3, 4-dihydroxy-L-phenylalanine-derived melanin from Yarrowia lipolytica mediates the synthesis of silver and gold nanostructures

BACKGROUND Nanobiotechnology applies the capabilities of biological systems in generating a variety of nano-sized structures. Plants, algae, fungi and bacteria are some systems mediating such reactions. In fungi, the synthesis of melanin is an important strategy for cell-survival under metal-stressed conditions. Yarrowia lipolytica, the biotechnologically significant yeast also produces melanin that sequesters heavy metal ions. The content of this cell-associated melanin is often low and precursors such as L-tyrosine or 3, 4-dihydroxy-L-phenylalanine (L-DOPA) can enhance its production. The induced melanin has not been exploited for the synthesis of nanostructures. In this investigation, we have employed L-DOPA-melanin for the facile synthesis of silver and gold nanostructures. The former have been used for the development of anti-fungal paints. METHODS Yarrowia lipolytica NCIM 3590 cells were incubated with L-DOPA for 18 h and the resultant dark pigment was subjected to physical and chemical analysis. This biopolymer was used as a reducing and stabilizing agent for the synthesis of silver and gold nanostructures. These nanoparticles were characterized by UV-Visible spectra, X-ray diffraction (XRD) studies, and electron microscopy. Silver nanoparticles were evaluated for anti-fungal activity. RESULTS The pigment isolated from Y. lipolytica was identified as melanin. The induced pigment reduced silver nitrate and chloroauric acid to silver and gold nanostructures, respectively. The silver nanoparticles were smaller in size (7 nm) and displayed excellent anti-fungal properties towards an Aspergillus sp. isolated from a wall surface. An application of these nanoparticles as effective paint-additives has been demonstrated. CONCLUSION The yeast mediated enhanced production of the metal-ion-reducing pigment, melanin. A simple and rapid method for the extracellular synthesis of nanoparticles with paint-additive-application was developed.