Pathways and Mechanisms of Single-Cell Protein Production: Carbon and Nutrient Transformation

This study revealed carbon, nitrogen, and phosphorus biotransformation mechanisms of an enriched purple non-sulfur bacterial culture and investigated its ability to recover nutrients from fermented liquor as single-cell protein. Rhodopseudomonas palustris was the dominant species and demonstrated excellent carbon and nutrient removal performance with continuous accumulation of amino acid, carotenoids, and biomass growth. We discovered that the polyhydroxybutyrate (PHB) content varied according to the availability of an external carbon source rather than nutrients, and it was used as a major carbon and energy source to support biomass growth once the external carbon source was limited. Phosphorus exhibited multiple uptake and release patterns that corresponded to the changes in PHB content. With fermented liquor as feed, a total of 53.4% of organic carbon was removed. The biomass yield was 0.89 g of COD biomass/g of COD. Protein occupied 65% of the biomass cell weight, and 15 types of amino acids were identified.