Enhanced Colaconema formosanum biomass and phycoerythrin yield after manipulating inorganic carbon, irradiance, and photoperiod

[Display omitted] •Inorganic carbon enhances macroalgae biomass and pigment production.•One g L-1 of mixed carbon provides a pH in a range for optimal algal growth.•Algae adjust allophycocyanin content to adapt to increasing daily light.•Algae adjust the ratios of phycoerythrin and allophycocyanin to adapt to added carbon.•One g L-1 inorganic carbon increased biomass by 60%. Due to an increasing CO2 concentration leading to global warming, the techniques as carbon capture utilization and storage are currently critical issues. This study aimed to investigate a cultivation strategy using optimal inorganic carbon level, irradiance, and photoperiod for producing the highest biomass and photosynthesis pigment contents (chlorophyll and phycobiliprotein) in the macroalga Colaconema formosanum. The results revealed that adding 1 g L-1 carbon increases phycoerythrin ratio by 12.52–13.74% and decreases allophycocyanin by 10.4–9.57%. Optimal conditions can increase algal growth by 60%, providing 5–6 mg g−1 total phycobiliprotein and 650–680 µg g−1 total chlorophyll. The results in this study illustrate the sensitivity of photosynthesis pigment after treatment with carbon, and suggest a hypothesis explaining the mechanism. The results also provide a feasible use of carbon for high-value large-scale production of pigment in the macroalgae industry.