A Fed‐Batch Synthetic Strategy for a Three‐Step Enzymatic Synthesis of Poly‐ϵ‐caprolactone

• Published in: ChemCatChem
• Main Authors: Scherkus, Christian, Schmidt, Sandy, Bornscheuer, Uwe T., Gröger, Harald, Kara, Selin, Liese, Andreas
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 2016
• Subjects: Antarc*; Antarctica
• Online Access: http://dx.doi.org/10.1002/cctc.201600806; https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1002%2Fcctc.201600806; https://onlinelibrary.wiley.com/doi/full/10.1002/cctc.201600806

Abstract A three‐step enzymatic reaction sequence for the synthesis of poly‐ϵ‐caprolactone (PCL) was designed running in a fed‐batch operation. The first part of the cascade consisted of two oxidation steps starting with alcohol dehydrogenase catalyzed oxidation from cyclohexanol to cyclohexanone and further oxidation to ϵ‐caprolactone (ECL) by means of a Baeyer–Villiger monooxygenase. As a third step, lipase‐catalyzed hydrolysis of the lactone to 6‐hydroxyhexanoic acid (6‐HHA) was designed. With this biocatalytic multistep process reported herein, severe substrate surplus and product inhibition could be circumvented by the fed‐batch operation by adding the cyclohexanol substrate and by in situ product removal of ECL by hydrolysis, respectively. Up to 283 m m product concentration of 6‐HHA was reached in the fed‐batch operated process without loss in productivity within 20 h. After extraction and subsequent polymerization catalyzed by Candida antarctica lipase B, analysis of the unfractionated polymer revealed a bimodal distribution of the polymer population, which reached a mass average molar mass ( M w ) value of approximately 63 000 g mol −1 and a dispersity ( M w / M n ) of 1.1 for the higher molecular weight population, which thus revealed an alternative route to the conventional synthesis of PCL.