Analyzing biodegradability of low-density polyethylene by microorganisms from dumping site and enhancement of their biodegradation potential | |
| Author | Pornya Khampratueng |
| Call Number | AIT Diss. no.FB-24-01 |
| Subject(s) | Plastics--Biodegradation Plastics--Environmental aspects Microplastics |
| Note | A dissertation submitted in partial fulfillment of the requirements for the degree of doctor of Philosophy in Food Engineering and Bioprocess Technology |
| Publisher | Asian Institute of Technology |
| Abstract | Microplastics increasingly infiltrate environmental systems and the food chain, severely impacting plastic pollution. Low-density polyethylene (LDPE), used in food containers, is a crucial challenge for environmental contamination. This study aimed to identify effective microorganisms for LDPE biodegradation, investigate the pathway, and develop strategies to enhance the efficiency of LDPE biodegradation. The primary screening, 22 bacteria and 4 fungi were isolated. Out of those, AS3 exhibited the highest LDPE percent weight reduction of 3.06 ± 0.52%, followed by strain AS8 showed 2.01 ± 0.20% after 4 weeks of incubation. The identification of AS3 showed 97.31% similarity to Bacillus toyonensis (MG561349.1), and AS8 exhibited 97.85% similarity to Sphingobacterium sp. (KJ411920.1). Bacillus sp. AS3 and Sphingobacterium sp. AS8 activities for LDPE degradation were quantitatively analysed. Bacillus sp. AS3 showed new functional groups formation on the LDPE film including N-O and C-O groups after incubation. The LDPE biodegradation pathway was projected from identifying depolymerized molecules, suggesting the presence of extracellular enzymes that break down LDPE into smaller molecules. Moreover, physicochemical pretreatment of LDPE before biodegradation demonstrated an effective strategy to enhance the LDPE biodegradation. The pretreated LDPE enhanced microbial biodegradability, improved biofilm formation, and significantly reduced the physical weight of LDPE. Bacillus sp. AS3 demonstrated an increasing LDPE weight loss of 5.06 ± 1.6%. However, the bacterial consortia AS3-8 strains (bacteria AS3 and AS8) illustrated the highest reduction weight of 8.01 ± 0.5% after 45 days of incubation. Consortia AS3-8 also exhibited the highest decrease in physical properties of LDPE significantly, with water contact angle (WCA) decreasing to 64.21 ± 3.69° and tensile strength (TS) decreasing to 17.97 ± 0.3 MPa. The esterase activity reached a maximum of 0.106 U/mL. SDS-PAGE analysis revealed proteins similar to known enzymes, such as laccase and esterase. This study addresses critical knowledge gaps in plastic biodegradation, focusing on the degradation of LDPE and enhancing biodegradation efficiency. |
| Year | 2024 |
| Type | Dissertation |
| School | School of Environment, Resources, and Development |
| Department | Department of Food, Agriculture and Natural Resources (Former title: Department of Food Agriculture, and BioResources (DFAB)) |
| Academic Program/FoS | Food Engineering and Bioprocess Technology (FB) |
| Chairperson(s) | Anal, Anil Kumar |
| Examination Committee(s) | Thammarat Koottatep;Loc, Thai Nguyen |
| Scholarship Donor(s) | Royal Thai Government Fellowship;AIT Fellowship |
| Degree | Thesis (Ph.D.) - Asian Institute of Technology, 2024 |