Nitrogen Availability and the Nature of Extracellular Organic Matter of Microalgae

Abstract

Microalgae have the ability to assimilate atmospheric carbon dioxide and organic and inorganic pollutants while simultaneously producing a range of useful intracellular metabolites. Harvesting and concentrating microalgal suspensions, which is commonly performed via coagulation, flocculation, or filtration, is complex, owing to the dynamic character of the cells. The availability of nitrogen to the cells plays a crucial role in the synthesis of intracellular products and in the release of extracellular organic matter. These are expected to have an extensive impact on the harvesting/dewatering behavior. In this study, the role of nitrogen availability in the production and release of extracellular matter was investigated by characterizing the extracellular organic matter composition and association with the cells for three commercially relevant microalgae: Nannochloropsis salina, a marine Chlorella sp., and Haematococcus pluvialis. The results showed that nitrogen limitation reduced the amount of extracellular matter on a per cell basis, despite the bulk concentration increasing due to the increase in the total biomass surface area. In particular, the protein content of the extracellular material was found to decrease across all three species upon nitrogen deprivation. However, there was significant variation in the amount and composition of the extracellular organic matter between the microalgae. This study provides new knowledge of the variations of extracellular substances in relation to microalgae species and cultivation conditions. This has important implications for species selection and optimization of microalgae production, harvesting, and dewatering processes.

CO2 Capture and Utilization Editorial

“…They simultaneously assimilate CO 2 and organic and inorganic pollutants and produce a range of useful intracellular metabolites. Baroni et al investigated the role of nitrogen availability in the production and release of extracellular matter in three commercially relevant microalgae . Variations of extracellular substances, in relation to microalgae species and cultivation conditions, were reported, with important implications for species selection and optimization of microalgae production, harvesting, and dewatering processes.…”

Maximizing Energy Content and CO2 Bio-fixation Efficiency of an Indigenous Isolated Microalga Parachlorella kessleri HY-6 Through Nutrient Optimization and Water Recycling During Cultivation

“…The nature of EOM varies with the growth stage and is also affected by nitrogen availability in the media. Under nitrogen-replete conditions, most EOM is composed of protein, while under nitrogen-deplete conditions, adopted for lipid induction, EOM is mainly composed of polysaccharides ( Baroni et al, 2020 ). Growth was severely inhibited during the third cycle, and bacteria were observed.…”

Interactions between polyethylene and polypropylene microplastics and Spirulina sp. microalgae in aquatic systems

“…Their results showed that a decrease in nitrogen is directly proportional to the decrease in total proteins produced. Recently, Baroni et al. (2020) examined extracellular organic matter (EOM), specifically the protein and carbohydrates, in several microalgae with a ratio of nitrogen supply in kultur.…”