2.5. Estimation of the photosynthetic pigments
The photosynthetic pigments i.e. chlorophyll a (Chl a ) and carotenoids (Car), in each culture of Anabaena PCC 7120 was extracted following the methods of Porra et al. (1989) and Goodwin (1954), thereby recording the absorbance spectrophotometrically (Systronics, India) at 665 nm and 450 nm, respectively. The contents of phycobiliproteins i.e. allophycocyanin (APC), phycocyanin (PC) and phycoerythrin (PE) were determined spectrophotometrically by recording the absorbance of the supernatant at 652, 615 and 562 nm, respectively following the method of Bennett and Bogorad (1973). Following equation was used to determine the phycobiliproteins content (μg mg−1 dry weight):
APC = A652 – 0.208 (A615)/5.09
PC = A615 – (0.474 * A652)/ 5.34
PE = A562 * 2.41 (PC) – 0.849 (APC)/9.62