Zhang_2018_J.Biotechnol_281_74

A novel method to synthesize poly(sigma-caprolactone) (PCL) through a three-step, lipase-mediated chemo-enzymatic reaction from cyclohexanone using an immobilized lipase from Trichosporon laibacchii (T. laibacchii) CBS5791 was developed. The immobilized preparation with 1280 U. g(-1) used here was obtained by a method of purification and in situ immobilization where the crude intracellular lipase (cell homogenate) was subjected to partial purification by an aqueous two-phase system (ATPS) consisting of 12% (w/w) polyethylene glycol (PEG) 4000 and 13% (w/w) potassium phosphate (K(2)HPO(4)) and then in situ immobilization directly on diatomite from the top PEG-rich phase of ATPS. In this multi-step process, the sigma-caprolactone (sigma-CL) produced by lipase-mediated one-pot two-step chemo-enzymatic oxidation of cyclohexanone was directly subjected to in situ ring-opening polymerization (ROP) started by adding highly hydrophobic solvents. It is necessary to note that sigma-CL synthesis and its subsequent ROP were catalyzed by the same lipase. The impact of various reaction parameters, e.g., solvent, cyclohexanone: hydrogen peroxide molar ratio, hydrogen peroxide forms and reaction temperature were investigated. Toluene was selected as a preferred solvent due to supporting the highest molecular weight (M(n) = 2168) and moderate sigma-CL conversion (65.42%). Through the optimization of reaction conditions, PCL was produced with a M(n) of 2283 at 50 degreesC for 24 h. These results reveal that this lipase-mediated direct ring-opening polymerization of in situ formed sigma-CL is an alternative route to the conventional synthesis of PCL.