Evaluation of Spirulina sp. growth in photoautotrophic, heterotrophic and mixotrophic cultures

Spirulina sp. was able to grow photoautotrophically (in the light), heterotrophically (on glucose) and mixotrophically (simultaneously in the light and on glucose). The highest specific growth rate was reached in mixotrophic culture (0.055 h−1, above I=30 W m−2, CGl=0.5 g l−1). The specific growth rate of the alga on 2.5 g l−1 glucose was markedly increased with increasing light intensity up to 30 W m−2. In photoautotrophic culture at a light intensity above 50 W m−2 photoinhibition occurred. Unstructured kinetic models to describe microalgal culture system including photoautotrophic, heterotrophic and mixotrophic specific growth rate as a function of light intensity and glucose concentration were proposed. The models demonstrated that the light intensity for autotrophic culture was 30–50 W m−2, glucose concentration for heterotrophic growth was >0.5 g l−1 and for mixotrophic growth of Spirulina sp. in batch culture using 1 l photobioreactor was >30 W m−2 and glucose concentration >0.5 g l−1.