‘Superworms’ Eat—and Survive on—Polystyrene

One of the noticeable things about Christian Rinke's laboratory is the loud crunching noise of worms chewing their way through styrofoam and into plastic foam. Rinke says he raises his ear to make sure he isn't late for work. He says you can hear it if the worm is still consuming it.

Rinke and his colleagues have been feeding plastic to Zophobas morio beetle larvae to see if they can offer insights into how to break down some of the plastic waste humans generate. Superworms can live on a diet of nothing but polystyrene, which is used in a wide range of products. The ability of the worms to process plastic suggests that it is broken down quickly in the stomach. According to Rinke, they are basically like eating machines.

The researchers split 135 superworms into three groups and fed them different types of food. The group of worms that were starving were isolated from each other. Over the course of three weeks, the Bran-fed larvae doubled their weight and were much healthier than the plastic-fed ones. Some of the worms were put aside to be beetles. Nine out of 10 worms were able to grow into beetles and maintain a diversity of gut flora. The plastic-fed larvae put on more weight than the starved worms and grew into beetles. Rinke says that polystyrene is not a good diet for the worms. It looks like they can get some energy out of the material.

It's possible that this is due to a relationship between a superworm and its gutbacteria. The worm shreds the plastic so thebacteria can biodegrade it and break it down into smaller Molecules that may be easier to digest. The golden ticket to replicating the process on a large scale in the future is knowing the exact type ofbacteria that break down the polystyrene. The new study needed to sequence the genomes of the worms. Rinke says that using metagenomics, they can identify all the genes in the gut. According to Rinke, previous studies of other insects focused on just one or two possible gutbacteria oramylases.

The head of the University of Greifswald in Germany has been waiting for these kinds of data for a long time. The first solid study where they looked into the metagenome was published in the new work.

Rinke and his colleagues were able to identify specific enzymes that they believed acted in a specific order to biodegrade the polystyrene in the superworms' gut. The team was told that they couldn't break the bonds between the carbon atoms in the plastic. The researchers are revising the steps they proposed due to feedback.

Rinke and his colleagues are not suggesting that superworms should be released into landfills or polluted landscapes to rid them of plastic, but that the worms' unique gut microbiome may hold a key to developing a chemical process to biodegrade the material. They have a lot of work to do. They plan to use their metagenomic data to try to find the most efficient way to break down our plastic waste.