25 December 2015

Plastic-Eating Insects

Welcome back. Do you remember my blog post about dining on insects (Entomophagy)? Right, you’d rather not remember. Anyway, I didn’t write a lot about the delights of mealworms, thinking that cooking with flour made from crickets would be more palatable to anyone like me who’s new to the topic.

But today is this blog’s Mealworm Appreciation Day. First, because the little crawly creatures are way up there on the global menu. Second, because they’re a big seller as insect-eating pet food and bait for fishing. And third--yes, research has given us a new reason, which could be the most important:

Mealworms can biodegrade Styrofoam, a polystyrene product thought to be non-biodegradable. Understanding how a mealworm’s internal microorganisms--its gut bacteria--accomplish this task could lead to new approaches for managing plastic waste.

The darkling beetle–mealworm
life cycle. (Multiple websites)
(If it makes you feel any better about them, mealworms aren’t worms. They’re larvae that spend from 30 to 90 days before they pupate and later emerge as darkling beetles. Sorry, not butterflies.)

Mealworms Dispose of Polystyrene

Collaborating researchers from the PRC’s Beihang University and BGI–Shenzhen (formerly Beijing Genomics Institute) and Stanford University recently published two companion papers on the mealworms’ ability to biodegrade and mineralize polystyrene. The first paper focused on the mealworms and Styrofoam byproducts; the second examined the role of gut microorganisms.

Mealworms eating Styrofoam.
In their laboratory study, the researchers found that 100 mealworms devoured 34 to 39 milligrams of Styrofoam--picture a small pill--in 24 hours. 

Within a 16 day test period, the mealworms converted nearly 48% of the ingested Styrofoam into carbon dioxide (as they would any food source), excreted just over 49% as biodegraded polystyrene fecal matter and incorporated about 0.5% into biomass.

Over the course of one month, mealworms fed only Styrofoam appeared to be as healthy as mealworms fed the normal diet of bran. Moreover, their fecal matter seemed to be as safe to use as soil for crops.

In-depth analysis of mealworm gut bacteria confirmed the presence and essential role of polystyrene-degrading gut bacteria.

Wrap Up

Research on reducing plastic waste didn’t begin with these studies, yet their success led the researchers to pose spinoff research questions. 

For example, can the gut bacteria in mealworms or other insects biodegrade other plastics? How would other animals fare if they dined on Styrofoam-fed mealworms, and how would the degraded plastic track through the food chain? Are there marine analogs to mealworms that might take a bite out of our plastic-strewn oceans? What conditions are favorable to plastic degradation and what more can be learned about enzymes for breaking down polymers to advance plastic degradation?

Well? Now what do you think about mealworms? Thanks for stopping by.


Research papers on plastic-eating mealworms in Environmental Science and Technology journal:
Stanford University news release on mealworm studies:
Article on mealworm studies on Discovery website:

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