Human-like e-nose to sniff out bacteria in water

Scientists are developing a bio-electronic nose mimicking that of a human which can detect bacteria in water by smelling it without the need for complex equipment and testing.
The sensor is simple to use and it can detect tiny amounts of contamination in water, making it more sensitive than existing detection methods, researchers said.
There are two main problems caused by bacteria and other microbes in water: they can make the water toxic, and make it smell bad.
At high concentrations, bacteria can be toxic in drinking water. But at lower levels - virtually undetectable by current culturing techniques - they can put people off from drinking it.

The new study shows how technology that mimics the human nose can sniff out low levels of bacteria and other microbes by detecting the "off flavour" they give off.
"Water that smells bad isn't necessarily toxic," said Professor Tai Hyun Park from Seoul National University, who led the study.

"Imagine you don't do your laundry; it's not that toxic but you don't want to wear it because the smell is bad. With drinking water, if there's off flavour, even if the water isn't toxic, you don't want to drink it. We wanted to develop a way to detect and remove this kind of contamination, so people are happy to drink water," said Park.

Traditionally, water was tested for contamination with bacteria by taking a sample and trying to grow the bacteria in the lab.
Park and the team wanted to develop a more convenient, compact device for testing water that is suitable for using on-site.
Humans have five senses - sight, hearing, touch, smell and taste. Among these five senses, we have devices that catch the information for three of them: sight, hearing and touch. But there is not yet a device that successfully captures information for smell or taste.
Bacteria that contaminate water give off particular smells that are associated with a handful of smell molecules.

Two typical odours - earthy and musty - are caused by two different molecules: geosmin (GSM) and 2-methylisoborneol (MIB).
The new nose-like device can detect these smells at very low concentrations of just 10 nanogrammes per litre of water. It's also very sensitive, and can spot a particular smell in a cloud of others.
The human nose is more complicated than receptors for two smell molecules, so to make a true smelling device, the researchers will need to scale up their efforts.
The study was published in the journal Biosensors and Bioelectronics.