Precision Fermentation for Animal-Free Dairy Proteins: Microbial Chassis, Molecular Fidelity, Downstream Processing, and the Route to Economic and Regulatory Parity

Dairy proteins, the caseins and whey proteins, underpin the texture, nutrition and functionality of the global dairy sector, yet conventional production ranks among the largest contributors to agricultural land use, greenhouse gas emissions and water consumption. This review synthesises the science and industrialization of precision fermentation as a route to bio-identical dairy proteins made in engineered microorganisms. It focuses on secreted bovine milk proteins (β lactoglobulin, the caseins and lactoferrin) and, as the closest functional comparator, egg ovalbumin, drawing on literature published between 1990 and 2026. The production chassis (Komagataella phaffii, Trichoderma reesei and Aspergillus oryzae) are compared, the molecular fidelity of the recombinant proteins is examined with emphasis on glycosylation and casein phosphorylation, and downstream processing is assessed, where host-derived polysaccharides such as mannan turn out to be an under-appreciated purification burden. The assembled evidence shows that published life-cycle assessments put the carbon footprint of fermentation-derived β lactoglobulin (5.5–17.6 t CO₂e per tonne of protein) in the same order of magnitude as extracted dairy protein, not the order-of-magnitude reductions sometimes claimed, because sugar feedstock and electricity, rather than the cow, dominate the burden. Techno-economic models agree on titres of 50 g/L or more and fermenters of 100,000 L as preconditions for commodity price parity. Regulation is moving faster than the underlying science, with US FDA GRAS no questions letters already issued for β-lactoglobulin (2020, 2023), lactoferrin (2025) and egg white proteins (2021, 2023). Nine concrete research priorities follow from the analysis, and the overall conclusion is that economics, not safety, is now the constraint that matters for adoption.