Effect of KNO₃ Concentrations on the Growth and Physiological Characteristics of Rhodella reticulata

The unicellular red alga,Rhodella reticulata,can synthesize some bioactive substances such as phycobiliprotein and exopolysaccharides.In this paper,the growth and physiological of Rh.reticulata under different KNO₃ concentrations were studied.The parameters,such as growth rate,exopolysaccharide,phycocyanin,pigments,nitrate reductase and SOD,were used in the assays.The result showed that Rh.reticulata grew the best under 0.75 g/L nitrate condition compared with nitrogen free medium,the alga also produced the highest activity of nitrate reductase,phycocyanin content（24 mg/L）,and caroteneid（1.42 mg/L）.While at the concentration 7.5 g/L nitrate,Rh.reticulata produced the most content of chlorophyll a（1.91 mg/L）.Higher nitrogen promoted the accumulation of Rh.reticulata exopolysaccharides.We got 1.633 g/L of exopolysaccharides when the concentration of nitrate was 30 g/L.With the increasing of KNO₃ concentration,the activity of SOD enhanced.