Strategies to improve carotene entry into cells of Yarrowia lipolytica in a goal of encapsulation

Yeasts are good materials for encapsulation of actives, but, as they are preformed capsules, they have to be loaded. Our goal was to load cells with a big and very hydrophobic molecule, β-carotene (LogP ≈15). In classical conditions, the entry of this compound into cells is negligible and we have worked on ways to favor the entry through the cell wall. Carotene was prepared at 0.3-3 g L−1 in solvents to improve solubility and alter the cell wall structure. After a 3 h-incubation of cells with this solution, with the apolar hexane, the entry was increased to 95 μg g−1 cell wet weight but the monopolar chloroform was much more efficient (220 μg g−1 cell wet weight). However, increasing the carotene concentration in chloroform increased the adhesion of carotene on the cell wall (over 900 μg g−1 cell wet weight) but did not increase the amount into the cell. The use of ultrasound (6-min-treatment at 50% and an output control of 4) as a green physical treatment increased significantly the result for β-carotene encapsulation (852 μg g−1 cell wet weight).