2.2. Sample preparation
All four microalgae were harvested by centrifugation at 4000 rpm for 10 min; the resulting microalgal pellets were washed twice using either 0.5 mol L− 1 NH4HCO3 or distilled water for marine or fresh water species, respectively. The washed microalgal pellets were dried at 60 °C for 24 h to a consistent weight and then milled and sieved to obtain particles that were less than 200 μm in size. The samples were stored in a desiccator prior to testing.
2.3. Cell composition analysis
Total lipid content was determined using chloroform/methanol (v/v: 2/1) according to Bligh & Dyer [15]. Protein content was determined according to Rausch [16] and Bradford [17], and carbohydrate content was determined using sulfuric acid-anthrone according to Somani et al. [18]. The lipid, protein and carbohydrate content data were all collected in the lab.
2.4. Procedure and data analysis
TG experiments were carried out using a NETZSCH STA 449F3 under an air atmosphere at a gas flow rate of 100 mL/min. TG baselines were obtained by subtracting predetermined baselines obtained while performing the same procedure but without a sample. Approximately 10 mg of sample was placed in an Al2O3 ceramic crucible for each TG test. All tests were performed in triplicate. Variations in sample residual mass with respect to time and temperature change (TG data) were collected automatically. Peakfit software was used to analyze the TG and DTG curve data.