Vacuum facilitated infusion of bioactives into yeast microcarriers: Evaluation of a novel encapsulation approach

Encapsulation into yeast microcarriers provides an appealing alternative to biomimetic systems by employing natural, pre-formed vehicles for the stabilization and delivery of bioactives compounds. However, current (diffusion-limited) methods of encapsulation using yeast require long time scales and heating which lead to poor encapsulation efficiencies and yields. This study evaluates the usage of vacuum infusion to encapsulate two model bioactivesi curcumin and fisetin, into yeast and yeast cell wall particles and the physical parameters, e.g. vacuum level, concentration of carrier solvent, log p value of bioactive, etc., which facilitate the process of vacuum infusion. Encapsulation efficiencies were determined using UV-vis spectrophotometry. Localization of bioactives within yeast microcarriers was determined using confocal and multiphoton (two-photon) microscopy. 99% vacuum, or 1.0 kPa, and 35% ethanol (v/v) provide the optimal conditions for the encapsulation of both curcumin and fisetin; Compared to the diffusion-limited method, vacuum infusion is able to encapsulate 3 x more curcumin and 2 x more fisetin into yeast microcarrier and requires 288-fold less time. Enhanced encapsulation efficiencies and yield as well as rapid encapsulation process technology presented in this study can transform the use of cell based carriers for encapsulation and delivery of bioactives.