A new species of darkling beetle larvae that degrade plastic

Therefloats an enormous plastic garbage island in the North Pacific that is seventimes the size of the Korean Peninsula. The island, called the Great PacificGarbage Patch, is the result of 13 million tons of plastic that flow into theocean annually from the 20,000 units of plastic consumed per second aroundthe world. Plastic takes decades to hundreds of years to decompose naturallywith plastic bags taking 10 to 20 years, nylon products or disposable straws 30to 40 years, and plastic water bottles -- commonly used once then thrownaway -500 years to decompose. This problem of plastic, which has been labeled ahuman disaster, has been recently proven to be decomposable by beetles commonin Korea.

A jointresearch team consisting of Professor Hyung Joon Cha and a doctoral studentSeongwook Woo of the Department of Chemical Engineering at POSTECH with ProfessorIntek Song of Andong National University has uncovered for the first timethat the larvae of the beetle in the order Coleoptera (Plesiophthophthalmusdavidis) can decompose polystyrene, a material that is tricky to decompose. By2017, 8.3 billion tons of plastic waste were produced across the globe, ofwhich less than 9 percent were recycled. Polystyrene, which accounts forabout 6% of total plastic production, is known to be difficult to decompose dueto its unique molecular structure.

The researchteam found that the larvae of a darkling beetle indigenous to East Asiaincluding the Korean peninsula can consume polystyrene and reduce both its massand molecular weight. The team also confirmed that the isolated gut flora couldoxidize and change the surface property of the polystyrene film. Meanwhile, theresearch team isolated and identified Serratia from the intestinal tract of P.davidis larvae. When polystyrene was fed to the larvae for two weeks, theproportion of Serratia in the gut flora increased by six fold, accountingfor 33 percent of the overall gut flora. Moreover, it was found that the gutflora of this larvae consisted of a very simple group of bacterial species(less than six) unlike the gut flora of other conventional polystyrene-degrading insects.

The uniquediet of the darkling beetle larvae that was uncovered in this study presentsthe possibility that polystyrene can be broken down by other insects that feedon rotten wood. In addition, the development of an effective polystyrene-decomposingflora using the bacterial strains found in the simple gut flora of P. davidisis highly anticipated. The study is also noteworthy in that the paper's firstauthor, Seongwook Woo, who has been interested in insects since childhoodand wished to make the world a better place through them, sought outProfessor Cha as soon as he entered POSTECH and focused on research under hissupervision over the years.

As thecorresponding author of the paper, Professor Cha commented, "We havediscovered a new insect species that lives in East Asia -- including Korea --that can biodegrade plastic through the gut flora of its larvae." Heconcluded, "If we use the plastic-degrading bacterial strain isolatedin this study and replicate the simple gut floral composition of P. davidis,there is the chance that we could completely biodegrade polystyrene, which hasbeen difficult to completely decompose, to ultimately contribute tosolving the plastic waste problem that we face."

Theseresearch findings were recently published in the online edition of Applied andEnvironmental Microbiology, a long-standing authoritative journal in appliedand environmental microbiology.

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Materialsprovided by Pohang University of Science & Technology (POSTECH). Note:Content may be edited for  style and length.