Degradation of aliphatic and aliphatic-aromatic co-polyesters by depolymerases from Roseateles depolymerans strain TB-87 and analysis of degradation products by LC-MS

The degradation activities of bacterium, Roseateles depolymerans TB-87 and its depolymerases Est-H and Est-L against aliphatic as well as aliphatic-aromatic co-polyesters, were investigated. Strain TB-87 and its enzymes exhibited an ability to degrade aliphatic and aliphatic-aromatic co-polyesters. Monomers produced as a result of degradation of aliphatic polyesters [poly(butylene succinate) (PBS), poly(butylene succinate-co-adipate) (PBSA)] as well as aliphatic-aromatic co-polyester [poly(butylene succinate/terephthalate/isophthalate)-co-(lactate) (PBSTIL) by depolymerases Est-H and Est-L were investigated by liquid chromatography mass-spectrometry (LC-MS). Some common monomers like succinic acid and 1,4-butanediol were detected besides adipic acid and terephthalic/isophthalic acids as degradation products from PBSA and PBSTIL, respectively, whereas lactic acid was not detected. The succinic acid monomer was detected prior to adipic acid as a result of degradation of PBSA. The enzymes depolymerized PBS also into respective monomers. The analysis of PBSTIL degradation products revealed that enzymes easily degraded aliphatic segments as compared to aromatic segments and resulted in production of succinic acid prior to terephthalic and isophthalic acid. On the basis of these results, we speculate that both the enzymes Est-H and Est-L, attacked succinic acid segments (BS) first instead of adipic acid (BA) and terephthalic/isophthalic acid (BT or BI) segments of PBSA and PBSTIL, respectively. It is concluded from the results that R. depolymerans strain TB-87 can depolymerize aliphatic as well as aliphatic-aromatic co-polyesters; therefore, its enzymes can be applied in the process of biochemical monomer recycling.