Date of Award
Master of Science (MS)
A key focus of microalgae-based fuels/chemicals research and development has been on the lipids that many strains generate, but recent studies show that solely recovering these lipids may not be cost competitive with fossil-derived processes. However, if the carbohydrates can also be recovered and ultimately converted into useful chemical intermediates, this may improve the economics for microalgae-based sustainable product technologies.
In the present work, physical and chemical pre-treatments were performed on the Chlorella vulgaris microalgae strain to recover the carbohydrates from the biomass. A central composite design approach was used to optimize hydrolysis conditions including temperature, acid concentration, microalgae solid-to-liquid loading, and hydrolysis time. Results showed that the highest recovery of total carbohydrates obtained was 90 ± 1.1 wt% at 95% confidence with hydrolysis of 20 mL/g of ball-milled biomass performed in an autoclave at 120 °C using 4 wt% sulfuric acid for 30 minutes. This represents a recovery of 40 wt% of the initial biomass weight. Sequential recovery of carbohydrates and lipids was also explored. Lipid recovery was maximized with pure methanol as a solvent, at a solid-to-liquid loading of 10 mL/gbiomass, at a temperature of 180 °C for 20 minutes in an autoclave. The highest recovery of total lipids was 71 ± 1.8 wt%, which represents 22 ± 0.9 wt% of the initial biomass weight. The sequential extraction of carbohydrates followed by lipids resulted in recovery of 60 ± 1.6 wt% of the initial biomass weight with 90% recovery of carbohydrates and 59% recovery of lipids. Even though the recovery of total lipids was reduced, around 60 wt% of the biomass was made available for further transformations into fuels or other higher value chemicals, which is higher than current single product recovery strategies.
Hammann, William Richard, "Method Development And Optimization For The Recovery Of Carbohydrates From A Microalga Species Of Chlorella Vulgaris By Combined Physical And Chemical Pre-Treatments" (2019). Theses and Dissertations. 2559.