Biomass production, antioxidant capacity and removal of nitrate and phosphate by marine microalgae Tetraselmis tetrathele cultivated in food wastewater

This study was conducted to investigate the cultivation of Tetraselmis tetrathele in food effluent and the effect of different concentrations of effluent on specific growth rate, biomass, chlorophyll a, chlorophyll b, total carotenoids and comparing them with Conway medium. Meanwhile, in this experiment, the percentage of phosphate and nitrate removal from food effluent by T. tetrathelewas evaluated. For this purpose, T. tetrathele was cultured in two concentrations of 5% and 10% of the effluent of Namino food factory for 9 days. The experiment was performed with full light period and a temperature of 24±2 °C and a light intensity of 35 µmol.m-2.s-1. The highest biomass production (0.27 g/l), chlorophyll a (2.57 mg/l) and specific growth rate (1.62 days) were observed in Conway treatment. The highest amount of total carotenoids was obtained in the treatment with 10% effluent concentration. The antioxidant capacity of microalgae extract showed that in both DPPH and ABTS assays, antioxidant activity were dependent on the concentration of the extract and at a concentration of 2000 μg / ml in the treatment with 10% effluent concentration with 28.4% showed maximum percentage of free radical inhibition of DPPH. ABTS assay showed that at a concentration of 2000 μg / ml extracts of all three treatments had the highest antioxidant capacity (more than 90% of free radical scavenging ABTS) and there weren’t significant differences between the three treatments (p > 0.05). However, at the lower concentrations of the extract, there was a significant difference between varius treatments, so that at a concentration of 600 μg/ml, the antioxidant capacity in Conway and 10% effluent and 5% effluent, were 53.3%, 73.3% and 96.2%, respectively. The results also showed that, T. tetrathele could grow well in these low effluents and remove 74% of phosphate (Treatment 3) and 24% nitrate (Treatment 2) in a short period of 9 days. Therefore, due to the fact that T. tetrathele can significantly remove nitrate and phosphate and produce algal biomass, this species can be well cultivated in food effluents. The results of this study showed that cultivation of T. tetrathele microalgae, in addition to removing contaminants in the effluent, it was possible to produce biomass with suitable growth and valuable composition with high antioxidant capacity, which can be promising. The production sector is a valuable and cost-effective product for use in various industries such as cosmetics and food industries.