their biological and therapeutic use [32]. Even though chemical reducing agents are widely used for the synthesis of metal NPs, but recently green synthesis of NPs with the help of plant extracts are in trends for their environment benign nature [20]. Literature survey shows large number of studies carried out using various plant parts, exudates, starch, animal protein etc.…”

“…Literature survey shows large number of studies carried out using various plant parts, exudates, starch, animal protein etc. [20]. However, the potential application of microbial biosurfactant as a reducing agent for the synthesis of NPs is rarely explored despite their easy to produce nature [20].…”

“…ESI-MS was performed in positive ion mode. Full scan data were obtained by scanning from m/z 150-2000 and fragmentor voltage used was 135.0 V [20].…”