Production of single-cell proteins from organic matter and residual nitrogen

Abstract The production of microbial proteins (MP) from recovered nitrogen and “waste” organics is an interesting approach that can circumvent the inefficient agriculturally based protein animal feed supply chain. This approach has the potential to significantly lower (waste) water management costs, avoid greenhouse gas emissions, and improve the utilization of resources embedded in wastewater streams. Of particular interest are waste streams originating from food processing and beverage industries, as they are often associated with high carbon, nitrogen, and phosphate concentrations and, moreover, are free of fecal contamination and other pathogens and waterborne viruses. This chapter discusses the key characteristics of four key types of SCPs that can be produced, namely, (i) microalgae, (ii) yeast, (iii) fungi, and (iv) bacteria. Furthermore, for each of these MP production pathways, suitable carbon and energy sources, production processes, and their overall practical and economic feasibility are a means to turn wastewater streams into valuable resources for the production of MP. In summary, microalga-derived products from wastewater still have limited potential due to the low market value and operational constraints to concomitantly produce algal biomass at high product quality and practical relevant scale and process kinetics while meeting discharge limits. Fungal and yeast-derived biomass have better consumer acceptance, although it has yet to be demonstrated in large-scale process plants. bacterium-based MP can be produced from a variety of materials including industrial process waters and can be produced in all types of reactor configurations. Despite its high protein content and good amino acid composition, bacterial biomass has generally as yet low consumer acceptance as human food. The success of microbial protein production from recovered nitrogen and organics from secondary streams goes well beyond engineering and process considerations only. It relies on the production of consistent, safe products that are properly regulated according to up-to-date legislations and careful dialogue with the public at large to gain full consumer acceptance.