Nitrate and phosphate uptake dynamics in two halotolerant strains of Chlorella vulgaris is differentially influenced by carbon, nitrogen and phosphorus supply

12 pages, 10 figures, 6 tables.-- Data availability: Data will be made available on request

Microalgae are attractive for the development of environmentally sustainable processes with the option for carbon fixation, given the photosynthetic capacity of these microorganisms. Nitrogen and phosphorus are key nutrients for microalgal growth as well as carbon fixation and product formations. These are also important nutrients in agriculture, the sustainable supply of which is a challenge. They are often lost in waste streams but can be effectively recovered using microalgae and made available for agriculture. In this investigation, we systematically examined the nitrate and phosphate uptake response of two halotolerant strains of Chlorella vulgaris exposed to four carbon and three nitrogen and phosphorus supply regimes to develop an understanding of the relationship between uptake and supply in two microalgae strains from a similar habitat. Markedly differential response to changes in carbon and nutrient supply regimes were noted between the supply regimes and the strains. Changes in carbon supply was found to significantly influence nitrogen and phosphorus uptake in the two strains. Kinetics of nutrient depletion and carbon fixation were observed to be dynamic and non-linear for both the strains, under high carbon and nutrient supply regimes. This investigation provides for the first time a clear evidence base for the role of supply regimes in the management of nutrient uptake in microalgae, including the relationship between the two, and the significance of carbon supply in nitrogen and phosphorus uptake by microalgae. This will enable development of sustainable processes and predictable strategies involving microalgae towards net-zero solutions, as well as nitrogen and phosphorus recovery from waste streams

This work was conducted as part of the SuBB project, supported by the Department of Biotechnology (DBT), Govt. of India (BT/IN/Indo-UK/SuBB/28/LU/2013) and the UKRI Biotechnology and Biological Sciences Research Council (UKRI BBSRC) (BB/K020633/1). This project has also received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement No 661063 to M.S.-N, and the Ministry of Education Malaysia and Universiti Malaysia Perlis (UniMAP) for SLTPA scholarship to FS. S.V. also acknowledges financial support from UKRI EPSRC (EP/E036252/1) to Sheffield. The authors also thank Department of Biotechnology Govt of India for sponsoring the NRMC – Marine repository (BT/PR29901/PBD/26/694/2018) and Mission Innovation #5 programme (BT/ PR31336/PBD/26/726/2019) in connection to the proposed study

With the institutional support of the ‘Severo Ochoa Centre of Excellence’ accreditation (CEX2019-000928-S)

Peer reviewed