## 3 Results
### Detection of LDPE Biodegradation Assay
#### 3.2.4 Gs-Ms Analysis
Several studies have claimed that weight loss is the initial stage of polythene degradation. The finding that showed a significant reduction in LDPE weight at 8.1% and 18.85% due to the activities of APCK5 and APCZ14, respectively, is consistent with previous studies [52]. It has recently been reported that _P. aeruginosa_ V1 showed the most significant degradation of LDPE, with a percentage weight loss of 18.21% [55]. In order to use the carbon and energy contained inside these complex molecules, microorganisms release a variety of enzymes that first break them down into simpler building blocks [56], which are then consumed as carbon sources. Consequently, a weight reduction in the LDPE is generated [40]. The pH and weight decrease confirmed that both isolates could utilize LDPE as their sole carbon source. Since FTIR is sensitive to the local molecular complexes, it has been widely used to evaluate the interactions between macromolecules during the process of LDPE breakdown. This is because of the sensitivity of FTIR to the local molecular environment [57]. FTIR analysis was used to monitor damage to the quality of the material by many physical and chemical processes and the structural transformation of LDPE, leading to the degradation of the polymer [1]. The structural alterations of the LDPE were assessed using Fourier transform infrared (FTIR) analysis to further monitor the biodegradability via the bacterial isolates APCK5 and APCZ14 [57]. The FTIR is the approach that is used to evaluate the changes in polyethene bonds and chemical composition. When compared with the control, the treated LDPE exhibited a change, as well as a new peak, which was validated by FTIR. LDPE treated with APCK5 and APCZ14 developed new peaks at (a) 1650 cm\({}^{-1}\) corresponding to the formation of double bonds; (b) 1715 cm\({}^{-1}\) corresponding to the formation of acids; and (c) 1740 cm\({}^{-1}\) corresponding to the formation of ketone, suggesting that the formation of chemically distinct intermediates during the biodegradation process. A comparable profile of LDPE spectra was obtained by [58], who found new peaks at 1250.33 cm\({}^{-1}\) and 1246.44 cm\({}^{-1}\), which correspond to the C-O stretching of esters groups in _Methylobacterium radiotolerans_ and _Lysinibacillus fusiformis_, respectively [58]. When a hydrogen atom on a long carbon-carbon bond is replaced by an oxygen atom, functional groups such as ester groups, carbonyl groups, and ether groups can be generated [59]. Interestingly, it has been reported that alkane hydroxylases play a pivotal role in aerobic alkane degradation via the formation of primary and secondary alcohols by hydroxylation of carbon-carbon bonds [60]. Furthermore, epoxidation of alkenes by microbial alkene monooxygenase leads to the formation of ether during LDPE biodegradation [61]. Based on these findings, it can be suggested that a change in peak position, the appearance of new peaks, or the disappearance of already existing ones are all indications of structural alterations in LDPE caused by degrading microorganisms. For further confirmation of LDPE biodegradation, GC-MS was applied. GC-MS appears to be the most effective technique for identifying volatile degradation products [62]. Dominant products were butylated hydroxytoluene, heneicosane, and 2,4-di-tert-butylphenol (Figure 6). The presence of these compounds proves the decomposition of LDPE; a similar order was reported by [63; 64]. In general, similar GC-MS profiles to our study have been reported by [65] for _Aspergillus nomius_ and _Streptomyces_ sp. and by [66] for _Bacillus licheniformis_ SARR1. Nonetheless, the compounds obtained might be the same or unique to the microbial group. Furthermore, a varying number of biodegraded compounds of polyethylene was obtained due to the action of various microbial groups. For example, six and eight compounds were detected after incubation with _Aspergillus nomius_ and _Streptomyces_ sp., respectively, for 90 days [65].