Cultivation strategies to enhance pigment production from commercially valuable microalgae

This PhD research project aims to investigate and optimize cultivation strategies to enhance pigment production from commercially valuable microalgae at the industrial level. Low pigment productivity, high operational cost, and contamination problems are the most relevant constraints for microalgae production at the industrial scale. The research focused on different microalgae species that had potential in terms of high pigment productivity and tolerance to acidic environments to limit bacterial contamination, such as Galdieria sulphuraria, Chromochloris zofingiensis, Porphyridium marinum, Coccomyxa onubensis, and Nannochloropsis gaditana. Pigments holding strong antioxidant properties were investigated. Particularly, carotenoids such as astaxanthin, lutein and phycobiliprotein such as phycocyanin and phycoerythrin were in the spotlight. These topics were addressed from different perspectives, from laboratory-scale experiments to industrial pilot plants in partnership with TMCI Padovan. It has investigated the effect of several operation parameters, such as light intensity, partial pressure of CO2, and nutrient concentration, along with their interaction to determine optimal cultivation conditions. The research also explored different metabolic modes (photoautotrophic, mixotrophic, and heterotrophic), stress conditions, and various cultivation modes such as two-step, semicontinuous, and continuous to enhance biomass productivity and pigment accumulation. The proposed cultivation strategies successfully implemented bacterial contamination control strategies such as extremophilic species and initial high biomass concentration. Advanced techniques like the Design of Dynamic experiments were applied to model growth and pigment synthesis. The findings contribute to developing a robust cultivation system that enhances pigment production and highlights the complex interaction between environmental parameters in different experimental setups.