Combined effect of temperature and light intensity on growth and extracellular polymeric substance production by the cyanobacterium Arthrospira platensis

The effects of light intensity and temperature on Arthrospira platensis growth and production of extracellular polymeric substances (EPS) in batch culture were evaluated using a three-level, full-factorial design and response surface methodology. Three levels were tested for each parameter (temperature: 30, 35, 40A degrees C; light intensity: 50, 115, 180 mu mol photons m(-2) s(-1)). Both growth and EPS production are influenced mainly by the temperature factor but the interaction term temperature*light intensity also had a significant effect. In addition, conditions optimising EPS production are different from those optimising growth. The highest growth rate (0.414 A +/- 0.003 day(-1)) was found at the lowest temperature (30A degrees C) and highest light intensity (180 mu mol photons m(-2) s(-1)) tested, no optima were detectable within the given test range. Obviously, optima for growth must be at a temperature lower than 30A degrees C and a light intensity higher than 180 mu mol photons m(-2) s(-1). For EPS production, light intensity had a positive linear effect (optimum obviously higher than 180 mu mol photons m(-2) s(-1)), but for the temperature parameter a maximum effect was detectable at 35A degrees C.