2.3. Assessment of phenotypic changes
2.3.1. Growth rate and yield studies
Cultures were grown overnight in each of the animal-free
media types and 2 μL of the overnight culture was added to
200 μL of medium in each well of a 96-well Microtest™ flat
bottom, polystyrene plate (Cat. No. 351172, Becton Dickinson).
The plate was incubated in a SpectraMax plate reader
(Molecular Devices, Sunnyvale, CA) at 30° or 37 °C depending
on the culture. The plate reader was set to shake the plate for
10 s every 20 min to provide increased aeration and cell dispersal.
The change in the optical density of each well was
measured at 600 nm with readings taken every 20 min. Logarithmic
growth rates for triplicate cultures were measured using
the equation ln(XT/X0)/ΔT where X is the absorbance at time T
during log phase and “final” OD600 values were determined as
the average value observed during stationary phase. The OD600
measurement of the plate reader was determined to be linear to
OD600=2.0.