The cardboard sensors incorporate a process known as laser scribing, in which a laser is used to convert a small amount of the cardboard into carbon, making it electrically conductive.
The research team also used gold nanoparticles, which further improve the sensor’s response by decreasing the material’s resistivity.
Taking this approach means the sensor can detect the metabolic activity of bacteria via a chemical reaction that confirms the probiotic has oxidised a molecule.
“We were interested in developing a low-cost tool to evaluate the metabolic activity of various probiotics,” said Dr Carlos D Garcia, study team member and professor in chemistry at Clemson University, in South Carolina.
“The main reason for this is that probiotics can only provide health effects when the microorganisms are alive, meaning they’re metabolically active and interacting with the host’s body.
“So, the type of probiotic, its formulation, and how it’s processed become critically important.”
Beer bacteria found to be more metabolically active than bacteria found in yoghurts
The study, which was published in the journal Analysis and Sensing, tested both beer and yoghurt and found that the sensors could determine the metabolic activity more accurately than other tests currently available.
The researchers also found that bacteria in the beer, an unfiltered India pale ale (IPA), had more metabolic activity than the yoghurts, which were popular brands Siggi’s, Yakult, and Activia.
They also noted that the sensor only measured total metabolic activity of microorganisms in the sample and did not indicate anything about the type of activity or potential health effects.
“Addressing specific medical needs is still outside the scope of our project,” said Garcia. “There is not a lot of research linking specific probiotics with specific diseases.
“Most of the current literature points to the overall advantages of probiotics. Recent studies have found that probiotics may prevent the development of harmful bacteria in the body, lower cholesterol levels, reduce constipation, control blood pressure, enhance the production of vitamins, improve calcium absorption, and boost the immune system.”
Possible limits to consuming the probiotics found in beer and supplements
While a number of research groups have reported on the potential health benefits of beer, not all beers will provide these benefits.
A pint of IPA carries beneficial bacteria; however, this is offset by an alcohol content of between 6 and 8% and a calorie count of 180 to 200 kcal.
The researchers added that studies using more traditional probiotic foods, which contain many of the microorganisms in the gut, have found that probiotics’ ability to correct specific health issues is “probably limited”.
Also, considering the way supplements containing probiotics are regulated, it is hard to say whether the products definitely contain the type and number of viable bacteria advertised on the label.
The team went on to describe the use of the sensor as providing a simple, portable, and low-cost way to detect the activity of live bacteria. These sensors could one day be used in fields such as healthcare.
Indeed, Garcia revealed that the team have used the same detection strategy for a number of microorganisms, including harmful pathogens such as Staphylococcus aureus.
A wealth of opportunities to couple chemistry with artificial intelligence
Looking ahead, the tool may also be used to help weigh up the benefits, demands, and risks of ingredients, as well as their role in nutrition and immunity, and especially gut health.
“This is something we would love to explore,” said Garcia. “We believe there are lots of opportunities to couple chemistry with artificial intelligence.
“Our lab is starting to explore those with the prediction of antioxidant synergism and the formation of natural deep eutectic solvents (NADES).We hope to expand our work to the sensors side soon.”
