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Low pH rather than high CO2 concentration itself inhibits growth of Arthrospira

Liu, Wen, Wang, Junfeng, Liu, Tianzhong
The Science of the total environment 2019 v.666 pp. 572-580
Arthrospira platensis, carbon dioxide, flue gas, microalgae, pH, photosynthesis, singlet oxygen
Microalga is a promising candidate for bio-mitigation of CO2. It has been longtime recognized that high CO2 concentration would impose stresses on microalga to suppress the growth. However, this concept was challenged in this research by investigating the growth, photosynthesis and anti-oxidant characteristics of Arthrospira platensis under independent effects of CO2 concentrations and pH. Results showed the growth of A. platensis was only inhibited when broth was in acidic pH. Microalgal cells could deal with high CO2 concentration readily if medium pH was maintained in favorite level. Photosynthesis was inhibited swiftly and significantly under acidified condition. The singlet oxygen was produced in low level for alkalic pH treatment, however it burst quickly after low pH stress was imposed. Accordingly, it was proposed that the phenomena of high CO2 intolerance was caused by CO2 induced pH decline rather than high CO2 concentration itself. This finding has significance on large scale application of microalga based CO2 mitigation and flue gas treatment since it proved concentrated CO2 could be directly assimilated without dilution.