Microalgae, as photosynthetic microorganisms, contain a rich composition of bioactive compounds such as proteins, lipids, carbohydrates, vitamins, an‎d antioxidants. These characteristics have led to the remarkable expansion of microalgae applications in various industries. However, the sensitivity of microalgal cells to environmental factors such as temperature, pH, an‎d intense light creates significant challenges in maintaining their viability an‎d biological activity in industrial processes an‎d end-use applications. To address these challenges, microencapsulation has been considered an effective solution. Moreover, microfluidic technology, due to its unique capabilities, provides an efficient approach for performing microencapsulation processes. These advantages lead to improved encapsulation efficiency, reduced raw material consumption, an‎d the production of microcapsules with narrow size distribution an‎d high stability. The aim of this study was the microencapsulation of microalgal cells within alginate microcapsules using microfluidic technology in order to preserve their properties. An aqueous sodium alginate solution containing microalgae (aqueous phase) was injected into a hydro‎phobic-walled flow-focusing microfluidic chip, where it came into contact with mineral oil containing the surfactant Span-80 (oil phase). This resulted in the formation of alginate microdro‎plets carrying microalgae inside the chip. The biphasic fluid exiting the chip was collected in a container filled with aqueous calcium chloride solution, during which the alginate gelled upon contact with calcium chloride an‎d microcapsules were formed. The size of the microcapsules in this study ranged from 97 to 205 µm. The results showed that the flow rates of the phases, the volumetric flow rate ratio of the phases, an‎d the alginate concentration had a significant effect on the microcapsule size. In addition, the concentration of microalgae also had a meaningful effect on microcapsule size, although its influence was weaker compared to the three aforementioned parameters. To eva‎luate the stability of encapsulated microalgae, aqueous phases with a microalgal concentration of 8 × 10^6 cells/ml an‎d different alginate concentrations were used. Free an‎d encapsulated microalgal cells were exposed to intense light (40,000 lux) for 20 days. Measurements of total carotenoids an‎d microscopic imaging showed that at alginate concentrations of 1.5% (wt/v) an‎d 2.5% (wt/v), 48,69% an‎d 59.38% of the carotenoids of encapsulated microalgae were preserved, respectively, while free microalgae lost nearly all their carotenoids an‎d became decolorized. The findings of this study not only emphasize the great potential of microfluidic technology in the development of microalgae encapsulation systems, but also demonstrate that encapsulating microalgae in alginate can significantly contribute to the preservation of their valuable compounds.

محمد هادي جزيني , مهدي ستاري نجف آبادي

حميد زيلوئي , نسرين اعتصامي