Validation of growth as measurand for bacterial adhesion to food and feed ingredients

Aims: A miniaturized adhesion test was designed to study the binding capacity of food and feed ingredients for bacterial cells. Methods and Results: Bacteria were allowed to adhere to different fibrous materials supplied as well coatings in microtitration plates. The amount of bacteria retained on the materials was determined in an automated way as growth after addition of liquid medium. The test principle was based on an inverse relationship between initial cell densities and the appearance of growth: The higher adhering cell numbers are, the shorter are the detection times of growth. The growth curves obtained were fitted by nonlinear regression analysis employing a sigmoidal curve model. Growth parameters as (i) the time after incubation at which half of the maximum growth yield was reached; (ii) the time-coordinate of the point of inflection; (iii) the detection time calculated as x-axis intercept of the maximum specific growth rate in the point of inflection; and (iv) the time-coordinate of a growth detection threshold at OD = 0.05 were highly separating for the binding capacity of different food and feed ingredients for bacteria. Significance and Impact of the Study: With growth as measurand for adhesion, a simple, high-throughput method was developed for the screening of huge numbers of different binding matrices and bacteria.