The effect of inoculum age and solid versus liquid propagation on inoculum quality of an industrial Bacillus licheniformis strain.

Shorter lag phases were obtained in cultivations of Bacillus licheniformis using early-compared to late-stationary growth phase inocula and using liquid versus solid propagation medium. Flow cytometry and fluorescence ratio imaging microscopy (FRIM) after staining with 5(6)-carboxyfluorescein diacetate succinimidyl ester (CFDA-SE), confirmed that liquid early-stationary growth phase inoculum had a higher vitality and was more homogeneous than solid late-stationary growth phase inoculum. DNA-microarray analyses indicated that liquid early-stationary growth phase inoculum was in a more active state in terms of cell multiplication whereas solid late-stationary growth phase inoculum was induced to some spore formation potentially causing delayed growth initiation.