2.3. Preparation of Gelatin-GO Hydrogels

Sterile milli-Q water was heated up to 40 °C and mixed with gelatin Type A (food grade). The mixture was kept under mechanical stirring at 180 RPM for 30 min. GO solution (1.0 mg/mL) was added at 40 °C and 180 RPM for an additional 5 min. Glutaraldehyde (GTA) solution 25% (v/v) for crosslinking (PanReac AppliChem, Barcelona, Spain) was added dropwise while stirring at 80 RPM in a water bath at 40 °C for 1 h. Simultaneously, the yeast cells were resuspended in sterile water and carefully poured into the hydrogel solution to reach a final 5.0% (w/v) concentration. The mixture was cooled down to room temperature and poured into silicone molds food grade (La Orquidea, semi-sphere, Colombia). Finally, the obtained hydrogels were stored at 4 °C until further use. The complete procedure was completed in a laminar flow hood using sterilized materials and equipment (Figure 1).