(351e) Continuous Production of Natural Blue Phycocyanin in Pilot-Scale Bioreactor

Natural blue pigment has numerous health benefits over synthetic phthalocyanine pigments. One of the most potential sources of natural blue pigments is the microalgae and cyanobacteria that have high concentrations of phycocyanin protein. Natural phycocyanin produced by cyanobacteria attracted a lot of interest, which boosted market demand because of its brilliant color and antioxidant qualities. One effective way to fulfill the growing demand for phycocyanin while reducing environmental impact is through the scalability of cyanobacterial production in bioreactors. Bioreactors are used to produce food- and pharmaceutical-grade biomass and biomolecules from microorganisms. Photosynthetic microalgae and cyanobacteria are currently cultured in bioreactors, either in batch or semi-continuous modes. Those approaches are less efficient, labor-intensive, and have high downtime and operating costs due to regular sterilization and cleaning in between cycles. To address those challenges, researchers are working on the development of more efficient production techniques. In this study, we have optimized the growth kinetics of the cyanobacteria Synechocystis spp. 6803, aiming for the maximum production of phycocyanin through the design of experiments (DoE). A series of batch and continuous-design experiments have been conducted in small lab-scale bioreactors to optimize light illuminations and types. Significant differences in dry cell weight, dry biomass, and specific growth rates (SGR) at different light illuminations have been observed. The growth rate of the cells highly depends on the initial cell density, the intensity of light, and the type of LED illumination. The maximum biomass and phycocyanin concentration in batch mode was observed in a lower and narrow white LED illumination of 200–300 µmol.m^-2s^-1. Based on those results, a factorial-designed continuous approach has been applied in lab-scale bioreactors. The results of the continuous experiments showed some promising outcomes toward a steady state of growth with continuous nutrient dilution and regular harvest from the late exponential phase. Higher biomass and phycocyanin production were achieved through increasing light illumination from 200 µmol.m^-2s^-1 to 550 µmol.m^-2s^-1 over the exponential phase. Finally, those results were transferred to a 120-liter pilot-scale bioreactor, where the steady state of the growth was maintained with a 0.15 to 0.18 dilution rate and an average of 10 liters per day of wet biomass harvest. Phycocyanin concentration was observed at 30–50 mg/g dry biomass at a 500 µmol.m^-2s^-1 white LED light illumination. This continuous technique has the potential to increase profitability to one-quarter of the current approaches practiced in the industrial phycocyanin production process. However, further research is needed to prolong the steady state and develop the automated bioreactor technology, aiming at the highest possible natural phycocyanin pigment production.