Interactive effects of temperature up-shift and nitrogen sources on growth and biochemical compositions of Arthrospira platensis C1

Nutrient and temperature are the important limiting factors for the cultivation of microalgae including Arthrospira platensis, a well-known commercial cyanobacterium. This study is aimed to investigate the effects of nitrogen sources and high temperature on growth and biochemical compositions of A. platensis C1. Cells were cultured in Zarrouk’s medium containing sodium nitrate (29 mM NaNO₃^--N as a control) or in modified Zarrouk’s medium replacing 29 mM NaNO₃^--N with 29 mM Urea-N or a combination of 14.5 mM Urea-N and 14.5 mM NaNO₃^--N. The responses of cells were determined under an optimum temperature (35 ̊C) and a high-temperature shift (42 ̊C). The results showed that after 96-hr cultivation at 35 ̊C, growths of A. platensis C1 grown in the urea-containing media were not significantly different compared with control. However, biochemical compositions likely depended on nitrogen sources. Using 29 mM Urea-N, cells increased in carbohydrates but decreased in proteins, pigments (chlorophyll a and phycocyanin), and total fatty acid contents compared with control. Whereas biochemical compositions of cells grown in the medium containing combined nitrogen sources were similar to control. In addition, the responses to high temperature of A. platensis C1 on the growth and biochemicals in the urea-containing media showed different patterns compared with the control. Although high temperature reduced the cell growth, cells grown in the urea-containing media had less effect compared with the control after exposure for 24 hr. Furthermore, at high temperature, cells grown in the 29 mM Urea-N showed an increase in proteins and pigments and a decrease in carbohydrates contents but the biochemicals of the cells grown in the combined nitrogen sources were not significantly changed. This finding revealed that nitrogen sources had a role in responses of A. platensis C1 to high temperature.