The differences in the effects of PVP stabilized silver nanoparticles on the microalga Porphyridium cruentum and the cyanobacterium arthrospira platensis

Abstract

Nanoparticles are increasingly becoming part of microalgal biotechnologies. Certain types of nanoparticles are suggested as stimulators for lipid synthesis in microalgal biofuel production. The variety of responses from microalgal cultures depends on many factors, such as the type of nanoparticles, their size, concentration, origin, the duration of contact with microorganisms, the age of the culture, and the cultivation conditions. Another determining factor in the relationship between microorganisms and the presence of nanoparticles in their growth environment is the type of microorganisms. Eukaryotic organisms, such as microalgae, respond differently to nanoparticles than prokaryotic organisms, such as cyanobacteria. A study was conducted to determine the differences in the effects of PVP-stabilized silver nanoparticles on the microalga Porphyridium cruentum and the cyanobacterium Arthrospira platensis. Silver nanoparticles at concentrations ranging from 0.05 mg/L to 5 mg/L were added to the mineral medium from the first day of the cultivation cycle. The microorganism cultures were cultivated under autotrophic conditions. Biochemical tests were performed on the collected biomass. The cyanobacterium Arthrospira platensis reacted to AgNP-PVP by reducing biomass content and showing an insignificant change in structural compounds. Reduced antioxidant levels evidenced stress in cyanobacterial culture. For Porphyridium cruentum, biomass content increased, while lipid and carbohydrate content decreased. Higher malondialdehyde levels indicated stress in microalgal culture. The variety of responses from microalgae and cyanobacteria cultures to silver nanoparticles supports the idea that diverse mechanisms are involved in maintaining viability, which creates the possibility of remodeling biosynthetic activity depending on the intended purpose.