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Iron and nitrogen regulate carbon transformation in a methanotroph-microalgae system
Baorui Zhang1, Chen Cai2, Yan Zhou3
1Interdisciplinary Graduate Program, Nanyang Technological University, 61 Nanyang Drive, 637335, Singapore; Nanyang Environment & Water Research Institute, Nanyang Technological University, 1 Cleantech Loop, Singapore 637141, Singapore.
The Science of the Total Environment
|August 17, 2023
Summary
Iron and nitrogen are key nutrients for methanotroph and microalgae (MOB-MG) cocultures. Optimizing iron boosts growth and biogas conversion, while nitrogen impacts growth and protein content, crucial for efficient biogas valorization.
Area of Science:
- Biotechnology and Environmental Science
- Microbial Ecology
- Bioprocess Engineering
Background:
- Methanotroph and microalgae (MOB-MG) cocultures are promising for biogas valorization.
- Understanding nutrient regulation is crucial for optimizing MOB-MG system performance.
- Current knowledge on iron and nitrogen's role in MOB-MG coculture dynamics is limited.
Purpose of the Study:
- To investigate the impact of iron and nitrogen availability on MOB-MG coculture growth, biogas conversion, and biomass composition.
- To determine how nutrient amendments influence the microbial community structure within the MOB-MG system.
- To assess the role of heterotrophic bacteria in the coculture system.
Main Methods:
- Establishment of a high-protein MOB-MG coculture from waste activated sludge using synthetic biogas.
- Controlled amendment of iron and nitrogen levels to evaluate their effects on coculture performance.
- Analysis of specific growth rate, biogas conversion efficiency, and biomass composition (protein, lipid).
- Microbial community analysis using 16S rRNA gene sequencing to identify shifts in MOB and other populations.
Main Results:
- Increased iron availability significantly enhanced specific growth rate (0.18 to 0.62 day⁻¹) and biogas conversion (26.81 to 106.57 mg-C L⁻¹ day⁻¹).
- Nitrogen limitation reduced specific growth rate (0.64 to 0.28 day⁻¹) and protein content (0.51 to 0.31 g/g biomass), while lipid content remained stable.
- Iron and nitrogen amendments shifted MOB populations from Methylococcus/Methylosinus to Methylocystis, with Chlorella consistently dominating microalgae.
- Non-methanotrophic heterotrophs were present but did not compromise system performance, potentially enhancing carbon conversion.
Conclusions:
- Iron and nitrogen are critical regulators of MOB-MG coculture performance, influencing growth, biogas conversion, and biomass quality.
- Optimized nutrient supply, particularly iron, is vital for efficient biogas valorization and biomass production.
- The microbial community structure, including MOB and heterotrophs, plays a role in the overall efficiency of the biogas valorization process.
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