Preservation of human gut microbiota inoculums for in vitro fermentations studies

Abstract:

The use of fecal inoculums for in vitro fermentation models requires a viable gut microbiota, capable of fermenting the unabsorbed nutrients. Fresh samples from human donors are used, however, the availability of fresh fecal inoculum and its inherent variability is often a problem. This study aimed to optimize a method to preserve pooled human fecal samples for in vitro fermentation studies. Different conditions and times of storage at -20ºC were tested.  In vitro fermentation experiments were carried out for both fresh and frozen inoculums and the metabolic profile compared. In comparison with the fresh, the inoculum frozen in a PBS and 30% glycerol solution, had a significant lower (p<0.05) bacterial count (<1 log CFU/mL). However, no significant differences (p<0.05) were found between the metabolic profiles after 48 h. Hence, a PBS and 30% glycerol solution can be used to maintain the gut microbiota viability during storage at -20°C for at least 3 months without interfering with the normal course of a colonic fermentation.

Keywords: gut microbiota viability, glycerol, human in vitro models, colon fermentation, organic acids, preservation