Abstract
As global fisheries decline, microbial single-cell protein (SCP) produced from brewery process water has been highlighted as a potential source of protein for sustainable animal feed. However, biotechnological investigation of SCP is difficult because of the natural variation and complexity of microbial ecology in wastewater bioreactors. In this study, we investigate microbial response across a full-scale brewery wastewater treatment plant and a parallel pilot bioreactor modified to produce an SCP product. A pyrosequencing survey of the brewery treatment plant showed that each unit process selected for a unique microbial community. Notably, flow equalization basins were dominated by Prevotella, methanogenesis effluent had the highest levels of diversity, and clarifier wet-well samples were sources of sequences for the candidate bacterial phyla of TM7 and BD1-5. Next, the microbial response of a pilot bioreactor producing SCP was tracked over 1 year, showing that two different production trials produced two different communities originating from the same starting influent. However, SCP production resulted generally in enrichment of several clades of rhizospheric diazotrophs of Alphaproteobacteria and Betaproteobacteria in the bioreactor and even more so in the final product. These diazotrophs are potentially useful as the basis of a SCP product for commercial feed production.
Highlights
Already half of all global fish stocks have been deemed fully exploited (Cressey, 2009), which has led to the collapse of several fisheries and the potential collapse of others over the several decades (Worm et al, 2006)
The microbial response of a pilot bioreactor producing single-cell protein (SCP) was tracked over 1 year, showing that two different production trials produced two different communities originating from the same starting influent
SCP production resulted generally in enrichment of several clades of rhizospheric diazotrophs of Alphaproteobacteria and Betaproteobacteria in the bioreactor and even more so in the final product. These diazotrophs are potentially useful as the basis of a SCP product for commercial feed production
Summary
Already half of all global fish stocks have been deemed fully exploited (Cressey, 2009), which has led to the collapse of several fisheries and the potential collapse of others over the several decades (Worm et al, 2006). Solid byproducts of various forms (spent grains, hops, yeasts, etc.), once a costly landfill waste, have become a livestock feed source. Even after this removal of solids, a large amount of dissolved carbon still remains in the typical brewery wastewater (Hough, 1985). This brewery waste can be aerobically and microbiologically treated in a process-wastewater treatment facility and the carbon-degrading microbiota harvested as dried microbial biomass, called single-cell protein (SCP). Researchers have recognized SCP’s potential as an animal feed for decades, SCP has never fully replaced fish meal at production scale (El-Sayed, 1999). Brewery process water possesses distinct characteristics that make the technology more feasible than most foodprocessing process water types, such as a continuous global year-round production of dissolved carbon process water (Huige, 2006), and an amino acid profile rich in lysine and methionine (two essential amino acids absent from many plant and fungal sources) that is comparable
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