Culture study on utilization of phosphite by green microalgae
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Culture study on utilization of phosphite by green microalgae Michiyo Hashizume 1 & Masaki Yoshida 2 & Mikihide Demura 2 & Makoto M. Watanabe 2 Received: 5 November 2019 / Revised and accepted: 21 February 2020 # Springer Nature B.V. 2020
Abstract The continuous decline in phosphorus (P) resources is a serious global issue. Therefore, it is important to develop methods to recover P from waste and wastewater. Most P ores are currently used in the phosphate form in the agriculture industry and in detergents, which results in a large release of phosphates into natural aquatic environments. Much attention has been given to measuring phosphate levels and monitoring water quality, survey, and control of algal phytoplankton dynamics. However, phosphite is oxidized from hypophosphite after plating and discharged as waste, so methods to recycle and reuse phosphite should also be developed. Currently, there is no evidence of phosphite utilization by photosynthetic eukaryotes, including eukaryotic algae. Thus, except for the possible utilization by some bacteria when phosphate is unavailable, the fate of the phosphite that is discharged is mostly unknown. Chlorella vulgaris (NIES-2170), Coccomyxa subellipsoidea (NIES-2166), Scenedesmus obliquus (NIES-2280), and Botryococcus braunii (BOT-22) were cultured in phosphite medium under conditions that prevented phosphate contamination and phosphite oxidation. As a result, the number of C. vulgaris and C. subellipsoidea increased in the phosphite medium, demonstrating the availability of phosphite for the growth of these strains. In particular, the growth of C. vulgaris increased as the phosphite concentration increased. After being cultured for 180 days in photosynthetic conditions, phosphite utilization rates were 32–38%. In contrast, S. obliquus and B. braunii strains did not grow in the phosphite medium. In conclusion, C. subellipsoidea and C. vulgaris utilize phosphite as a P resource, which is a novel finding in photosynthetic eukaryotes. The results of this study may have important implications for the phosphorus redox cycle. Keywords Phosphite utilization . Chlorella vulgaris . Coccomyxa subellipsoidea
Introduction Phosphorus (P) is an essential component for all life on Earth, and its function cannot be compensated by other nutrients. The majority of phosphates in nature exist as calcium phosphate apatite, and their supply solely depends on weathering and the dissolution of this ore, which has a very low solubility. The annual production of phosphate is approximately 40 million t by P2O5 conversion, which comes from roughly 140 million t of phosphate rock (Steen 1998). Approximately 82% of P ores are currently used in fertilizers and another
Michiyo Hashizume and Masaki Yoshida contributed equally to this work. * Makoto M. Watanabe [email protected] 1
Canon Electronics Inc., Saitama, Japan
2
Faculty of Life and Environmental Sciences and Algae Biomass and Energy System R&D Center (ABES), University of Tsukuba, Tsukuba, Japan
5% for livestock feed, wi
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