| Resumo: | In the present study, the growth response of Phaeodactylum tricornutum, Nannochloropsis oceanica, and Porphyra dioica cultures with different biomass concentrations to 22 combinations of red (620 nm), green (530 nm), and blue (450 nm) light at 3 different light intensities (200, 500, and 1000 μmol m-2 s-1) was investigated. Photosynthetic oxygen evolution rates as response variable were used to create predictive models with the optimal light conditions to improve growth at different algal growth stages. While P. dioica did not result in positive oxygen evolution rates and thus no model could be established, for P. tricornutum and N. oceanica, predictive models showed statistical significance and were used to develop light regimes, matching the needs of algae cultures at different growth stages (lag, exponential, and late exponential phase). The generated models predicted the least absorbed wavelength (620 nm) as optimal for both algae, suggesting that it penetrated the algal culture deeper and stimulated photosynthesis of more cells than more absorbed wavelengths (e.g., 450 nm) that do not penetrate deeper into the culture. An additional experiment was conducted to validate the obtained light regimes. For this purpose, a novel light system (AlgaeLum) was developed, 3D printed and assembled for testing different light quantities and qualities. Experiments showed no significant differences in growth rate and maximum biomass concentrations compared to the control warm white light for both algae. Less absorbed wavelengths showed to improve photosynthetic efficiency in both microalgal species, especially in highly dense cultures and low light paths, over highly absorbed wavelengths (450 nm). Based on this result, the use of red light (620 nm) LEDs is recommended for N. oceanica and P. tricornutum as it offers an optimal balance between cost-effectiveness in terms of both CAPEX and OPEX) and photosynthetic efficiency. The developed AlgaeLum system can be used in the future to conduct other trials (e.g., continuous cultivation systems), which was not tested in the present study to validate the present results. |
|---|