RESEARCH ARTICLE Biogenic synthesis of silver nanoparticle by using secondary metabolites from Pseudomonas aeruginosa DM1 and its anti-algal effect on Chlorella vulgaris and Chlorella pyrenoidosa Rima Kumari 1 & Manjari Barsainya 1 & Devendra Pratap Singh 1 Received: 23 June 2016 /Accepted: 28 November 2016 /Published online: 13 December 2016 # Springer-Verlag Berlin Heidelberg 2016 Abstract Biogenic synthesis of silver nanoparticles (AgNPs) using extracellular metabolites from the bacterium Pseudomonas aeruginosa DM1 offers an eco-friendly and sustainable way of metal nanoparticle synthesis. The present work highlights the biotransformation of silver nitrate solution into AgNP, mediated by extracellular secondary metabolite pyoverdine, a siderophore produced by P. aeruginosa. The bioreduction of silver ions into AgNPs by using pyoverdine was recorded in terms of Fourier transform infrared spectros- copy (FTIR) analysis and color change in the reaction mixture (AgNO 3 + pyoverdine) from pale yellow to dark brown with absorption maxima at 415 nm. The results of X-ray diffraction (XRD) analysis of AgNPs showed its crystalline face-centered cubic structure. The scanning electron microscopy (SEM) and transmission electron microscopy (TEM) pictures of AgNPs showed spherical morphology of AgNP in the range of 45– 100 nm, with tendency of agglomerations. The energy- dispersive X-ray (EDX) analysis of particles provided strong signal of elemental silver with few minor peaks of other im- purities. The present approach offers a unique in vitro method of metal nanoparticle synthesis by exogenously produced bac- terial secondary metabolites, where direct contact between the toxic metal and biological resource material can be avoided. The biologically synthesized AgNPs are found to have anti- algal effects against two species of Chlorella (Chlorella vulgaris and Chlorella pyenoidosa), as indicated by zone of growth inhibition on algal culture plates. Further results ex- hibit concentration-dependent progressive inhibition of chlo- rophyll content in the algal cells by AgNPs, confirming the algicidal effect of AgNPs. Keywords Pseudomonas aeruginosa . Pyoverdine . Silver nanoparticle synthesis . Chlorella vulgaris . Chlorella pyrenoidosa . Anti-algal effect Introduction Metal nanoparticles are increasingly being used in various fields of the economy, due to its significant application in bioscience and biomedicine as biological tagging agent, bio- marker, antimicrobial agents, pharmaceutical ingredients, pol- lution control, cosmetic industry, drug delivery and safety control, cancer therapy, cryogenic superconducting material, solar cell technology, and biosensors (Salata 2004; Jae and Beom 2009; Shukla and Makwana 2014). It has been estimat- ed that by the year 2015, about one trillion dollars’ worth market of nanotechnology-based products is expected. Among various types of nanoparticles, silver nanoparticle (AgNP or nanosilver) has attracted increasing interest because of its unique properties (e.g., size and shape; optical, electrical, and magnetic properties; chemical stability; and catalytic ac- tion (He et al. 2003; Waghmode et al. 2013; Shah et al. 2015). These characteristics make AgNPs nowadays superior and indispensible. In recent years, AgNPs has also attracted much attention due to its novel application in energy sector where stability and good catalytic perfor- mance of silver-based nanocompounds make it a prom- ising alternative to platinum (Pt) in dye-sensitized solar cell technology (He et al. 2015a,b,c). Responsible editor: Philippe Garrigues * Devendra Pratap Singh dpsingh_lko@yahoo.com 1 Department of Environmental Science, Babasaheb Bhimrao Ambedkar University, Lucknow 226025, India Environ Sci Pollut Res (2017) 24:4645–4654 DOI 10.1007/s11356-016-8170-3