Freeze-Drying of Lactic Acid Bacteria: A Stepwise Approach for Developing a Freeze-Drying Protocol Based on Physical Properties

Abstract

Freeze-drying or lyophilization has become a reference process for preserving lactic acid bacteria. The development of stable freeze-dried lactic acid bacteria (LAB) requires maintaining the biological activity of the cells and the macroscopic porous structure while increasing the efficiency of the manufacturing process. Physical properties of protective solutions such as glass transition and collapse temperature, are key elements not only for process optimization but also for the stability of freeze-dried LAB. This chapter provides a stepwise approach for developing a protective formulation for long term preservation of LAB and an efficient freeze-drying process. Methods for determining glass transition and collapse temperatures of protective solutions and cell suspensions, as well as water activity and water content of freeze-dried products are described.

Ligilactobacillus salivarius functionalities, applications, and manufacturing challenges

“…The addition of a washing step to remove the residual fermentation metabolites such as lactic acid is sometimes necessary to make possible the drying process or improve its productivity (Fonseca et al 2004;Fonseca et al 2021).…”

“…Freeze-drying is a technique that comprises three steps that operate at different temperatures and pressures. It involves freezing of the aqueous solution containing bacteria, followed by primary drying to sublimate ice to water vapor and, finally, secondary drying to remove unfrozen water by desorption (Muller et al 2009;Fonseca et al 2015;Fonseca et al 2021). The final product is a dry cake that requires a further grinding step to obtain individual particles.…”

“…Among glassy forming molecules, polymers such as maltodextrins are very interesting protective agents because they ensure physical stability and increases the efficiency of the manufacturing process (Fonseca et al 2021). They exhibit high glass transition temperatures (Tg) in the liquid (Fonseca et al 2021) and dry states (Roos and Karel 1991). Maltodextrins, therefore, provide a glassy stable matrix over a wide range of temperatures in the frozen and dried states.…”

“…acidic conditions, heat-shock) (Huang et al 2017). Furthermore, protective molecules and particularly sugars are added to the concentrated culture before stabilization (Teng et al 2017;Broeckx et al 2017;Archacka 2019;Broeckx et al 2019;Fonseca et al 2021).…”

Protective effects of whey protein hydrolysate on Bifidobacterium animalis ssp. lactis Probio-M8 during freeze-drying and storage

“…Maintaining the quality of lactic acid bacteria in products during freeze-drying and storage depends on the lyoprotectant and the drying and storage conditions (Aragón-Rojas et al, 2020;Fonseca et al, 2021). When used as a lyoprotectant in freeze-dried B. lactis Probio-M8, the acidic nature of whey protein hydrolysate may have altered the expressions of genes and proteins related to fatty acid synthesis, thereby improving survival during freeze-drying (E et al, 2021).…”