title: A novel thermometric biosensor for fast surveillance of β-lactamase activity in milk.
abstract: Regulatory restrictions on antibiotic residues in dairy products have resulted in the illegal addition of β-lactamase to lower antibiotic levels in milk in China. Here we demonstrate a fast, sensitive and convenient method based on enzyme thermistor (ET) for the surveillance of β-lactamase in milk. A fixed amount of penicillin G, which is a specific substrate of β-lactamase, was incubated with the milk sample, and an aliquot of the mixture was directly injected into the ET system to give a temperature change corresponding to the remained penicillin G. The amount of β-lactamase present in sample was deduced by the penicillin G consumed during incubation. This method was successfully applied to quantify β-lactamase in milk with the linear range of 1.1-20 UmL(-1) and the detection limit of 1.1 UmL(-1). The recoveries ranged from 93% to 105%, with relative standard deviations (RSDs) below 8%. The stability of the column equipped in ET was also studied, and only 5% decrease of activity was observed after 60 days of use. Compared with the conventional culture-based assay, the advantages of high throughput, timesaving and accurate quantification have made this method an ideal alternative for routine use.
authors.affiliation: China National Center for Food Safety Risk Assessment, Key Laboratory of Food Safety Risk Assessment, Ministry of Health, Beijing 100021, PR China. szhoupku@gmail.com
authors.forename: Shuang
authors.initials: S
authors.lastname: Zhou
authors.forename: Yunfeng
authors.initials: Y
authors.lastname: Zhao
authors.forename: Michael
authors.initials: M
authors.lastname: Mecklenburg
authors.forename: Dajin
authors.initials: D
authors.lastname: Yang
authors.forename: Bin
authors.initials: B
authors.lastname: Xie
mesh_terms: D000818:Animals; D000900:Anti-Bacterial Agents / Q000378:metabolism; D015374:Biosensing Techniques / Q000379:methods*; D057075:Enzyme Assays / Q000379:methods; D057230:Limit of Detection; D008892:Milk / Q000737:chemistry / Q000201:enzymology*; D010400:Penicillin G / Q000378:metabolism; D001618:beta-Lactamases / Q000032:analysis* / Q000378:metabolism*
chemical_list: D000900:Anti-Bacterial Agents; D001618:beta-Lactamases; D010400:Penicillin G
keywords: Antibiotics; Enzyme immobilization; Enzyme thermistor; Milk; β-lactamase