TEST what you can't TASTE.
Antibiotic injection is a common practice in dairy farms as a way to prevent mastitis in cow’s lactation period. But human’s long-term consumption of milk with excessive amount of antibiotics, can pose severe health threats.
In rural areas of China, milk goes directly to consumers without being tested for antibiotic residues, part of this is because currently used detection methods are either unreliable or not cost-effective enough to be accessed easily. Therefore we work to develop a cheap penicillin detection method, so that it can be used in relatively underdeveloped areas, and people in China could take one step closer to having an equal chance to qualified milk.
To gain a better understanding of how our project can help improve the situation of antibiotic residues in China, we interviewed Dr. Meng Lu from Chinese Academy of Agricultural Science for more information, and visited the plant of Sanyuan Milk Group, one of China’s largest dairy processing companies. We integrated our research and outreach to the optimization of our project, hoping to lessen the inequality between rural and urban residents’ access to qualified milk.
1.0 We engineer our bacteria to generate Penicillin Binding Protein 5-Green fluorescence Protein (PBP5-GFP), and bind penicillin to the coated wells on the ELISA plate. The protein is added to the sample, where the penicillin in the sample compete for PBP5-GFP with those on the plate, and the fluorescence intensity in the sample is measured and reflects its penicillin concentration.
2.0 PBP5 causes the hydrolysis of tripeptide Lys-Ala-Ala(KAA) when active and not bound with penicillin, releasing one alanine and exposing one amino group. We measure its hydrolysis by the amino group, which changes the color of KAISER, a substance that reacts with free amino acids to yield CO2, NH3, and an aldehyde, the NH3 further yielding a colored product (diketohydrindylidene-diketohydrindamine, a bi-indanedione derivative also called Ruhemann purple), yielding the color purple. With more penicillin present, more PBP5 becomes inactive, and the purple gets lighter.