Klebsiella pneumoniae isolated from the intestines of Tenebrio molitor larvae (Coleoptera: Tenebrionidae) that consume expanded polystyrene

Plastics such as polystyrene are resistant to biodegradation, pollute the environment, and negatively impact the health of living organisms. However, several organisms, such as the larvae of Tenebrio molitor (Coleoptera: Tenebrionidae) and their associated gut microbiome, contribute to its degradation. The aim of this research was to determine the efficiency of degradation of expanded polystyrene (EPS) by gut bacteria isolated from larvae of T. molitor. To achieve this, a set of EPS-degrading bacteria was selected based on the time required to utilize the polymer as a carbon and energy source. Additionally, EPS degradation efficiency was compared, and the most efficient degrading bacterium was identified at the molecular level. Results showed that 95.13% of the bacteria isolated on nutrient agar and 86.57% of those isolated on MacConkey agar were able to grow on EPS. Five selected bacteria were able to degrade the polymer after 36 hours of incubation. The efficiency of EPS degradation, expressed as the percentage of weight loss by the degrading bacteria, ranged from 5.29% to 12.68%, with a reduction rate of 0.0005 to 0.0013 g per day and a half-life of 533.15 to 1386.20 days. Finally, 16S rRNA gene analysis identified the bacterium as Klebsiella pneumoniae. Cultivable gut bacteria from T. molitor larvae have demonstrated potential as candidates for EPS degradation, and biotechnological techniques can further enhance the efficiency of the degradation process.