Characterization of encapsulated riboflavin in plasmolyzed and non-plasmolyzed Saccharomyces cerevisiae yeast cells.

Riboflavin (RF) or vitamin B₂ is susceptible to photodegradation. Encapsulation of sensitive components by modified yeast cells is a promising method for their widespread usage at industrial scale. Saccharomyces cerevisiae has been introduced as an appropriate carrier of bioactive compounds. The yeast cell comprises a phospholipid membrane that protects the core from the external environment. In this study, the effect of plasmolysis on efficiency of S. cerevisiae cells in encapsulation of RF were investigated. According to the results, plasmolysis increased the encapsulation efficiency (53.85% versus 58.22% for non-plasmolyzed and plasmolyzed yeast cells, respectively) and loading capacity (14.10 and 16.99% for non-plasmolyzed and plasmolyzed yeast cells, respectively). The loaded intact cells had a tied and intertwined structure while the loaded plasmolyzed cells were seen separately in the Scanning Electron Microscope images. According to the Transmission Electron Microscope images, plasmolysis did not destruct the yeast cells and the cell integrity was retained appropriately after the process but it increased the internal space for encapsulation. In X-ray diffraction analysis, RF had a crystalline structure and its encapsulation within the amorphous non-plasmolyzed and plasmolyzed yeast cells led to slight crystallinity in the structure of complex. The observed spectra of functional groups in Fourier Transform Infrared spectroscopy confirmed the successful entrapment of RF in the yeast cells. Plasmolysis depleted the cell contents susceptible to thermal process through which melting point of the yeast cells increased. Owing to the charged surface of yeast cells, they showed a burst release of RF in the simulated stomach (88% for non-plasmolyzed and 84% for plasmolyzed cells) and intestinal fluid (91% and 96% for non-plasmolyzed and plasmolyzed cells, respectively). [ABSTRACT FROM AUTHOR]