Development and optimization of a photoautotrophic phycoerythrin production process

Abstract

Phycoerythrin is a pink pigment produced by photosynthetic microorganisms which has potential to be used as a sustainable colorant in the food, cosmetics and textile industries. In order for this to happen it is necessary to identify suitable strains for large-scale production and develop and optimize production processes. Relatively few species of red algae have been evaluated for their biotechnological potential and to address this gap this work examined five different species of red algae and three cyanobacteria to identify the most suitable candidates for phycoerythrin production. Results from initial screening experiments found a wide range of specific phycoerythrin contents (0.75–28 mg g−1). The four most promising species (<i>Porphyridium purpureum, Rhodella violacea, Timspurckia oligopyrenoides and Flintiella sanguinaria</i>) were grown in 3-L photobioreactors; of the species examined it was found that <i>P. purpureum</i> and <i>R. violacea</i> had the highest growth rate (approximately 0.6 day^−1). As part of the scale-up process it was found that ensuring sufficient nitrate was available in the medium was key in maintaining a high specific phycoerythrin content, with maximum values being 170 ± 34 mg g^−1 for P. purpureum and 120 ± 60 mg g^−1 for <i>R. violacea</i>. Increasing the applied light intensity led to increases in the cell density (to a maximum of 3.46 ± 0.36 g L^−1 for <i>P. purpureum</i>), while the specific phycoerythrin content was generally constant. Applying these insights led to a final volumetric phycoerythrin concentration of 360 ± 37 mg L^−1 for <i>P. purpureum</i> this being a 50-fold improvement over the original values. Results from this work provide valuable data about the growth and phycoerythrin productivity of diverse species of red algae as well as providing valuable insights into how the phycoerythrin production can be optimized.