Preservation of Human Gut Microbiota Inoculums for In Vitro Fermentations Studies

• Published in: Fermentation (Basel) Vol. 7; no. 1; p. 14
• Main Authors: de Carvalho, Nelson Mota, Oliveira, Diana Luazi, Dib Saleh, Mayra Anton, Pintado, Manuela, Madureira, Ana Raquel
• Format: Journal Article
• Language: English
• Published: MDPI AG 2021
• Subjects: colon fermentation; glycerol; gut microbiota viability; human in vitro models; organic acids; preservation
• ISSN: 2311-5637; 2311-5637
• DOI: 10.3390/fermentation7010014

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 of preserving pooled human fecal samples for in vitro fermentation studies. Different conditions and times of storage at −20 °C 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 significantly 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 colonic fermentation.