Evaluation of growth, cell size and biomass of Isochrysis aff. galbana (T-ISO) with two LED regimes

Abstract

In contrast to crops, there are fewer studies using LED-based light with green microalgae and none cultivating the microalga Isochrysis aff. galbana (T-ISO) even though of its importance in marine aquaculture.  The objective was to evaluate of white and red LEDs as an alternative source of light to cultivate I. aff. galbana (T-ISO). In order to carry this out white and red LEDs were used with a laboratory built Erlenmeyer-type photobioreactor to determine productivity, cell number and size and biomass composition. Results were compared with standard fluorescent lights of the same light intensity.  The culture system consisted of 3 flasks for applying red LEDs and three for white LEDs and 3 control group flasks illuminated with the normal fluorescent lighting at the similar light intensity of ~60 mM m^–2 s^–1. It was found that the population cell density did not significantly increase with either red LEDs or white LEDs (p > 0.05), if at all. Standard fluorescent lighting (control group) showed significant increases in population cell number (p < 0.05). Through microscopic observation cell size was found to be smaller for white LEDS and even smaller for red LEDs compared to fluorescent lighting. Biochemical composition of proteins, carbohydrates and lipids was similar for all light regimes. The authors suggest that the unexpected non-growth I. aff. galbana (T-ISO), a haptophyte microalga, with white and red LEDs is possibly due to fact that to initiate cell growth this microalgae requires other wavelengths (possibly green) besides red and blue, to allow other pigments, probably fucoxanthin, to capture light.