Enzymatic Degradation of Polycaprolactone by Cutinase-Producing Bacteria Isolated from Plastic-Contaminated Environments

The escalating accumulation of synthetic polymer waste underscores the urgent need for sustainable biodegradation strategies. Among microbial enzymes, cutinases have recently gained prominence for their ability to hydrolyze aliphatic polyesters such as polycaprolactone (PCL). This study reports the isolation and characterization of PCL-degrading bacteria from plastic-contaminated sites in the Bursa region of Turkey, expanding the known ecological distribution of cutinase activity microorganisms. A total of 82 bacterial isolates were obtained, of which 14 exhibited hydrolytic activity on Tween 20, Tween 80, and PCL-containing media, indicative of extracellular esterase/cutinase activity. Three isolates—Peribacillus sp. M.2.2, Peribacillus sp. K.2.2, and Stutzerimonas sp. G.K.5.1—showed the most prominent PCL degradation zones and were selected for further analysis based on 16 S rRNA gene sequencing. Among these isolates, Stutzerimonas sp. G.K.5.1 achieved a degradation efficiency of 10.75% in PCL films within 10 days under mesophilic conditions, suggesting measurable enzymatic depolymerization. Optimal parameters for growth, enzyme activity, and total protein content were systematically determined, with tomato-derived cutin identified as an effective natural inducer of cutinase activity. These findings indicate that Stutzerimonas sp. G.K.5.1 and Peribacillus species possess extracellular cutinases that contribute to PCL depolymerization. The study provides additional insight into bacterial cutinase-mediated polyester degradation and supports the potential use of naturally occurring microorganisms in future enzyme-based plastic bioremediation approaches.