Replicated mesocosm sludge bioreactors for microbial protein production from soybean processing wastewater, 16S rRNA gene amplicons Metagenome Raw sequence reads

Microbial community-based single cell protein (SCP) holds promise as a sustainable source of protein in livestock feed; yet its reproducibility in microbial community composition, and biomass growth when using variable real-world wastewater has not been investigated. Here, the effect of heterogeneity in soybean-processing wastewater on SCP quality was tested using four replicate sequencing batch reactors over 92 d. The dry microbial biomass exhibited a protein content of 39.8 + 5.8% and the yield was 17.74 + 1.68 g dry-weight/g sTKNconsumed. Azospirillum, a nitrogen-fixing bacterium, was the prevalent SCP-producing genus at a relative abundance of 40.6 + 5.1%. Nevertheless, it was undetected in wastewater, where Lactococcus and Weissella dominated. Fish-pathogen-like sequences in the SCP were found only at very low relative abundances (< 0.009%) via metabarcoding, suggesting that the SCP is safe for fish. This study demonstrates the reproducibility of feed-safe SCP production directly from food-processing wastewater for animal diet applications.