Purified thermostable proteins are essential research reagents, yet their production often involves laborious, stepwise optimization and costly chromatographic methods. These barriers have historically limited in-house protein production to well-equipped labs with significant expertise. A systems engineering approach is presented for streamlined, low-cost production and chromatography-free purification of widely used DNA-modifying enzymes, including Taq DNA Polymerase, Fusion High-Fidelity Polymerase, Thermostable DNA Ligase, and Reverse Transcriptase. This platform integrates autoinducible expression, cell-programmed autolysis and DNA/RNA autohydrolysis, and precipitation-based purification optimized through Design of Experiments. The resulting enzymes are > 95 % pure by SDS-PAGE, active in standard workflows, and produced within one hour of hands-on time using basic lab equipment. A single 20  mL culture yields enzyme for hundreds to thousands of reactions. Purification of Taq was also demonstrated entirely within bioreactors, highlighting scalability. This method offers a generalizable framework for low-cost protein production and illustrates the power of systems engineering in reshaping biomanufacturing.