Selection of microalgae suitable for culturing with digestate from methane fermentation

Area of Science:

• Algal biotechnology
• Waste valorization
• Microbiology

Background:

• Microalgae cultivation is crucial for various applications.
• Digestate from methane fermentation represents a potential nutrient source.
• Optimizing microalgal growth using waste streams is environmentally and economically beneficial.

Purpose of the Study:

• To investigate the growth rates of selected microalgae species in digestate.
• To identify microalgae suitable for culturing with methane fermentation digestate.
• To determine optimal digestate concentrations and light conditions for microalgal growth.

Main Methods:

• Culturing Euglena gracilis, Chlorella vulgaris, and Dunaliella tertiolecta in digestate concentrations (5-100%).
• Utilizing Cramer-Myers (CM) solution as a control medium.
• Monitoring cell counts daily and calculating specific growth rates (mu).
• Conducting experiments under continuous illumination at 30°C and PPFDs of 75-150 µmol m⁻² s⁻¹.

Main Results:

• Microalgae exhibited higher maximum specific growth rates (mu) in appropriate digestate concentrations compared to CM medium.
• Optimal growth rates were observed at 10% digestate for E. gracilis (0.047 h⁻¹), 20% for C. vulgaris (0.065 h⁻¹), and 50% for D. tertiolecta (0.052 h⁻¹).
• Dunaliella sp. demonstrated significantly higher mu (2.5 and 1.1 times) than E. gracilis and C. vulgaris, respectively, in 50% digestate.

Conclusions:

• Selected microalgae species can be cultured effectively at high growth rates using diluted methane fermentation digestate.
• Dunaliella sp. is particularly suitable for cultivation in higher digestate concentrations under low light conditions.
• This study supports the use of digestate as a sustainable medium for microalgal biotechnology.