Microbial protein from recovered nitrogen: Nutritional quality, safety, and feasibility assessment

In contrast to traditional agriculture, microbial protein (MP) production is highly efficient in nitrogen (N) usage and can be employed to valorize a variety of recovered resources, thereby increasing the overall sustainability of food production. The present study aimed to establish the potential of seven recovered N sources originating from different waste streams for MP production using ethanol and acetate as growth substrates. The evaluation was based on specific growth rate, biomass yield, nutritional quality (i.e. macromolecular composition, amino acid (AA) and lipid profile) and food safety (i.e. concentration of heavy metals, polyaromatic hydrocarbons (PAH), pesticides and antibiotics) of the MP. The majority of the recovered N sources did not affect the kinetics and had a minor impact on the biomass yield, compared to their commercial equivalents. The nutritional content of the biomass was similar to soy Hour and did not show major variations in AA and lipid profile for the different recovered N sources. Considering the heavy metal content, an average-weighing adult should not consume >53-213 g of the microbial biomass produced on recovered N per day due to its high copper content. A substantial amount of PAH were also found in the biomass. A daily consumption of 20 g/person/day would impose 2.0-2.8 times higher dietary exposure than the mean PAH exposure through nutrition in the EU, indicating a potential concern for human health. On the other hand, the biomass was free of antibiotics, and the traces of pesticides found did not raise any major concern for food applications. Based on the results of this work, no evidence was found to restrict the application of microbial biomass produced on recovered nitrogen as food.

Automated summary

Compared to traditional agriculture, microbial protein (MP) production is highly efficient in nitrogen (N) usage and can increase the sustainability of food production by utilizing various recovered N sources. In this study, the potential of seven recovered N sources from different waste streams for MP production was evaluated using ethanol and acetate as growth substrates. The results showed that most of the recovered N sources had minimal impact on MP kinetics and biomass yield compared to their commercial equivalents. The nutritional quality of the MP was similar to soy flour, and there were no major variations in its macromolecular composition, amino acid profile, and lipid profile across different recovered N sources. However, the microbial biomass had high copper content and contained substantial amounts of polyaromatic hydrocarbons (PAH), which could pose potential health concerns. The presence of antibiotics and pesticides in the biomass did not raise major concerns for food applications. Overall, this study found no evidence to restrict the use of microbial biomass produced on recovered nitrogen as food.