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Aims: The increasing development of microalgae applications has led to the concentration of new multidisciplinary studies to facilitate commercial cultivation of these organisms due to cost reduction and productivity enhancement. The aim of this study was the growth and quality optimization of Spirulina biomass by changing the dilution of medium and using the aeration cycle.
Materials and Methods: In this experimental study, the effect of concentration of Zarrouk medium (0 to 100% dilution) and aeration cycle on specific growth rate and dry weight, as well as the content of chlorophyll and carotenoids of Spirulina were investigated, using response surface method, central design. A total duration of 16 hours was aerated in any 24-hour period; the interval time between these aerated periods varied between 1 to 8 hours. The data were analyzed by SPSS 16 software, using multiple regression test.
Findings: The highest biomass (0.659mg/ml) was obtained at 80% concentration of culture media and aeration cycle of 2.75 hours and the highest specific growth rate (0.230 daily) was obtained at 60% concentration and aeration cycle of 4.5 hours. The highest aeration cycle (8 hours) resulted in a significant and simultaneous increase in the content of chlorophyll and carotenoids (11.65 and 2.67 mg/g, respectively).
Conclusion: The growth and quality optimization of Spirulina biomass can be accomplished by changing the dilution of the medium and using the aeration cycle.

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Due to considerable carbon removal, high on-site biomass, and lipid production compared to traditional agriculture, and a wide range of final products, recent research has focused on the facile commercialization of Microalgae by increasing productivity and cost-effectiveness. Nowadays, wastewater is used as an inexpensive and easy-accessible culture medium rather than expensive culture medium synthesis on large scale, therefore, simultaneous wastewater treatment and production of biodiesel from microalgae can be considered sustainable, cost-effective, and environmentally friendly approach. In this regard, the present study is aimed to optimize the growth and biomass quality of Chlorella sorokiniana pa.91 microalgae from Sari wastewater culture medium using Magnesium Aminoclay nanomaterial (MgAC). In this study by application of the surface response method - central design, the effect of temperature, light intensity, and nanomaterial concentration was investigated on the parameters including the dry weight of biomass on the seventh day, specific growth rate, chlorophyll, and carotenoids in wastewater after 12 h exposure to visible light. Under 37 μmol photons, m^-2 s^-1 radiation intensity, and in the presence of 0.05 g/L of magnesium aminoclay NM at 20 ^°C, the optimal condition including biomass dry weight, specific growth rate, chlorophyll, and carotenoids increased by 47.13, 30.26, 81.33 and 36.47% respectively compared to the control sample. Also, to make the present study feasible, the test conditions were performed in real wastewater.