Scientific and technological challenges of recombinant egg protein production.

Eggs are among the most widely consumed and versatile animal-derived foods and are valued for their exceptional nutritional and functional properties. However, conventional egg production is associated with significant environmental, ethical, and health concerns, increasing the global consumer demand for sustainable animal protein. To address these challenges, recombinant egg protein production through precision fermentation has emerged as a promising alternative. Yet, this alternative production path is still in its infancy, and current efforts in research have not yet led to a widespread adoption of recombinant egg protein. This review provides an overview of the bioprocesses used to produce recombinant egg proteins, highlighting their nutritional, bio-functional, and techno-functional significance. The current state of the art of recombinant egg protein production is presented, with a comparison of different microbial expression hosts in terms of suitability and associated challenges. Only six egg proteins were reported to be expressed at laboratory scale, including ovalbumin (3.7 g/L with Escherichia coli EcN) and ovomucoid (3.2 g/L with Komagataella phaffii). The realization of large-scale production of functional egg proteins remains challenging. These challenges include posttranslational modifications, achieving functionality and cost parity to natural egg proteins, efficient resource bioconversion, and optimizing the bioprocess chain (upstream, bioproduction, and downstream processes). This requires further improvements and research to increase protein titers, space-time yields, and production rates. Nevertheless, recombinant egg protein produced via precision fermentation holds great promise as a functional food ingredient. With further advancements, this approach could contribute to global protein demand, enhance food security, and strengthen food system resilience while providing a more sustainable and ethical alternative to conventional egg production.