Influence of phosphorus concentration and temperature on growth and phosphorus uptake by the microalga Scenedesmus obliquus

The growth of the freshwater microalga Scenedesmus obliquus has been studied in a mineral medium with P concentrations of between 0 and 372 μM and temperatures of 20, 25, 30 and 35°C. At all the temperatures, growth was inhibited by the P. The inhibition by P was highly dependent on temperature, detected at concentrations on the order of 1 μM at 35°C, 2 μM at 20 and 25°C, and 350 μM at 30°C. The greatest specific growth rate, 0.047 h−1, was registered at 30°C. The specific growth rates were adjusted to a semistructured model of inhibition by the substrate. The inhibition constants, K1 (μM), increased with rising temperatures from 20 to 25 and 30°C, and decreased at higher temperatures. At 35°C, the lowest value was recorded for K1 1.20 μM, and thus the inhibitory effect was the most pronounced. At 30°C, within the interval of P concentrations of 0–300 μM, it was possible for the variation in μ/S0 to be fitted to a semistructured Monod kinetic model of limitation by the substrate. Yield of biomass varied with temperature. The highest yields were reached at 20°C. The specific rates of P consumption increased with S0, tending towards a constant value. The highest values, obtained at 30°C and 35°C, were practically the same, and the lowest were obtained at 20°C.