Friday, January 18, 2019

Promising Bioplastic Derived from “Poo Molecule”

A new, fossil-free bioplastic is emerging. According to lab experiments, it is more durable than both regular plastic and other bioplastics, and is potentially better suited for recycling.

Ping Wang 
Ping Wang (Photo: Theo Hagman-Rogowski)
Photo: Theo Hagman-Rogowski

Almost all plastic is made from crude oil, and plastic production currently accounts for 4-6% of global oil consumption. The development of renewable bioplastics is progressing, but relatively few are actually being used.

A strong candidate among bioplastics is polyethylene furanoate (PEF). Instead of oil, PEF contains the hydrocarbon, furan, which can be extracted from maize, wood and certain types of grain. The main market for PEF is packaging. Experiments have shown that PEF is superior to standard polyethylene terephthalate (PET) in protecting against oxygen, carbon dioxide and water, which gives products enclosed in plastic greater durability.

The success of PEF made researchers at Lund University interested in other renewable materials that could potentially be used for plastic production. Chemical engineering doctoral student Ping Wang has produced a plastic based on indole, a heavier hydrocarbon molecule than furan, that is present in human faeces and smells accordingly. The compound is also found in lower concentrations in certain flowering plants and has a more agreeable aroma. This effect is due to our sense of smell decoding the aroma differently depending on the amount and combination.

The research team is thought to be the only one researching indole polyesters, and their results are promising. A regular PET bottle’s glass-liquid transition temperature – when the material softens and deforms – is 70 degrees. The most successful PEF experiments withstand about 86 degrees. However, one of Ping Wang’s indole plastics is stable up to 99 degrees.

“These are preliminary results, but we have seen that polyester plastic has better mechanical properties, which makes it more sustainable. This can lead to better recycling in the future. At present, PET bottles can only be recycled once, then they must be used for something else such as textiles”, says associate professor Baozhong Zhang, who is supervising the research team.

Currently, indole is only produced on a small scale and used mainly in perfumes and drugs. It may be possible to use bioengineering methods to produce indole from sugar through fermentation. However, such a process would first need to be analysed more thoroughly before the production cost can be calculated.

Ping Wang is continuing her research by examining the indole plastic’s potential in other application areas.

“We obtained good results, but are not satisfied. Now we are trying to find methods for making higher quality indole polymers that can be used in more ways, not just for plastic bottles”, she concludes.





Contacts and sources:
Ping Wang
Lund University

Citation: Indole as a new sustainable aromatic unit for high quality biopolyesters



Body-Painting Protects Against Bloodsucking Insects

A study by researchers from Sweden and Hungary shows that white, painted stripes on the body protect skin from insect bites. It is the first time researchers have successfully shown that body-painting has this effect. Among indigenous peoples who wear body-paint, the markings thus provide a certain protection against insect-borne diseases.

Human models used in the experiment
Plastic human models lying in grass
Photo: Gabor Horvath


Most of the indigenous communities who paint their bodies live in areas where there is an abundance of bloodsucking horseflies, mosquitoes or tsetse flies. When these insects bite people there is a risk of bacteria, parasites and other pathogens being transferred.

The study shows that body-painting provides protection against the insects. A brown plastic model of a human attracted ten times as many horseflies as a dark model painted with white stripes. The researchers also found that a beige-coloured plastic figure used as a control model attracted twice as many bloodsuckers as the striped model.

Striped bodypaint was the most protective

Photo: Gabor Horvath

According to Susanne Åkesson, professor at Lund University’s Department of Biology, the tradition of body-painting may have developed simultaneously on different continents. It is not known when the tradition started.

“Body-painting began long before humans started to wear clothes. There are archaeological finds that include markings on the walls of caves where Neanderthals lived. They suggest that they had been body-painted with earth pigments such as ochre”, says Susanne Åkesson.

The research team has previously observed that the zebra’s stripes act as protection against horseflies. It is also known that pale fur, on horses for example, can provide protection, in contrast to dark fur. The discovery won the IgNobel Prize in Physics in 2016. In the new study, the team has taken the research a step further and examined plastic models that are the same size as adult humans.

Susanne Åkesson

Credit: Lund University 

For the experiments, which were conducted in Hungary, the researchers painted three plastic models of humans: one dark, one dark with pale stripes and one beige. They then covered the three models with a layer of insect glue. The dark model attracted ten times more horseflies than the striped model, and the beige model attracted twice as many as the striped one.

They also examined whether the attraction of horseflies differed between models that were lying down or standing up. The results show that only females were attracted to the standing models, whereas both males and females were drawn to the supine models.

“These results are in line with previous experiments in which we showed that males gravitate towards water in order to drink and land on surfaces that reflect horizontal, linear polarised light, such as signals from a water surface. Females that bite and suck blood from host animals respond to the same signals as the males, but also to light signals from in the vertical plane, such as the standing models”, concludes Susanne Åkesson.


Contacts and sources:
Susanne Åkesson
Lund University

Citation: Striped bodypainting protects against horseflies.
Gábor Horváth, Ádám Pereszlényi, Susanne Åkesson, György Kriska. Royal Society Open Science, 2019; 6 (1): 181325 DOI: 10.1098/rsos.181325