Porous PEG Scaffold Fabricated via Emulsion-Templating Technique Towards Immobilization of Saccharomyces cerevisiae Cells

The cell immobilization technique, which restricts living cells to a certain space, has received widespread attention as an emerging biotechnology. In this study, a yeast (Saccharomyces cerevisiae)-loaded highly open-cell emulsion-templated polyethylene glycol (PEG-polyHIPE) was synthesized to be a reusable enzymatic catalyst. An emulsion was prepared with polyethylene glycol diacrylate (PEGDA) aqueous solution, cyclohexane, and polyethylene-polypropylene glycol (F127) as the continuous phase, dispersed phase, and surfactant, respectively. Then PEG-polyHIPE was obtained by polymerization of the PEGDA in emulsion. The highly porous materials obtained by the emulsion-templating method are suitable for use as carrier materials for yeast immobilization, due to their favorable structural designability. During the activation process, the yeast S. cerevisiae can readily gain access to the interior of the material via the interconnected pores and immobilize itself inside the voids. The yeast-loaded polyHIPE was then used to ferment glucose for ethanol production. The yeast immobilized inside the polyHIPE has high fermentation efficiency, good recoverability, and storage stability. After seven cycles, the yeast maintained 70% initial fermentation efficiency. The S. cerevisiae kept more than 90% of the initial cellular activity after one week of storage both in the dry state and in yeast extract peptone dextrose medium (YPD) at 4 °C. This study strongly demonstrates the feasibility of using high-throughput porous materials as cell immobilization carriers to efficiently osmotically immobilize cells in polyHIPEs for high-performance fermentation.