Purification and properties of novel aliphatic-aromatic co-polyesters degrading enzymes from newly isolated Roseateles depolymerans strain TB-87

Abstract

A novel aliphatic-aromatic co-polyester degrading bacterium designated as strain TB-87 was isolated from freshwater. Strain TB-87 has been characterized as aliphatic-aromatic co-polyester, poly[(butylene succinate/terephthalate/isophthalate)-co- (lactate)] (PBSTIL)-degrading microorganism since it grows efficiently and forms clear zones on PBSTIL emulsified NB agar plates. The bacterium was identified through 16S rRNA gene sequencing; it was completely matched with Roseateles depolymerans type strain. PBSTIL depolymerase was purified to homogeneity from R. depolymerans strain TB-87, by column chromatography. This strain produced both high and low molecular weight PBSTIL depolymerases with sizes of approximately 31 and 27 kDa, respectively, as determined by SDS-PAGE. The enzymes utilized p-nitrophenyl caproate (C6) as preferred substrate among various p-NP acyl esters, indicating that these are a type of esterases, therefore, designated as Est-H (high) and Est-L (low). The peptide mapping as a result of limited proteolysis, indicated that the enzymes Est-H and Est-L have different pattern of peptide fragments from each other. The enzymes showed activity against PBSTIL, both in emulsified as well as in film form, however, the activity of Est-H was found higher than Est-L. These enzymes were found stable at 20–40 °C and pH 6.0–11.0. Both Est-H and Est-L were capable of degrading other aliphatic as well as aliphatic-aromatic co-polyesters like poly(butylene succinate) (PBS), poly(butylene succinate)-co-(butylene adipate) (PBSA), poly(ε-caprolactone)(PCL), and poly(butylene succinate)-co-(butylene terephthalate) (PBST). It is concluded from the results that enzymes from strain TB-87 can be applied in the process of biochemical monomer recycling.