Enzymatic Synthesis of Trimethyl-ε-caprolactone: Process Intensification and Demonstration on a 100 L Scale

Optimization and scaling up of the Baeyer–Villiger oxidation of 3,3,5-trimethyl-cyclohexanone to trimethyl-ε-caprolactones (CHLs) were studied to demonstrate this technology on a 100 L pilot plant scale. The reaction was catalyzed by a cyclohexanone monooxygenase from Thermocrispum municipale that utilizes the costly redox cofactor nicotinamide adenine dinucleotide phosphate (reduced form), which was regenerated by a glucose dehydrogenase (GDH). As a first stage, different cyclohexanone monooxygenase formulations were tested: cell-free extract, whole cells, fermentation broth, and sonicated fermentation broth. Using broth resulted in the highest yield (63%) and required the least biocatalyst preparation effort. Two commercial glucose dehydrogenases (GDH-105 and GDH-01) were evaluated, resulting in similar performances. Substrate dosing rates and biocatalyst loadings were optimized. On a 30 mL scale, the best conditions were found when 30mM h–1 dosing rate, 10% (v/v) cyclohexanone monooxygenase broth, and 0.05% (v/v) of glucose dehydrogenase (GDH-01) liquid enzyme formulation were applied. These same conditions (with oxygen instead of air) were applied on a 1 L scale with 92% conversion, achieving a specific activity of 13.3 U gcell wet weight (cww)–1, a space time yield of 3.4 gCHL L–1 h–1, and a biocatalyst yield of 0.83 gCHL gcww–1. A final 100 L demonstration was performed in a pilot plant facility. After 9 h, the reaction reached 85% conversion, 12.8 U gcww–1, a space time yield of 2.7g L–1 h–1, and a biocatalyst yield of 0.60 gCHL gcww–1. The extraction of product resulted in 2.58 kg of isolated final product. The overall isolated CHL yield was 76% (distal lactone 47% and proximal lactone 53%).