Abstract
Milk is a significant foodstuff around the world, being produced and consumed in large quantities. The safe consumption of milk requires that the liquid has an acceptably low level of microbial contamination and has not been subjected to spoiling. Bacterial safety limits in milk vary by country but are typically in the thousands per mL of sample. To rapidly determine if samples contain an unsafe level of bacteria, an aptamer-based sensor specific to Escherichia coli bacteria was developed. The sensor is based on an ultra-high frequency electromagnetic piezoelectric acoustic sensor device (EMPAS), with the aptamer being covalently bound to the sensor surface by the anti-fouling linker, MEG-Cl. The sensor is capable of the selective measurement of E. coli in PBS and in cow’s milk samples down to limits of detection of 35 and 8 CFU/mL, respectively, which is well below the safe limits for commercial milk products. This sensing system shows great promise for the milk industry for the purpose of rapid verification of product safety.
Highlights
IntroductionMilk is a highly important foodstuff, with the European Union producing over 160 million tons of milk each year [1]
For milk to be safe for consumption it must be reasonably free of harmful microbes, such as Escherichia coli (E. coli) or Staphylococcus aureus (S. aureus), which could render illness in consumers
In the first series of experiments, we studied the kinetics of the changes in the frequency of the bare piezocrystal as well as those modified by antifouling MEG-Cl linker with attached DNA aptamers following interaction with various concentrations of E. coli in a PBS (Figure 1a) as well as in UHT cow’s milk (Figure 1b)
Summary
Milk is a highly important foodstuff, with the European Union producing over 160 million tons of milk each year [1]. For milk to be safe for consumption it must be reasonably free of harmful microbes, such as Escherichia coli (E. coli) or Staphylococcus aureus (S. aureus), which could render illness in consumers. Foodborne Shiga toxin-producing E. coli (STEC) can cause mild to severe clinical conditions, including acute gastroenteritis and hemolytic uremic syndrome [2,3]. In Europe, approximately 6% of STEC cases result from dairy consumption [2]
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