Evaluation of the Potential of Chlorella vulgaris for Bioethanol Production

For bioethanol to be a sustainable transportation fuel, appropriate feedstock needs to be established. The focus of the current work is to evaluate if the microalga Chlorella vulgaris could be the feedstock of choice. Exclusive formation of glucose was observed upon the acid (HCl) hydrolysis of C. vulgaris. Microwave irradiation as well as hydrothermal reaction were employed as heating methods. Under optimal hydrolysis conditions using microwave irradiation (100 °C, 1 M HCl, and 10 min), the glucose yield was 20 ± 3.5 wt % compared to 23 ± 4 wt % under the optimal hydrothermal reaction conditions (120 °C, 1 M HCl, and 60 min). The hydrothermal-based hydrolysis process was further scaled up from a 0.2 g batch to a 2.0 g batch, and the glucose obtained was converted to bioethanol in a fermentation process at 30 °C for 28 h using Saccharomyces cerevisiae. An ethanol yield as high as 13.2 ± 0.5 wt % was obtained from C. vulgaris.