This paper describes the development of a biocatalytic process on the multi-dozen gram scale for the synthesis of a precursor to Nylon-9, a specialty polyamide. Such materials are growing in demand, but their corresponding monomers are often difficult to synthesize, giving rise to biocatalytic approaches. Here, we implemented cyclopentadecanone monooxygenase as an Escherichia coli whole-cell biocatalyst in a defined medium, together with a substrate feeding-product removal concept, and an optimized downstream processing (DSP). A previously described hazardous peracid-mediated oxidation was thus replaced with a safe and scalable protocol, using aerial oxygen as oxidant, and water as reaction solvent. The engineered process converted 42g (0.28mol) starting material ketone to the corresponding lactone with an isolated yield of 70% (33g), after highly efficient DSP with 95% recovery of the converted material, translating to a volumetric yield of 8g pure product per liter. (c) 2017 Wiley Periodicals, Inc.