A microplate bioassay to determine ε-polylysine based on antimicrobial activity

Abstract:

Based on the antimicrobial activity of ε-Polylysine, a 96-well microplate bioassay was established to rapidly determine large numbers of ε-Polylysine samples. The results showed that a high correlation coefficient (R2=0.997 5) was obtained for linear regression in the ε-polylysine concentration range of 100.00?500.00 mg/L with 107?108 CFU/mL indicator strain (Micrococcus luteus) and the incubation time of 4 h. Using these parameters, the microplate bioassay has showed good precision and accuracy, and the relative standard derivation (RSD) and relative derivation (RD) were lower than 3.5% and 3.0% respectively. Compared with the results by Itzhaki method and HPLC assay, the microplate bioassay shows no considerable difference with HPLC, but can directly indicate the inhibition activity and more suitable for rapid determination of numerous samples, which can be used for ε-polylysine quantification in fermentation process and high throughput screening from large numbers of mutants.

Key words:ε-polylysine, Microplate, Bioassay, Inhibition activity, Micrococcus luteus