Improving total glutathione and trehalose contents in Saccharomyces cerevisiae cells to enhance their resistance to fluidized bed drying
Résumé
Fluidized bed drying is a dehydration process often applied to microorganisms and used for food particles stabilization. Despite its common use in yeast production, this process can lead to cell death depending on the strain and the growth conditions. During fermentation, yeasts undergo nutritional stressful environments according to media composition. In order to face these conditions, yeasts are able to synthesize protective molecules, e.g. glutathione (tripeptide, an antioxidant) and trehalose (disaccharide, a cell desiccation protector). However, the role of these two molecules during fluidized bed drying is still not well known. This work aimed to investigate if total glutathione (GSHt) and trehalose (TRE) accumulation leads to the creation of more resistant and stable yeast cells. The effect of GSHt accumulation after relatively nutrient richer cultivation on cell resistance to mild stress (45 degrees C-90 min) was obvious. This growing condition also improved the stabilization and performance of cells after rehydration. On the other hand, the highest amount of TRE stored by yeasts cultivated in nutrient poorer media led to cells being more resistant to severe stress (60 degrees C-60 min). This strategy could be used for the development of new bioprocesses focusing on improving the performance and resistance of cells after fluidized bed drying.