Enhancing the biodegradation of low-density polyethylene (LDPE) using novel bacterial consortia: Bacillus sp. AS3 and Sphingobacterium sp. AS8.

Pretreatment of Low-Density Polyethylene (LDPE) with physicochemical methods before biodegradation has been demonstrated as an effective strategy. The pretreatment of LDPE exhibited alterations in molecular structure, reducing hydrophobicity and decreasing tensile strength. Additionally, pretreating LDPE enhanced microbial biodegradability to improve biofilm formation and significantly reduced the physical weight of LDPE film. AS3-8 consortia exhibited a maximum weight loss of 8.0 % ± 0.5 % after 45 days of incubation. While Bacillus sp. AS3 and Sphingobacterium sp. AS8 demonstrated LDPE weight loss of 5.03 % ± 1.6 % and 1.6 % ± 0.5 %, respectively. The structure of LDPE was altered after incubation with the bacterial strains, resulting in a reduction in the intensity of functional groups, including C=O, C=C, N-H, and C-N. The carbonyl index (CI) of LDPE also decreased by 7.17 % after the consortia AS3-8 degradation. Consortia AS3-8 significantly impacted the physical properties of LDPE by reducing the water contact angle (WCA), decreasing to 64.21° ± 3.69°, and tensile strength (TS), decreasing to 17.97 ± 0.3 MPa. Moreover, the esterase activity was measured through 45 days of incubation. SDS-PAGE analysis of the AS3-8 consortia revealed bands at 35, 48, and 70 kDa molecular weights, similar to known enzymes like laccase and esterase. Furthermore, SEM observations showed rough, cracked surfaces on pretreated LDPE, with biofilms present after incubation with the bacterial strains. GC-MS analysis revealed that AS3-8 consortia produced depolymerized chemicals, including alkanes, aldehydes, and esters. The LDPE biodegradation pathway was elucidated. This study addresses critical knowledge gaps in improving plastic degradation efficiency.