Designing and optimizing of cryoprotective culture based on nanocellulose to enhance the viability of Lactobacillus Brevis JN368471.1 during freeze drying

Freeze drying in particular is the preferred method for transporting and storing vast culture collections of micro-organism strain types. The main disadvantage of this method is cell damage induced through freezing. The usage of cryoprotectants due to the formation of glassy state would decrease cell damages through this stage. In this study, optimization of freezing media containing protective agents of nanocellulose, skim milk and trehalose was done using statistical design of response surface methodology (Central Composite Design). To determine the size of nanocellulose particles produced from cotton linter, atomic force microscopy and scanning electron microscopy were used. Nanocellulose particles had a width of less than 50 nm and length of hundreds of nanometers to several micrometers. Indigenous Lactobacillus brevis isolated from traditional dairy products were selected as target cells. By solving the regression equation, and analyzing the response surface plots, the optimal concentrations of the agents to maximize cell viability were determined as: Nanocellulose 13.75%, trehalose 20.5% and skim milk 13.75%. It seems thatnanocellulose can be adsorbed on the surface of micro-organisms and form a viscous layer, preventing the growth of ice crystals by increasing the viscosity of the solution, and also keeps glass structure of ice near the cells. The results showed that RSM could effectively assess the main and interaction effects of protective factors on cell viability.