Insights into Wastewater Nitrogen Conversion to Protein via Photosynthetic Bacteria
2025
Wei Zhao | Chenghao Wu | Sijia Zheng | Guangming Zhang
The global shortage of protein resources has highlighted microbial processes as a promising solution for protein production. Photosynthetic bacteria (PSB) offer advantages in protein synthesis, yet the mechanisms underlying nitrogen conversion to protein remain insufficiently understood. To clarify these mechanisms, nitrogen metabolism-related genes and networks were analyzed using high-throughput sequencing. Synthetic sugar wastewater served as the initial substrate. The results showed that at a nitrogen concentration of 200 mg/L with a combined NH4-N + NO3-N supply, the nitrogen conversion rate reached 3.3, and protein production peaked at 130.35 mg/(L·:d). Under these conditions, 68.4% of the utilized nitrogen originated from NH4-N, and 31.6% from NO3-N, leading to an increase in pro-N to 12.46 mg. Transcriptome analysis revealed high :expression of nirK, norB, and nosZ, confirming significant denitrification, while the absence of nitrate reductase, GLDH, GDH, and GltS in Rp. palustris corresponded to a lower protein yield of 53.28 mg/(L·:d). Additionally, genes related to nitrogen transport (amtB, nrtABC), ammonium assimilation (glnA, gltB, gltD), and nitrate reduction (nasA, narB) were upregulated, facilitating nitrogen utilization. These findings provide insights into optimizing nitrogen utilization for improved protein synthesis in PSB-based wastewater treatment.
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