Abstract
In the present paper, the Layer by Layer (LbL) method using β-lactoglobulin and sodium alginate was performed to individually encapsulate Saccharomyces cerevisiae cells in microorganized shells in order to protect them against stresses during dehydration. Higher survival (∼1 log) for encapsulated yeast cells was effectively observed after air dehydration at 45°C. For the first time, the potentiality of Synchrotron-Fourier Transform InfraRed microspectroscopy (S-FTIR) was used at the single-cell level in order to analyze the contribution of the biochemical composition of non-encapsulated vs. encapsulated cells in response to dehydration. The microspectroscopy measurements clearly differentiated between non-encapsulated and encapsulated yeast cells in the amide band region. In the spectral region specific to lipids, the S-FTIR results indicated probably the decrease in membrane fluidity of yeast after dehydration without significant distinction between the two samples. These data suggested minor apparent chemical changes in cell attributable to the LbL system upon dehydration. More insights are expected regarding the lower mortality among encapsulated cells. Indeed the hypothesis that the biopolymeric layers could induce less damage in cell by affecting the transfer kinetics during dehydration-rehydration cycle, should be verified in further work.
Highlights
Saccharomyces cerevisiae is an eukaryotic model organism widely used in many technological applications in food industries and in biofuel production
Before dehydration at 45◦C, no significant differences (p < 0.05) in the logarithm of Colony-Forming Unit (CFU) per mL between encapsulated and non-encapsulated cells indicated that encapsulation conditions did not affect yeast cultivability
Authors have previously demonstrated that S. cerevisiae cells preserved their metabolic activities and were able to divide after encapsulation process using Layer by Layer (LbL) method (Diaspro et al, 2002; Drachuk et al, 2012)
Summary
Saccharomyces cerevisiae is an eukaryotic model organism widely used in many technological applications in food industries and in biofuel production. The main method used to preserve yeast is dehydration During this process, cells are subjected to several stresses such as mechanical, hydric, thermal and oxidative stresses, and inducing cell death (Beker and Rapoport, 1987; Fu and Chen, 2011). Dehydration in aerobic conditions increases the contact between cell surfaces and air, inducing the accumulation of reactive oxygen species (Gamero-Sandemetrio et al, 2014). Another previous works have shown that cell oxidation level increased significantly during airdrying (Pereira de Jusus et al, 2003; Garre et al, 2010). Oxidation phenomena cause damage to cell proteins, lipids, and nucleic acids (França et al, 2007) with severe consequences on the overall metabolism (Hansen et al, 2006)
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