Dataset Information

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.

SUBMITTER: Machona O

PROVIDER: S-EPMC8728996 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:Abstract Tenebrio molitor, a species of darkling beetle, is capable of metabolizing expanded polystyrene (EPS), a durable single-use plastic, when in its larval stage, mealworms. EPS consumption studies were conducted on mealworm, beetle, and co-culture habitats with a one-week acclimation period and a three-week experimentation period to compare the EPS consumption rate at each stage. Subsequent experiments tested various beddings (oats, beads), supplemental nutrients (spinach, protein powder paste, cucumbers, lemon slices), and EPS pre-treatments (lemon-lime soda, lemon juice, tomato paste) to determine the effect of those variations on mealworm EPS consumption. It was concluded that one mealworm consumes EPS at least fifty times faster than one beetle. EPS biodegradation rates were estimated under the assumption that 48.2% of consumed EPS was biodegraded by mealworm gut bacteria into carbon dioxide and biomass. It was found that EPS biodegradation rates increased 34.8% in habitats with inedible bead beddings compared to those with an edible oat bedding. EPS biodegradation rates by mealworms were also seen to increase 482% in habitats where the EPS was pre-treated with lemon-lime soda and 125% in habitats with a spinach supplemental nutrient compared to EPS biodegradation rates in a habitat with no supplemental nutrient or pre-treatment. Each supplemental nutrient and EPS pre-treatment variation in an individual inedible bead bedding improved the mealworm consumption rate of EPS. It was determined that approximately four mealworms could degrade EPS at least as quickly as natural biodegradation. These findings suggest that habitat conditions strongly affect EPS consumption rates by mealworms. Highlights • Mealworm consumption rates of EPS are fifty times greater than those of beetles. • Mealworm EPS consumption rates are lower in edible beddings than inedible beddings. • EPS consumption rates by T. molitor improved with cups pre-treated in acidic media. Supplementary Information The online version contains supplementary material available at 10.1007/s40710-021-00556-6.