Evaluation of low-density polyethylene degradation using a new thermophilic bacterial isolate

In this study a thermophilic bacterium was isolated and assessed its potential for degrading low-density polyethylene (LDPE) using polyethylene as carbon source. The bacterial isolate was capable of growing at 65 °C and demonstrated biofilm formation on LDPE. After 150 days of exposure to plastic, cell viability was confirmed and altered the physicochemical properties of the polymer. These changes included increased hydrophilicity, an increase in the carbonyl index (0.048 to 0.12), reduced crystallinity, a reduction of M¯_w (75 %) and M¯_n (68 %) values, release of degradation products (C16-C27), and evidence of surface degradation (holes, cracks, peeling) and an increase in surface roughness (36.87 %). With tryptone addition, it stimulated the growth and resulted in signs of LDPE surface degradation after 60 days. Degradation products, such as short- and medium-chain alkanes (C4-C20), caproic acid, and valeric acid were also found. The reduction of M¯_n and M¯_w was 51 % and 12 %, respectively. Phylogenetic analysis of whole genome sequencing showed that isolate had 98.94 % similarity to Parageobacillus caldoxylosilyticus. Therefore, it was named Parageobacillus caldoxylosilyticus strain BacLDPE. The present study showed the potential of the thermophilic isolate to degrade LDPE and perspectives for different plastic types.