Cellular Damage in Dried Lactobacillus acidophilus

Lactobacillus acidophilus cells surviving freeze drying and vacuum drying became sensitive to oxgall and lysozyme probably from damage to the cell wall. The dried cells also became sensitive to NaCl and permeable to orthonitrophenol β-galactoside from damage to the cytoplasmic membrane. Scanning electron microscopy indicated loss of some surface material from the damaged cells. Transmission electron microscopy (TEM) revealed partial loss of wall and membrane material, but these losses seemed to have resulted from the treatments given during fixation of cells for TEM and as a consequence of damage to the wall and membrane that occurred during drying. A surface protein of 46-kilodalton molecular weight, that is bound to the wall by hydrogen bonding, was also lost from the dried cells. It is postulated that drying adversely affects some weak bonds of the cellular macromolecules probably from the loss of bound water.