Combined effect of light intensity and glucose concentration on Arthrospira platensis growth and photosynthetic response was evaluated using a 3 2 factorial design. This design was carried out with light levels of 50, 100, and 150 µmol photons m −2 s −1 and glucose concentrations of 0.5, 1.5, and 2.5 gL −1 . Results from the response surface methodology were that the highest level of light intensity and glucose concentration improved biomass (1.33 gL −1 ), maximum specific growth rate (0.49 day −1 ), and net photosynthetic rate (139.89 µmol O 2 mg Chl −1 h −1 ). Furthermore, the interaction of both factors showed that at low light, glucose had a low effect on maximum biomass and maximal net photosynthetic rate. However, at the highest light levels, the effect of glucose was more sensitive and the increase of glucose concentration increased the levels of all responses. The rates of the instantaneous relative growth, net photosynthesis, and dark respiration of growth cultures showed two different phases in mixotrophic condition. The first was distinguished by the preponderance of the photoautotrophic mode; the second was based mainly on photoheterotrophy.

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