Microencapsulation of microbial cells is an attractive method for many applications.
Controlled aggregation can protect cells from environmental inhibitors, increase the
productivity of the process, facilitate the reuse of cells, or ensure the protection and
release of cells under desired conditions. In this master's thesis, we studied the
polysaccharide coacervation method for simultaneous aggregation of Saccharomyces
cerevisiae yeast cells. We chose chitosan as the main carrier polymer, and in
combination with chitosan we also tested additional components: (i) cyclodextrins (CD)
– α, β, γ, and/or (ii) alginate in different concentrations. We observed the formation of
aggregate size over time and the percentage of cells that were entrapped in aggregates
or that remained free. We concluded that the different tested CDs did not significantly
affect the aggregation and particle size, while different concentrations of alginate
significantly affected the obtained aggregates. Aggregates between 50 and 100 μm in
size were formed in all samples, with the exception of the sample containing chitosan
(1 mg/mL) and alginate (1 mg/mL), where aggregates larger than 1 mm were formed.
The highest percentage of cells (60.7%) was captured in aggregates with chitosan (1
mg/mL) and alginate (0.5 mg/mL), and the lowest (25.4 %) in the sample with chitosan
(1 mg/mL) and alginate (0.25 mg/mL). Among the CDs, γ-CD performed best (56.8%)
in the success of binding cells into aggregates, while the values in the presence of α-CD
(40.8%) and β-CD (43.6%) were slightly lower. In the thesis, we also monitored the
viability of cells entrapped in aggregates. After 24 hours the percentage of viable cells
was between 77.5% and 92.9% for all samples. The developed method for the controlled
aggregation of S. cerevisiae is simple, fast and, at the same time, does not require
expensive machines or technically demanding implementation, and as such is also
suitable for implementation in aseptic conditions.
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