Microalgae cultivation using nitrogen containing wastewater without dilution -Improvement of NH3 tolerance by increasing intracellular pH-

2023 Fiscal Year Final Research Report

• Project/Area Number: 21K20452
• Research Category: Grant-in-Aid for Research Activity Start-up
• Allocation Type: Multi-year Fund
• Review Section: 0303:Civil engineering, social systems engineering, safety engineering, disaster prevention engineering, and related fields
• Research Institution: Soka University
• Principal Investigator: Sekine Mutsumi 創価大学, 理工学部, 助教 (60910388)
• Project Period (FY): 2021-08-30 – 2024-03-31
• Keywords: 微細藻類 / 細胞内pH / アンモニウム廃水 / 遊離アンモニア / 阻害

Outline of Final Research Achievements

In microalgae production using nitrogen-containing wastewater, dilution of the wastewater is essential to mitigate microalgae inhibition by NH3, raising the issue of water consumption. Previous study has suggested that microalgae with higher intracellular pH are more tolerant of NH3. Therefore, this study attempted to increase the intracellular pH of microalgae and thereby increase their NH3 tolerance. The results of determining intracellular pH and NH3 tolerance of six microalgae species showed a positive correlation between intracellular pH and NH3 tolerance (EC50) for cyanobacteria, supporting the hypothesis of previous study. For Chlorella, the addition of bicarbonate successfully increased the intracellular pH by 0.64, while, contrary to expectations, NH3 tolerance was lowered.

Free Research Field

微細藻類生産

Academic Significance and Societal Importance of the Research Achievements

藍藻について細胞内pHとNH3耐性（EC50）に正の相関関係が得られ、これまで種によって傾向が異なり特徴付けが困難であったNH3に対する微細藻類の耐性を各種の細胞内pHにより一般化できる可能性が示された。細胞内pHおよびNH3耐性は培養環境によって変動しにくい種固有のパラメータであることが明らかとなった。この知見は、今後、微細藻類の窒素利用特性の調査に貢献する。副次的に得られた成果である2種の微細藻類の高NO2-耐性の発見によって、研究の大目的であったNH4+含有廃水を無希釈で用いた微細藻類生産の道筋をつけることができた。