Abstract:

Using sodium alginate-starch gel as a fixing agent, lactobacilli were immobilized between two nuclear
microporous membranes to make a sandwich-type sensing membrane, which was then fixed to a glassy carbon electrode
to make a biosensor electrode. Based on the current responses of three antibiotics at different concentrations tested by
electrochemical workstation, the calculation results showed that the most appropriate quantity of lactobacilli fixed by
the sensor was 0.05 g, and now the limits of detection concentration (LDC) of the biosensor for penicillin, streptomycin and
tetracycline were 1 × 10-10, 1 × 10-9 and 1 × 10-9 g/mL, respectively. The detection time was 4 min, which was obviously better
than the requirement for the analysis of residual antibiotics at home and abroad. The electrode in 37 ℃ MRS medium could remain
stable for 7 days at least, and the low temperature preservation time was extended, suggesting that the electrode performance was
stable. In total, the microbial sensor by immobilized lactobacilli provides a new method for quantitative determination of antibiotics
with high sensitivity, low cost, simple operation and fast detection. Therefore, it is not only applicable to the quantification and
rapid detection of residual antibiotics in milk products, but also can detect a variety of types of antibiotics.

Key words: Lactobacillus helveticus, biosensor, penicillin, streptomycin, tetracycline