Evaluation of the phototrophic growth of Haematococcus pluvialis under outdoor lighting conditions inside a bubble column reactor at a laboratory scale

Abstract

Haematococcus pluvialis is a green microalga of commercial and industrial interest due to its ability to accumulate high amounts of astaxanthin. In the present work, the photoautotrophic growth of a local strain of H. pluvialis is evaluated and analysed under illuminating conditions corresponding to a bubble column reactor located in Santa Fe, Argentina. Lighting conditions were reproduced using a previously developed methodology published by our research group, based on solid and rigorous radiation transfer modelling between surfaces. The latter implies using a commercial reactor with a custom-designed LED module attached to deliver the same amount of PAR radiant energy per time and volume unit (volumetric radiant flux, [μmol s−1 L−1]). To this end, typical winter, summer and autumn days were chosen because they differ in the photoperiod, the amount of daily light reaching the reactor, and the hourly values of volumetric radiant flow. In the cultivation experiments, the reactor was operated in batch mode, inoculated with aplanospore cells, and the composition and pH of the medium were allowed to evolve freely. Our data is in agreement with the notion that the lighting profile significantly affects biomass productivity and total carotenoids content. Consistently, life cycle duration and the amount of biomass and pigments produced have changed as well.