Date of Award

January 2019

Document Type


Degree Name

Master of Science (MS)


Chemical Engineering

First Advisor

Wayne Seames


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.