The demand for milk proteins is on the rise, but sustainability concerns dictate a reduction of animal-based agriculture. Microbial cell factories can be a viable alternative, but their inability to phosphorylate recombinant caseins is a major bottleneck, since phosphorylation is needed for calcium binding and functionality. We propose a solution based on engineered bacterial protein kinases, which results in microbially produced caseins with the correct phosphorylation pattern and functional properties.