9. Thermal analysis of immobilized yeast by differential scanning calorimetric (DSC) and thermogravimetric assays (TGA)
A differential scanning calorimeter equipped with a cooling device (Netzsch DSC-204-F1-Phoenix), was used to measure the phase transition of water adsorbed on the polymer samples: pAAm-Sc-4 and pAAm, under high purity N2 flow. All the samples were previously swollen in distilled water until swelling equilibrium state was reached. The DSC curves were obtained by sample cooling (10 °C/min) from room temperature to −30 °C using liquid N2, followed by a reheating at a scanning rate of 10 °C/min until reach 25 °C. The measurement was repeated five times with the same protocol to check the reproducibility. The experimental error of these measurements was ±150 J/g and ±2 °C in temperature measurement. The thermogravimetric measurements were carried out in a thermogravimetric device, Netzsch TG-209-F1-Libra. The equipment was use to analyze temperature tolerance of polymer samples: pAAm-Sc-4 and pAAm as a comparative system. The following operating conditions were chosen: 10 mg of the dry hydrogel, heated from 50 °C to 300 °C, at 5 °C/min rate under flowing (200 ml/min) high purity nitrogen. Each sample was analyzed three times, and the average value was informed. The experimental error of these measurements was for all studied samples of ±0.5% in weight loss measurement and ±2 °C in temperature measurement.