‘Living’ bacterial biosensor gives wine spoilage detection a glow-up
How can you tell if your wine has spoiled? This new ‘living biosensor’ will give you a glowing heads up.
A bacterial biosensor created by researchers from The Hebrew University of Jerusalem (Rehovot, Israel) lights up in the presence of acetic acid – a by-product of alcoholic fermentation and surefire sign that wine is starting to go off. The new technology could be scaled up for industrial purposes, offering a simple, low-cost option for real-time acetic acid monitoring that ensures timely intervention before spoilage occurs.
Acetic acid accumulation can disrupt the fermentation process and cause the alcoholic beverages produced to spoil, rendering them undrinkable. In the wine industry specifically, the buildup of acetic acid increases volatile acidity and produces a sour, vinegar-like taste. Monitoring the levels of this organic compound is, therefore, of great importance to human health and also commercial production.
Unfortunately, conventional methods for achieving this – such as steam distillation, gas chromatography and high-performance liquid chromatography – are expensive, time-consuming and impractical, making it difficult for wineries to keep tabs on and respond to acetic acid levels in real time. Alternative options include electronic noses and optical sensors, although these are limited by their sensitivity to ethanol, technical complexity and instability under fermentation conditions.
In search of a simpler solution, scientists developed a genetically encoded whole-cell biosensor that glows in response to acetic acid. They engineered Escherichia coli to express YwbIR, a LysR transcriptional regulator from Bacillus subtilis. Firstly, the team created a plasmid that contained the ywbIR gene upstream of luxCDABE genes, which encode the luciferase reporter, under the control of the native responsive bi-directional promoter, PywbI.
Following transformation into E. coli, in the presence of acetic acid, ywbIR and the luciferase reporter genes are transcribed, resulting in a measurable luminescent signal.
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Putting their new system to the test, the researchers measured luminescence against several concentrations of acetic acid, demonstrating that the biosensor has high sensitivity and a strong, linear response to acetic acid levels between 0 and 1 gram per liter, as well as a five to eightfold increase at wine spoilage-relevant concentrations. Moreover, the sensor remained functional even in ethanol concentrations as high as 14.5%.
Exposure of immobilized biosensor culture to the headspace of wine samples confirmed that it is capable of detecting volatile acetic acid in the air above the wine, making it a useful tool for identifying wine spoilage.
To the best of the researchers’ knowledge, “this is the first bacterial biosensor capable of headspace detection of [acetic acid] in wine, offering a cost-effective, scalable and real-time solution for industrial fermentation and food safety applications.”
Beyond just a win for winemaking, the sensor could have medical applications, such as in breath analysis, the team explains.
“It opens the door to affordable, on-site monitoring of fermentation quality and, in the future, may even support medical diagnostics based on volatile biomarkers,” Yael Helman commented.