Improving light distribution and light/dark cycle of 900 L tangential spiral-flow column photobioreactors to promote CO 2 fixation with Arthrospira sp. cells.

The light distribution and light/dark cycle were improved in 900 L tangential spiral-flow column photobioreactors (TSCP) to promote CO ₂ fixation with Arthrospira sp. cells. Solar irradiation model was employed in CFD simulation to investigate light distribution and light/dark cycle in flow field composed of culture medium, CO2 bubbles and Arthrospira sp. cells under actual sunlight irradiation considering geolocation and time. An accurate way to divide light/dark zone based on saturate light intensity and light intensity field was adopted for the first time. When Arthrospira sp. cell concentration increased from 0.1 to 0.9 g/L, light/dark cycle frequency of cells firstly increased from 0.650 Hz to 0.868 Hz and then decreased to 0.117 Hz. Intracellular chlorophyll a content and carotenoids content of Arthrospira sp. cells in TSCP were 6% and 41% higher than those in conventional bubble column photobioreactor. This promoted cellular photosynthesis and stress resistance, which contributed to increase CO ₂ fixation rate of Arthrospira sp. cells by 59%. When CO ₂ aeration rate, CO ₂ volume concentration, and circulating pump power were 0.210 L/min, 15%, and 30 W, chlorophyll a content, helix pitch, and CO ₂ fixation rate of Arthrospira sp. cells all reached peak values of 8.769 mg/L, 78.26 μm and 0.358 g/L/d, respectively.
Competing Interests: Declaration of competing interest We declare that we have no financial and personal relationships with other people or organizations that can inappropriately influence our work, there is no professional or other personal interest of any nature or kind in any product, service and/or company that could be construed as influencing the position presented in, or the review, of the manuscript entitled “Improving light distribution and light/dark cycle of 900 L tangential spiral−flow column photobioreactors to promote CO(2) fixation with Arthrospira sp. cells”.
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