Optimization of Lactobacillus rhamnosus viability during freeze-drying by box-behnken design
Abstract
Freeze drying is the most extensively used preparation and preservation technology for the cells. However, the freeze-dried cells may be injured during this process and can cause significant cell death. In this work, we aimed to optimize hydroxyproline, sucrose and isomaltooligosaccharide concentrations in order to maximize the survival rate of Lactobacillus rhamnosus during freeze drying, using response surface methodology (RSM). A Box-Behnken design was used to evaluate the effects of these cryoprotectants on the Lactobacillus rhamnosus cells in terms of viability. The optimal concentrations of the added compounds in the medium were experimentally studied and they were found to be (w/w): 12.11 % for hydroxyproline, 9.67 % for sucrose and 2.56 % for isomaltooligosaccharide. When Lactobacillus rhamnosus cells were dried by using the cryoprotectants found in the optimum concentration, a rate of 67.78±0.26 % cells survived and the cell viability reached the value of 1.79±0.05×1011 CFU/g.
