Robust experimental design for optimizing the microbial inhibitor test for penicillin detection in milk

Area of Science:

• Microbiology
• Analytical Chemistry
• Food Safety

Background:

• Penicillin G residues in milk pose a public health risk.
• Accurate detection methods are crucial for ensuring milk safety and compliance with Maximum Residue Limits (MRLs).

Purpose of the Study:

• To optimize a microbiological inhibition test for Penicillin G detection in milk using experimental design.
• To develop a dichotomous response assay with enhanced sensitivity and reliability.

Main Methods:

• Employed a 2(3) x 2(2) robust experimental design with two replications.
• Investigated control factors (culture medium volume, spore concentration, indicator concentration) and noise factors (diffusion time, incubation period).
• Utilized a multiple logistic regression model for data analysis.

Main Results:

• Identified significant effects of culture medium volume, spore concentration, diffusion time, and incubation period.
• Optimized parameters include 100 µL culture medium, 2 x 10^5 spores/mL, 60 min diffusion, and 3 h incubation.
• Achieved a Penicillin G detection limit of 3.9 µg/L, aligning with MRLs.

Conclusions:

• The optimized bioassay effectively detects Penicillin G at MRL levels.
• Experimental design and logistic regression successfully optimized dichotomous response bioassays.
• This method aids in preventing consumer health issues related to antibiotic residues.