Caterpillars of the wax moth love eating plastic: Fraunhofer LBF investigates degradation process
Can caterpillars be used to combat excessive plastic waste? Researchers at the
Fraunhofer Institute for Structural Durability and System Reliability LBF have
taken a closer look in an attempt to answer this question. The initial situation:
larvae of the wax moth Galleria melonella are thought to eat and digest
polyethylene, which is why they are considered to contribute to the CO2-
neutral elimination of the mountains of plastic waste that are growing
worldwide. However, whether the caterpillar can do this is still not understood
and is currently the subject of controversial discussion.
Within the Framework of a research project on the chemical imaging analysis of plastic digestion in caterpillars (RauPE), a team from Fraunhofer LBF used high-resolution Raman microscopy and dedicated software to follow the path of the plastic through
the caterpillar and made important contributions to clarifying These unanswered questions.
According to a study published in early 2019, larvae of the wax moth Galleria
melonella consume polyethylene (PE) and convert it at a remarkable rate: 100,000
caterpillars eat about 5.2 kilograms of PE within one week. This would open up
promising possibilities for the disposal and elimination of large quantities of plastic
waste. However, before this remarkable ability of the caterpillar can be harnessed
technologically, it must be clarified whether it actually digests the PE or merely crushes
and excretes it.
Own software decomposes Raman spectra
PE digestion by wax worms was the question pursued by the team at Fraunhofer LBF
within the RauPE project by using state-of-the-art, high-resolution Raman microscopy.
During the course of the project, the team has also developed dedicated software for
Raman microscopy of mixtures in Python. With the help of machine learning, it can
separate the superimposed Raman spectra of the components. It provides the spectra
of the individual components on the one hand and their local concentration on the
other. This enables researchers to detect even low concentrations of a substance, such
as PE, within a complex mixture.
The combination of Raman microscopy and software is able to spatially visualize low
concentrations of plastics within a mixture of different organic substances as they ocurr
within the caterpillar. This is possible in three dimensions with a resolution of up to one micrometer (0.001 mm). By using confocal optics, scientists can study caterpillars nondestructively, i.e. largely without preparation.
No biodegradation of polyethylene proven – further efforts necessary
The results so far have amazed the project team: caterpillars eat holes into PE foil, take
in small amounts of it and at the same time lose considerable body mass. Once there
are holes, the caterpillars stop further material intake. The analytical measurement data
does not provide any evidence that the caterpillars digest the polyethylene: »The fact
that caterpillars biodegrade polyethylene remains a visionary goal for the time being,
and intensive interdisciplinary efforts are essential to achieve it. For scientific research, it
is therefore all the more important to avoid and recycle plastic waste, taking into
account all stages along the packaging value chain,« emphasizes Dr. Bastian Barton,
who supervised the research project at Fraunhofer LBF. There is an urgent need for
improved concepts and suitable technologies for the production of post-consumer
plastics with high quality and constant availability. Only then would it be possible to
reuse plastics already in use on a large scale and for a wide range of products, Barton
Dr. Bastian Barton, firstname.lastname@example.org