Improving diffusivity of encapsulated Saccharomyces cerevisiae via porous silica-alginate for enhanced bioethanol production

Bioethanol production was enhanced through porous silica-alginate/chitosan encapsulation of Saccharomyces cerevisiae in the fermentation process. Glucose was used as a pore-forming agent (PFA) during the silica coating process, with the PFA concentration values of 0 (G-0), 0.75 (G-0.75), 1.5 (G-1.5), and 3 g (G-3). The diffusion coefficient for G-3 was approximately 2.32 cm³ /s, representing an increase of 3.2 times compared to the reference G-0. The bioethanol production significantly increased from G-0 (2.73 ± 0.14 g/L) to G-3 (4.50 ± 0.24 g/L), indicating a 1.7-fold improvement attributed to enhanced membrane diffusivity. Optimal conditions for bioethanol production were determined as 35$℃$, pH 5, and 150 rpm using 30 capsules for 10 g/L glucose. Capsule reusability revealed that G-0 and G-0.75 endured nine cycles, while G-1.5 and G-3 exhibited signs of failure after seven cycles, revealing a delicate balance in enhanced porosity and capsule stability. This result holds promise for alleviating the mass transfer limitations associated with traditional silica-coated/chitosan capsules in bioethanol production.