Biomass production and pigment content in Arthrospira platensis by adding AuNP(PEG) AND AgNP(PEG) at different growth phases of cultivation cycle

Abstract

The current study aimed to investigate the influence of growth phase on the response of cyanobacterium Arthrospira platensis to the presence of Au and Ag nanoparticles stabilized with polyethylene glycol in the culture medium. Nanoparticles of gold and silver in the applied concentrations altered the accumulation of spirulina biomass, regardless of the physiological growth phase of the culture to which they were added. Changes in the content of pigments in spirulina biomass indicated the presence of harmful effects on cyanobacterial strain. Gold nanoparticles, for instance, significantly reduced the amount of phycobiliproteins in spirulina biomass, and the inhibitory effect was more pronounced when adding nanoparticles in the lag phase of the cultivation cycle. Changes in the content of chlorophyll a and β-carotene occurred by approximately the same principle, while more pronounced effects were observed under the action of gold nanoparticles. Adding nanoparticles in the exponential growth phase showed a dose-dependent inhibitory effect in the case of chlorophyll. The amount of biomass accumulated during the cultivation cycle cannot be considered a sufficient parameter when assessing the possible toxic effects of nanoparticles, and biochemical tests are necessary to detect various deviations from the normal physiological state of spirulina culture.