Microfluidic alginate encapsulation for stabilization of carotenoid-rich microalgal biomass of Chromochloris zofingiensis.

Carotenoids have considerable value because of their strong antioxidant activity; however, their practical applications are limited by their low stability under light exposure. In this study, a microfluidic flow-focusing technique was employed to encapsulate intact Chromochloris zofingiensis cells within alginate microcapsules to enhance the photostability of intracellular carotenoids. Microcapsules were produced using aqueous sodium alginate solutions containing microalgae, which were dispersed into mineral oil containing Span 80, followed by ionic gelation in calcium chloride solution. The effects of alginate concentration (1.5 to 3.5% w/v) and microcapsule size (119 to 201 µm) on carotenoid stability under intense light exposure (40000 lx for 20 days) were investigated. Encapsulation considerably improved carotenoid stability, increasing the percentage of remaining carotenoid (PRM) from 3.09% for free cells to 48.70% for cells encapsulated in 1.5% alginate. Further increase in the alginate concentration to 3.5% led to improvement in PRM to 62.1%. Microcapsule size had a greater influence on carotenoid stability than alginate concentration. Increasing the microcapsule size from 119 to 201 µm improved PRM from 40.3% to 70.4% due to reduced light penetration. The results revealed that microcapsule size itself was significantly influenced by alginate and microalgae concentrations, and flow rate. This study demonstrates that encapsulation of intact microalgal cells is an effective strategy for stabilizing intracellular carotenoids and provides insights into the design of protective encapsulation systems for carotenoid-rich biomass.