ANTIMICROBIAL CHARACTERISTICS OF BIOACTIVE COMPOUNDS BY A THERMOTOLERANT MICROALGA CHLORELLA VULGARIS ISOLATED FROM THERMAL SPRINGS OF TURKEY

Abstract

This study presents bioactive character of 10 thermal microalgae that were isolated from thermal springs (Turkey). Strain A was the most successful microorganism with the maximum antimicrobial activity. Strain A was identified as C. vulgaris according to its 18S rDNA. The effect of nitrogen concentrations (0.5 g/L, 1.0 g/L, and 1.5 g/L) and temperatures (30 °C and 45 °C) on bioactive compounds production by thermotolerant C. vulgaris was studied. The highest antimicrobial effect was found in the biomass when microalga was cultivated in media with 1.0 g/L nitrogen at 30 °C. On the other hand, stress conditions like 45 °C and media with 1.5 g/L nitrogen, microalgae produced more efficient bioactive compounds then at 30 °C in media with 1.5 g/L nitrogen. S. aureus ATCC BAA 976 and S. aureus ATCC 1026 were affected the most by bioactive compounds of C. vulgaris. In addition, chloroform was the most efficient solvent to obtain effective extracts from C. vulgaris. Pigments and polar compounds had important role for higher antimicrobial activity under harsh conditions like 45 °C and media with 1.5 g/L nitrogen. In addition, caffeic acid having bioactive character was firstly shown for C. vulgaris in the current study.