Phycocyanin (PC) is commercially exploited in various commercial sectors, as novel applications are developed rapidly. However, the state-of-the-art is difficult to define, given the extremely heterogeneous information available. Hence, this study aimed to perform a technological and scientific review on PC production from Spirulina (Arthrospira spp.), based on a bibliometric analysis of patents and research articles deposited from 2015 to 2023. To close the knowledge gap evidenced by the prospection, we optimized the instrumental conditions of microalgae cultivation, i.e., orbital agitation, culture volume, and cultivation time, for the production of PC. We assessed the color parameters and stability of the PC used as an ice cream colorant. The prospection highlighted rather diverse points of view between academia and the industry regarding PC production methods. The optimization showed a substantial impact of cultivation time on PC yield and purity. A purification step via precipitation was note necessary to obtain food-grade PC (purity > 0.7). Optimal experimental conditions were 180 rpm, 250 mL, and 14 days of cultivation. The ice cream colored using PC from the optimized cultivation conditions showed concentration-dependent color variations, without significant color losses for 90 days.

Microalgae have been proposed for the bioremediation of wastewater, as well as for biofertilization and biostimulation of several plant species. This study used Limnospira sp. biomass produced in brewery wastewater to formulate a pelletized biofertilizer. Its efficacy in promoting barley (Hordeum vulgare) growth was then compared with chemical fertilizers and a control group without fertilization on lab- and pilot-scale setups. On a 100-day lab-scale experiment under controlled light (260–280 µmol photons m⁻² s⁻¹) and temperature (20 ± 2 °C), minor differences in plant growth were observed, whereas the elemental composition of the barley plants did not differ, including toxic elements. On a pilot-scale agricultural setup (5 m²) under environmental conditions, barley productivity, protein content, and the percentage of class I grains (diameter ≥ 2.5 mm) significantly increased based on the different dressing techniques used (p < 0.05). Using the microalgae-based biofertilizer for both base and top dressing increased productivity, protein content, and grain size (% class I) by 26.9%, 14.4%, and 8.78%, respectively, compared to using chemical fertilizers (NPK 5:20:20 and urea). These results indicate the great potential of using microalgae biomass from wastewater treatment as biofertilizer for more sustainable agriculture.