Rational fabrication of count film for coliform hypersensitive enumeration based on enzyme-response compound color rendering

Abstract

A sensitive and portable count film based on dedicated enzyme response combined with a composite chromogenic agent was fabricated for coliform enumeration. Cold-water gel was conjugated with 5-bromo-4-chloro-3-indolyl-β-d-galactoside, crystalline violet, neutral red, and lactose to prepare a composite chromogenic agent. The involvement of MgCl2 and isopropyl-β-D-thiogalactoside appreciably boosted the analytical performance. Compounding with Tween-80 and porous starch, stable bubbles provided corroborative evidence for positive colonies without any further validation. The proposed count film exhibited prominent enumeration performances within the linear range of the relationship varied from 3 CFU/mL to 150 CFU/mL, with an LOD of 3 CFU/mL. The as-obtained coefficient of variation was less than 5%, and recovery rates ranged from 101.30% to 104.47%. In light of its favorable sensitivity and satisfactory feasibility, this reliable analytical pattern provided a novel potential orientation for the evaluation of microorganisms in food-safety detection.