Circular economy approaches in the production of alternative proteins

Proteins are an essential part of human diets as they provide the amino acids required to build structural tissues, enzymes, hormones, antibodies, and several other bioactive molecules. Conventional meat, eggs, and milk are the main sources of protein in Western society, providing all essential amino acids with high digestibility. However, discussions around the sustainability of animal-derived products, besides the ethical concerns related to animal welfare, have boosted the search for alternative proteins. Among the possible alternative protein sources, microbial biomass can be produced from agro-industrial substrates with high efficiency, being possibly integrated to conventional production chains in a circular economy. Another category of alternative proteins, the cultivated meat segment, can also take advantage of circularity strategies in the development of culture media and cell culture inputs of renewable origin and reduced cost. This review presents a description of circular economy approaches in the cultivation of protein-rich microbial biomass, including microalgae, fungi, and bacteria, and describes recent applications of agro-industrial products and by-products in animal cell culture for cultivated meat production.