Tenebrio molitor: possible source of polystyrene-degrading bacteria

Abstract

Background The excessive use of polystyrene as a packaging material has resulted in a rise in environmental pollution. Polystyrene waste has continually increased water pollution, soil pollution and the closing of landfill sites since it is durable and resistant to biodegradation. Therefore, the challenge in polystyrene disposal has caused researchers to look for urgent innovative and eco-friendly solutions for plastic degradation. The current study focuses on the isolation and identification of bacteria produced by the larvae of beetle Tenebrio molitor (yellow mealworms), that enable them to survive when fed with polystyrene foam as their sole carbon diet. Materials and methods The biodegradation of polystyrene by Tenebrio molitor was investigated by breeding and rearing the mealworms in the presence and absence of polystyrene. A comparison was made between those fed with a normal diet and those fed on polystyrene. The mealworms which were fed with polystyrene were then dissected and the guts were collected to isolate and identify the bacteria in their guts. The viability and metabolic activity of the isolates were investigated. The polymerase chain reaction (PCR) followed by sequencing was used for molecular identification of the isolates. The PCR products were directly sequenced using Sanger’s method and the phylogenetic tree and molecular evolutionary analyses were constructed using MEGAX software with the Neighbour Joining algorithm. The evolutionary distances were computed using the Maximum Composite Likelihood method. Results The decrease in mass of the polystyrene as feedstock confirmed that the mealworms were depending on polystyrene as their sole carbon diet. The frass egested by mealworms also confirmed the biodegradation of polystyrene as it contained very tiny residues of polystyrene. Three isolates were obtained from the mealworms guts, and all were found to be gram-negative. The sequencing results showed that the isolates were Klebsiella oxytoca ATCC 13182, Klebsiella oxytoca NBRC 102593 and Klebsiella oxytoca JCM 1665. Conclusion Klebsiella oxytoca ATCC 13182, Klebsiella oxytoca NBRC 102593 and Klebsiella oxytoca JCM 1665 maybe some of the bacteria responsible for polystyrene biodegradation.

Molecular Detection and Phylogenetic Analysis of the alkB Gene in Klebsiella oxytoca Strains Isolated from the Gut of Tenebrio molitor

“…Because the polystyrene emulsion provided the nutrients, only microorganisms capable of feeding on polystyrene and thus responsible for polystyrene degradation were able to grow on the culture plates. The microorganisms isolated from the guts of Tenebrio molitor were confirmed to be Klebsiella oxytoca strains which have previously been isolated using the polymerase chain reaction (PCR) method [ 6 ]. Primers that amplify the 16S ribosomal RNA region in each of the isolates were designed to confirm that the bacteria were of Klebsiella oxytoca strains Klebsiella oxytoca ATCC 13182, Klebsiella oxytoca JCM 1665, and Klebsiella oxytoca NBRC 102593 using the provided sequences [ 6 ].…”

“…Primers that amplify the 16S ribosomal RNA gene in these bacterial strains were designed using the sequences of the 16S ribosomal RNA gene for the three bacterial strains. The sequences used to design the primers were previously reported [ 6 ]. To design the primers, the NCBI primer blast tool ( https://www.ncbi.nlm.nih.gov/tools/primer-blast/index.cgi ) was used.…”

“…These bacterial species were Serratia marcescens , Klebsiella oxytoca , and Pseudomonas aeruginosa . In a more recent study, three bacterial isolates identified as Klebsiella oxytoca NBRC 102593 strain , Klebsiella oxytoca JCM 1665 strain, and Klebsiella oxytoca ATCC 13182 strain were isolated from T. molitor mealworms which were fed solely on polystyrene for 7 days [ 6 ]. From this study, it was then concluded that the Klebsiella oxytoca species are among the species responsible for the biodegradability of waste-expanded polystyrene by Tenebrio molitor mealworms.…”

Starvation Effects on Superworms: Implications in Identifying Plastic-Degrading Genes and Microbes

“…Enterococcus mundtii has been reported to degrade hydrocarbons, which are the intermediate metabolites of PE. The microorganisms whose proportion increased in the PE-fed group showed a strong correlation with degradation of plastics or their metabolites (Lou et al, 2020;Machona et al, 2022;Patel and Shah, 2023). Including the Starved group as a control enhanced the precision in assessing microbial changes induced by plastic consumption.…”

Biodegradation of Expanded and Extruded Polystyrene with Different Diets by Using Zophobas atratus Larvae (Coleoptera: Tenebrionidae)

“…acts mutualistic relationship with insect hosts by digesting food in the gut and providing nutrients to the host (Sun et al, 2022). Besides, Machona et al (2022) mentioned that Klebsiella sp. can degrade polystyrene in the gut system of T. molitor.…”