Meet Zophobas morio

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In a latest attempt to tackle the plastic waste menace, scientists in Australia have discovered a commonly known superworm with the ability to survive on a diet of polystyrene.

Over 380 million tonnes of plastic are produced annually and according to the United Nations Environmental Programme more than 99 per cent of plastics are produced from chemicals derived from oil, natural gas and coal.

Crude oil is the raw material for making plastics. It is a non-renewable resource, so recycling plastic helps to conserve it. Recycling also stops plastic going to landfill sites or causing a litter nuisance. Different types of plastics have to be sorted out before recycling.

Thereby in one of the several attempts to recycle plastic, Australian scientists discovered that superworm Zophobas morio digests plastic through a gut enzyme while they note that this could be significant for advancements in recycling.

Superworms are like mini recycling plants, shredding the polystyrene with their mouths and then feeding it to the bacteria in their gut,” Dr Chris Rinke said.

The University of Queensland team fed three groups of superworms different diets over three weeks. The batch that ate polystyrene even put on weight. The team found several enzymes in the superworm’s gut have the ability to degrade polystyrene and styrene. Both are common in takeaway containers and other items such as insulation and car parts.

But the research is unlikely to lead to massive worm farms that double as recycling plants. Instead, they hope to identify which enzyme is the most effective so it can be reproduced at scale for recycling.

According to a research published in Microbial Genomics, plastic would then be mechanically shredded, before being treated with the enzyme.

 “The breakdown products from this reaction can then be used by other microbes to create high-value compounds such as bioplastics,” Dr Rinke said.

Research has previously shown some types of beetle larvae can consume polystyrene. But this study takes it a step further, Australian National University researcher Colin Jackson said.

“This study goes a long way towards understanding how the bacteria in gut of the superworm would do this at the molecular level,” Professor Jackson told the Australian Broadcasting Corporation.

Is it feasible?

Internationally, other researchers have had success in using bacteria and fungi to break down plastics.

But some question whether such techniques will ever be commercially viable.”The scale-up and translation of research like this is always a challenge, which is magnified in the area of plastics by the incredible scale of the problem and the economics in terms of how cheap new plastic is to produce,” Professor Jackson said.

If scientists can work out how to grow the gut enzyme in a lab, they could use it to dissolve plastics on a mass scale, forming these byproducts into bioplastics.

“We can then look into how we can upscale this process to a level required for an entire recycling plant,” said Co-author of the research, PhD candidate Jiarui Sun.

Given that polystyrene accounts for around one-tenth of all non-fibrous plastics, this would be a significant breakthrough.

The real viable solution 

Senior adviser to the Centre for Environmental Justice (CEJ), Hemantha Withanage observed that this could be yet another hypothetical research while observing that the real viable solution to plastic waste is putting an end to the production of plastic and resorting to more wise production mechanisms.

He added that recycling of plastic is in itself a myth as only two per cent of global plastic is being recycled with the total amount of plastic that goes through the upcycling, downcycling and recycling process amounts to 12 per cent whilst over 88 per cent of plastic is released to the environment.

Withanage observed that the practicality of the use of superworms to recycle global plastic waste could be an impending question.

Wax worm study

Previously, a study by Brandon University in Canada found that wax worms which normally live in beehives and eat wax, also can survive on polythene.

According to the Brandon University, as the natural diet of wax worms which is honeycomb is chemically similar to polyethylene, the wax worm may have evolved the necessary biochemical adaptations to degrade plastic waste.

In the lab, 60 of the wax worms were able to eat more than 30 square centimetres of a plastic bag in less than a week, the researchers report.

They observed that this research provides evidence that aspects of microbial and animal metabolism work together during polyethylene degradation. Enzymes from the animal and resident gut bacteria may be combined to develop a technology that may be used to degrade our plastic waste in the future. Further research should look at identifying and exploiting the enzymatic machinery involved in this pathway.

They noted Gene expression of the waxworm host revealed that many digestive processes of honeycomb-fed caterpillars were similar in polyethylene-fed larvae suggesting normal intestinal function on a plastic diet.

“ Polyethylene-fed larvae also showed a unique gene expression profile with an increased capacity for fat metabolism. Interestingly, a direct measurement of fat quantities also showed increased fat retention in polyethylene-fed larvae. This demonstrates that the wax moth larva also plays a role in polyethylene degradation in synergy with their microbiome. While their normal metabolism is geared towards deriving energy from bulky wax comb hydrocarbons, these pathways can be co-opted for the degradation of synthetic polymers like polyethylene,” University of Brandon researchers observed.

Despite the number of research carried out into the use of worms that devour plastic, focus of many have been on the complete prohibition of plastic production in order to minimise environmental pollution.

“Recycling plastic materials doesn’t work and is not the answer to threats to global oceans and marine wildlife, UK Prime Minister Boris Johnson said. Answering children’s questions ahead of the COP26 climate change summit, the Prime Minister said reusing plastics “doesn’t begin to address the problem”.

Instead, he said, “We’ve all got to cut down our use of plastic”.

( Source: BBC, Centre for Environmentalists Justice, Forbes, Euro News)

By Faadhila Thassim