Ɛ-Polycaprolactone degradation by a thermostable lipase isolated from Brevibacillus thermoruber strain 7 

Abstract

An exponentially increasing accumulation of plastic wastes in the environment represents one of the biggest problems of our society that could be resolved by a biodegradation by enough effective degraders and their enzymes. The high catalytic rates of thermophilic enzymes, their thermostability and temperature optimum close to the melting points of some plastics determine thermophiles as a promising way for resolving the problem. In the present work we report on the ability of a thermophilic lipase by Brevibacillus thermoruber strain 7 to degrade Ɛ-polycaprolactone (PCL), the enzyme purification, characterization of its physico-chemical properties, degradation products and its disruptive effect on PCL. The pure enzyme showed a temperature optimum at 55°C and pH 7.5, its half life at 60°C was more than five hours. Its substrate specificity referred the enzyme to the subgroup of lipases in the esterase group. The strong inhibitory effect was observed by detergents, inhibitors and Fe3+, while Ca2+ enhanced its activity. The monomer Ɛ-caprolactone was a main product of the enzyme degradation. The similar elution profiles of the products received after treatment with ultraconcentrate and pure enzyme were observed. The significant changes of PCL appearance comprising the formation of shallower or deeper infolds were observed after week incubation. The high temperature optimum in a large pH area, its thermostability and PCL degradation to its monomer suggest a possible exploration of the enzyme for an effective and environment friendly degradation of PCL wastes.