Pilot-scale production of selenium-enriched Nostoc sphaeroides colonies and polysaccharides using two-phase cultivation strategy

• Published in: Bioresource technology 2025-02, Vol.417, p.131851, Article 131851
• Main Authors: Hu, Jingjing, Liu, Peihua, Wang, Qiangqiang, Nie, Xuyuan, Tan, Jianhua, Shu, Junchao, Mai, Junjian, Cao, Yi, Zou, Yongdong, Huang, Zebo
• Format: Article
• Language: English
• Subjects: biobased products; Biomass; biomass production; Bioselenization; Cell factory; Culture Media; Cyanobacteria; enrichment culture; hardness; Microalgae; Nitrogen; nitrogen-fixing cyanobacteria; Nostoc; Nostoc - growth & development; Nostoc - metabolism; photosynthesis; Pilot Projects; polysaccharides; Polysaccharides - metabolism; selenium; Selenium - metabolism; technology
• ISSN: 0960-8524; 1873-2976; 1873-2976
• DOI: 10.1016/j.biortech.2024.131851

[Display omitted] •Two-phase cultivation produces high-quality selenium Nostoc sphaeroides products.•Separating biomass growth from selenium enrichment avoids negative selenium impacts.•Nostoc bioselenization occurs in phosphate-reduced nitrogen-containing BG-11 medium.•Selenium-enriched polysaccharides show properties akin to non-enriched counterparts. Nostoc sphaeroides, originally discovered in selenium-rich fields, is a photosynthetic, nitrogen-fixing cyanobacterium that forms edible spherical macrocolonies. However, prolonged selenium supplementation negatively impacts colony quality in culture. To address this, a two-phase cultivation strategy was developed to spatiotemporally separate biomass accumulation from selenium enrichment, resulting in high-quality selenium-enriched N. sphaeroides colonies. The first phase focused on colony growth in nitrogen-free BG-110 medium, while the second phase emphasized selenium enrichment in selenium-supplemented, phosphorus-reduced, and nitrogen-containing BG-11 medium (“selenium enrichment medium”). Scale-up to 300 L confirmed the robustness of this process, achieving desired colony hardness of ∼3 newtons, selenium content of ∼350 μg/g, and yield of ∼0.5 g/L (dry weight). Additionally, polysaccharides containing ∼110 μg/g selenium were isolated from the colonies, exhibiting biochemical properties similar to selenium-free polysaccharides from control colonies. These results provide valuable insight into the potential of N. sphaeroides as a cell factory chassis for producing selenium bioproducts.