科研之友
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摘要
To circumvent the strictly regulated limits of antibiotics in milk, illegal addition of beta-lactamase to lower the antibiotic levels in milk has been reported recently in China. Herein, we describe a fast, sensitive, and robust HPLC-UV method for the determination of beta-lactamase activity in milk, based on an indirect quantification strategy. The test milk sample was mixed with a known amount of penicillin G, a specific substrate of beta-lactamase. After incubation, an aliquot of the mixture was injected into the HPLC-UV system to quantify the remaining penicillin G in less than 10 min. Comparative analysis of the amount of penicillin G before and after incubation was used to indirectly deduce the activity of beta-lactamase in the test sample. This method was successfully applied to milk products with different fat percentages, resulting in a detection limit of 0.6 U/mL. Good recoveries, ranging from 94 to 105%, were obtained from blank milk samples spiked with beta-lactamase at levels of 2 to 50 U/mL, with relative standard deviations <6%. A good correlation was demonstrated between the HPLC method and the conventional culture-based assay. Using this method, the activity changes in beta-lactamase during milk pasteurization, sterilization, and storage were investigated. The advantages of low-cost, accurate quantification and easily accessible instrumentation make the proposed method an ideal alternative for high-throughput routine analysis in the dairy industry.
- 出版日期2015-4
- 单位国家食品安全风险评估中心
