Synthesis and optimization of nano-sized bacterial-based violacein pigment using response surface methodology

Abstract

Violacein from Chromobacterium violaceum has raised the enthusiasm of researchers in conducting comprehensive studies on these pigments due to their diverse biological activities including antibacterial and antioxidant properties. However, a limitation related with the solubility of the violacein pigment, by which it is commonly dissolved in toxic solvents such as dimethyl sulfoxide and methanol instead of being soluble in biological fluids and water. Hence, this study provides a method to synthesis the violacein pigment in nanoscale through an encapsulation technique using chitosan-tripolyphosphate (Cs-TPP) nanoparticles. The synthesis of nanoparticles in this study involved ionic gelation between chitosan and tripolyphosphate (TPP), in which several parameters were taken into consideration in order to control the size and dispersion stability of the violacein pigment in the suspension. Preparation parameters, including the concentration of chitosan, TPP and pigment as well as the mass ratio of chitosan to TPP, were optimized using Response Surface Methodology (RSM). Minimum particle size of 149.0 nm with zeta potential of +23.40 mV was obtained at the optimal formulations of 2.33 mg/mL of chitosan, 1.5 mg/mL of TPP, and 1 ppm of violacein pigment and at mass ratio of chitosan:TPP of 7:1. This nano-sized violacein pigment is expected to be applied as safe additive, colorant, and therapeutic agents. Meanwhile, RSM in the study could provide the optimal formulations for producing stable nano-sized violacein pigment.