Production of Chlorella protothecoides biomass, chlorophyll and carotenoids using the dairy industry by-product scotta as a substrate

Microalgae-based systems for the production of high value molecules are an emergent area, representing a great promise for industrial applications. The main challenge, however, is the development of high efficiency strategies for the large-scale production at low costs. The aim of this study was to evaluate the potential of ricotta cheese whey (scotta) to be used as a low-cost alternative substrate to grow the microalga Chlorella protothecoides. Furthermore, a salt and light stress condition was imposed in order to improve the carotenogenesis process. A significant reduction in lactose concentration was observed along the cultivation in the culture mediums containing scotta, indicating that the tested C. protothecoides shifted to mixotrophic growth, using the organic carbon source provided. Mixotrophic cultures presented a higher amount of biomass than the autotrophic one, however, the cellular accumulation of chlorophyll and carotenoids was higher in the latter culture. Despite this, the stress strategy that we applied enhanced carotenogenesis, allowing the cellular accumulation of well quoted carotenoids, namely astaxanthin and lutein/zeaxanthin. The results suggest that scotta has a great potential to be used as a culture medium to grow C. protothecoides. Moreover, through an adequate stress strategy it is possible to control carotenogenesis, allowing the production of high amounts of the desirable high value molecules.