Bacterial degradation kinetics of poly(Ɛ-caprolactone) (PCL) film by Aquabacterium sp. CY2-9 isolated from plastic-contaminated landfill

Despite the identification of numerous bioplastic-degrading bacteria, the inconsistent rate of bioplastic degradation under differing cultivation conditions limits the intercomparison of results on biodegradation kinetics. In this study, we isolated a poly (Ɛ-caprolactone) (PCL)-degrading bacterium...

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Published in:Journal of environmental management 2023-06, Vol.335, p.117493-117493, Article 117493
Main Authors: Yoon, Younggun, Park, Hyojung, An, Sihyun, Ahn, Jae-Hyung, Kim, Bongkyu, Shin, Jaedon, Kim, Ye-eun, Yeon, Jehyeong, Chung, Joon-hui, Kim, Dayeon, Cho, Min
Format: Article
Language:English
Subjects:
Bacteria - metabolism
Biodegradation
Bioplastic
Degradation kinetics
Kinetics
Mechanism
Plastics
Poly-caprolactone
Polyesters - metabolism
Polymers
Spectroscopy, Fourier Transform Infrared
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Summary:Despite the identification of numerous bioplastic-degrading bacteria, the inconsistent rate of bioplastic degradation under differing cultivation conditions limits the intercomparison of results on biodegradation kinetics. In this study, we isolated a poly (Ɛ-caprolactone) (PCL)-degrading bacterium from a plastic-contaminated landfill and determined the principle-based biodegradation kinetics in a confined model system of varying cultivation conditions. Bacterial degradation of PCL films synthesized by different polymer number average molecular weights (Mn) and concentrations (% w/v) was investigated using both solid and liquid media at various temperatures. As a result, the most active gram-negative bacterial strain at ambient temperature (28 °C), designated CY2-9, was identified as Aquabacterium sp. Based on 16 S rRNA gene analysis. A clear zone around the bacterial colony was apparently exhibited during solid cultivation, and the diameter sizes increased with incubation time. During biodegradation processes in the PCL film, the thermal stability declined (determined by TGA; weight changes at critical temperature), whereas the crystalline proportion increased (determined by DSC; phase transition with temperature increment), implying preferential degradation of the amorphous region in the polymer structure. The surface morphologies (determined by SEM; electron optical system) were gradually hydrolyzed, creating destruction patterns as well as alterations in functional groups on film surfaces (determined by FT-IR; infrared spectrum of absorption or emission). In the kinetic study based on the weight loss of the PCL film (4.5 × 104 Da, 1% w/v), ∼1.5 (>±0.1) × 10−1 day−1 was obtained from linear regression for both solid and liquid media cultivation at 28 °C. The biodegradation efficiencies increased proportionally by a factor of 2.6–7.9, depending on the lower polymer number average molecular weight and lower concentration. Overall, our results are useful for measuring and/or predicting the degradation rates of PCL films by microorganisms in natural environments. [Display omitted] •PCL-degrading Aquabacterium CY2-9 was isolated from plastic-contaminated soil.•Biodegradation of PCL film was observed under both solid and liquid cultivation.•Weight of PCL film was achieved approximately
ISSN:0301-4797
1095-8630
DOI:10.1016/j.jenvman.2023.117493