Antibacterial activity of microalgae Scenedesmus sp and Spirulina platensis extracts grown in the effluent of desalination plants

The aim of this study was investigating the antimicrobial activity of microalgae Sandosmus and Spirulina cultivated in the BG-11 culture medium and the effluent of the desalination facility of Bandar Turkmen unit, Golestan province, in inhibiting the growth of Gram-positive (Staphylococcus aureus) and Gram-negative (Escherichia coli) bacteria. Algae were extracted by water-alcohol method in proportion (500cc of alcohol and 50cc of distilled water) and determination of minimum inhibitory concentration (MIC) was checked by broth micro dilution method (96 house plates), and were compared to their usual environment with the amount of antibacterial activity grown in water. The results of two mentioned bacteria in the presence of different concentrations of aqueous-ethanolic extract within 24 hours showed that in the extract of the genus Sandosmus and Spirulina grown in BG-11 culture medium and 50 and 100% effluent dilutions, there was no antibacterial effect against Escherichia coli and Staphylococcus aureus bacteria during (24 hours). Sandosmus extract grown in BG-11 with 25 and 50 concentrations had higher E. coli bacteria volume than spirulina in the early hours. As the concentration increases, the volume of bacteria decreases in the early hours. Spirulina extract grown in BG-11 showed high resistance to Staphylococcus bacteria in the early hours compared to Sendesmus. Sendesmus extract grown in 50% wastewater compared to Spirulina had the highest amount of E. coli bacteria in the final hours, so it showed a high resistance to E. coli compared to spirulina. Also, in the extract of Sandosmus grown in 50% wastewater at concentrations of 25, 100 and 200 mg/ml in the final hours, the volume of Staphylococcus bacteria was higher than the concentration of 50 mg/ml, and in spirulina there was a constant trend in the final hours. In both extracts grown in 100% wastewater against E. coli bacteria in all concentrations within 4 hours, they showed the highest amount of bacteria. Therefore, in all concentrations of both extracts, they showed an increase in the volume of Staphylococcus bacteria over time (2-4 hours). Therefore, spirulina grown in 100% wastewater had a stable trend in the last hours compared to Sandosmus and showed more resistance to staphylococcus.