Intermediate product control in cascade reaction for one‐pot production of ε‐caprolactone by Escherichia coli

Abstract

Abstractε‐Caprolactone is an important non‐toxic compound for polymer synthesis like polycaprolactone which has been widely used in drug delivery and degradable plastics. To meet the demand for a green economy, a bi‐enzymatic cascade, consisting of an alcohol dehydrogenase (ADH) and a cyclohexanone monooxygenase (CHMO), was designed and introduced into Escherichia coli to synthesize ε‐caprolactone from cyclohexanol with a self‐sufficient NADPH‐cofactor regeneration system. To further improve the catalytic efficiency, a carbonyl group‐dependent colorimetric method using inexpensive 2,4‐dinitrophenylhydrazine (DNPH) was developed for assay of cyclohexanone, an intermediate production of cascade reaction. It can be used to screen mutant strains with high catalytic efficiency from high‐throughput library by detecting the absorbance value in microtiter plates (MTP) instead of gas chromatography (GC) analysis. Moreover, an RBS combinatorial library was constructed for balancing the expression of ADH and CHMO from two independent transcriptional units. After the high‐throughput screening based on intermediate product control, an optimal variant with higher substrate tolerance and long‐term stability was obtained from RBS combinatorial library. Through a fed‐batch process, ε‐caprolactone production reached 148.2 mM after 70 h of reaction under the optimized conditions, which was the highest yield achieved to date.

Fast and switchable ring-opening polymerization of biorenewable omega-substituted lactones towards sustainable copolymers with facile control over monomer sequences

“…To ensure a high reactivity difference, unsubstituted lactone ε-caprolactone(ε-CL) was chosen as the comonomer for copolymerization with ε-DL (Table 2). Although ε-CL is usually prepared industrially from petrol, more and more studies are now focused on developing green and efficient methods for the preparation of ε-CL, 58 which makes it potentially sustainable. U2/IMes, which exhibits moderate activity in the homopolymerization of ε-DL, was first selected as the catalyst for copolymerization with ε-CL (Table 2, entry 1).…”