Removal and heavy metal uptake in cyanobacteria, Effects of nitrogen starvation on the photosynthetic efficiency, pigment composition and photoinhibition. Growth is performed phototrophycaly in inorganic media at different temperatures and irradiances. Biomass Determination Biomass of microalgae is estimated by tubidimetry at 750 nm, cell counting and dry weight. The activity of each photosystem is estimated using artificial electron donors and acceptors. The photosynthetic capacity and the maximum quantum yield for O 2 evolution are determined using a O 2 electrode at different temperatures.
Light intensity is varied by means of neutral density filters.
The photoinhibitory treatment is performed by submitting cells suspensions under high irradiance at different temperatures, in the presence and absence of protein synthesis or xanthophyll cycle inhibitors. The photosynthetic activity is monitored as oxygen evolution activity or as fluorescence induction. Later on, an actinic light is turned on and pulses of high intensity are superimposed. Chlorophyll fluorescence is detected in a photodiode array at 700 nm and the fluorescence parameters calculated. Isolation of Intact Phycobilisomes Phycobilisomes are isolated in phosphate buffer and purified by ultracentrifugation in discontinuous sucrose gradient.