Enzymatic degradation of poly(R,S-3-hydroxybutanoate) to cyclic oligomers under continuous flow

The enzymatic degradation of chemically synthesized poly(R,S-3- hydroxybutanoate) (PHB) to a reactive cyclic oligomer under continuous flow using an enzyme column was studied and directed towards green chemical recycling. It was confirmed that atactic and syndiotactic PHBs were quantitatively transformed into the corresponding cyclic oligomer by passing through a column packed with immobilized lipase from Candida antarctica (Novozym 435) at 40°C using toluene solution. The degradability of the polymer depended on the reaction conditions, such as flow rate and the polymer concentration. A higher flow rate and higher polymer concentration caused incomplete degradation of the polymer. The 40°C-degradation was suitable for both rapid degradation of PHB and enzyme stability. The degradation activity of the enzyme column was maintained for at least two months at 40°C.