Abstrait

The Influence of Light Intensity and Photoperiod on the Growth of two Fresh Water Green Algae Tetranephris brasiliensis and Scenedesmus sp Isolated from Estuary

Nadia Yasmine Asfouri, Mohamed Bey Baba Hamed, Sidi-Mohammed El-Amine Abi-Ayad and Sid Ahmed Chawki Lamara

The culture of microalgae requires rigorous control of all growth factors: nutrients, pH, temperature, and light. Among these factors, the light that directly influences photosynthesis mechanism is an important factor in defining optimal conditions for the culture. In this study, the effects of various intensities and its photoperiods on the growth and biochemical composition (carbohydrates, proteins) of two freshwater green algae (Tetranephris brasiliensis and Scenedesmus sp) were studied. Three different light intensities (50, 100 μmol m-2 s-1 and daylight) and three photoperiod cycles (24:0, 18:06 light: dark and natural photoperiod) is launched at a constant temperature of 23°C. Microalgal growth was measured using cell count, specific growth rate and OD in three. The results showed that under the light intensity of 100 μmol m-2 s-1 and photoperiod of 18 hour light: 6 hour dark cycle, Tetranephris brasiliensis, Scenedesmus sp. was found to grow favorably with a maximum cell concentration of 2.88 × 107 cells/mL, which corresponds to the growth rate of 0.253 d-1 for Tetranephris brasiliensis and 2.56 × 107 cells/mL which corresponds to the growth rate of 0.190 d-1 for Scenedesmus sp. These results confirm the real effect of photoperiod on the microalgae growth rate and show a good correlation between the absorbance measurements and cell concentrations.