Synthesis of stable cadmium sulfide nanoparticles using surfactin produced by Bacillus amyloliquifaciens strain KSU-109

In this study, a surfactin was extracted from a novel surfactant producing bacterial strain Bacillus amyloliquifaciens KSU-109, isolated from rhizosphere of date palm (Phoenix dactylifera), and characterized based on 16Sr RNA and sfp genes using Blastn, Blastx and phylogenetic analyses. The study was performed to obtain a renewable bioresource for surfactin production, and its application in nanotechnology as a non-hazardous and environmentally compatible nanoparticle (NP) stabilizer. The strain KSU-109 produced the surfactin with an average yield of 160 mg/L with strong surfactant activity, reducing the surface tension of the medium from 72 mN/m to 29.3 mN/m. The surfactin preparation was used for synthesizing the cadmium sulfide nanoparticles (CdS-NPs) by mixing 0.005% surfactin with 1 mM Cd(NO3)2 in 1:1 ratio (v/v) and 10 mM Na2S solution at pH 7.2 and ambient temperature, which were stable up to 120 days. The surfactin stabilized CdS-NPs were characterized using XRD, TEM, and spectroscopic techniques. The data revealed a significant role of surfactin as a stabilizer and capping agent, which also causes phase transition to yield the cubic/hexagonal CdS-NPs of average size of 3–4 nm. The results elucidated the significance of biocompatible and biodegradable surfactin as an effective and inexpensive stabilizing agent for developing stable CdS nanoparticles.