Isolation and Screening of Low-Density Polyethylene (LDPE) Degrading Actinomycetes from Beach and Rice Field Soils

Chan, Joong Kim (2024) Isolation and Screening of Low-Density Polyethylene (LDPE) Degrading Actinomycetes from Beach and Rice Field Soils. Final Year Project (Bachelor), Tunku Abdul Rahman University of Management and Technology.

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Abstract

Low-Density Polyethylene (LDPE) is a type of polyethylene commonly used in our daily life. However, LDPE has made a major contribution to plastic waste, due to its single-use properties, thus leading to plastic pollution. To overcome this problem, the biodegradation of plastic is explored by using microorganisms residing in the biosphere habitat, such as soil. Therefore, this study aims to isolate and determine the population of Actinomycetes from rice fields and beach soils followed by a determination of their plastic degrading capability. Actinomycetes isolates are subjected to macroscopic and microscopic characterization before the first level of screening on Mineral Salt Medium with LDPE powder. Subsequently, Actinomycetes isolates that were able to grow on MSM+LDPE medium were selected for further screening via the weight loss method using LDPE as the sole carbon source for 30 days. FTIR and SEM analyses of LDPE pieces were also performed to determine the LDPE degradation level. The isolation process has yielded Actinomycetes populations of log10 6.03 ± 4.93 CFU/g and log10 5.56 ± 3.51 CFU/g for beach and rice field soils, respectively, showing no significant difference between the soils (p > 0.05). Nine isolates were obtained and subjected to plastic degradation screening. Three isolates (D1, B2, and C2) have shown growing potential during preliminary screening using MSM+LDPE powder and were selected for weight loss screening. Weight loss screening has shown that C2 has a significantly higher LDPE degrading potential, with a recorded weight loss of 6.61 ± 0.25 % after 30 days of incubation. Followed by B2 with 3.58 ± 0.14 % and D1 with 1.21 ± 0.15 % weight loss (p < 0.05). SEM projected the change in the surface morphology of the LDPE piece, while FTIR revealed alterations in chemical bonding and structure, demonstrating the signs of LDPE degradation. In conclusion, both Rice Field and Beach Soils detected the presence of Actinomycetes, with three potential Actinomycetes with LDPE degrading properties. The isolated Actinomycetes could be further enhanced to expedite the LDPE degradation process, providing a sustainable solution for handling plastic waste.