Morpho-physiological aspects of Scenedesmus acutus PVUW12 cultivated with a dairy industry waste and after starvation

Among green microalgae, Scenedesmus sp. is known for its potential in wastewater remediation and lipid production, especially under starvation. Moreover, it is often characterised by a mixotrophic metabolism. In this work, we cultivated S. acutus PVUW12 in the presence of a liquid fraction of scotta (LFS), a cheese whey by-product, as source of nutrients. Subsequently, cultures were starved to evaluate lipid production. Cells were analysed to obtain information about growth, nutrient consumption during LFS cultivation, morphology and photosynthetic efficiency. We found that the alga boosted its growth when cultured in presence of LFS. Production of stromatic starch grains, polyphosphate granules, cell wall enlargement and reduction of the photosynthetic efficiency were also induced. Massive lipid accumulation was observed only during starvation, which also induced a strong slowdown of growth, loss of polyphosphate grains and further decrease in photosynthetic efficiency. This study demonstrates that S. acutus PVUW12 can be involved in a two-step cultivation, first by promoting growth using a by-product from cheese industry and second by transferring the microalgae on starvation to induce lipid accumulation for bioenergetics purposes.