A combined pretreatment, fermentation and ethanol-assisted liquefaction process for production of biofuel from Chlorella sp. (1st December 2019)

• Record Type: Journal Article
• Authors: Rahman, Quazi Mahzabin; Zhang, Bo; Wang, Lijun; Shahbazi, Abolghasem
• Is Part Of: Fuel. Volume 257(2019)
• Publication Date: 2019-12-01
• Subjects: Microalgae -- Biodiesel -- Fermentation -- Ethanol-assisted liquefaction -- Biorefinery; Fuel -- Periodicals; Coal -- Periodicals; Coal; Fuel; Periodicals; 662.6
• DOI: 10.1016/j.fuel.2019.116026
• Languages: English
• ISSNs: 0016-2361

Abstract

Highlights: Chlorella processing includes pretreatment, fermentation and ethanol-assisted liquefaction. Glucose yield decreased by 25% when the biomass concentration increased from 100 to 150 g/L. Pichia obtained a higher ethanol yield (74.73%) than Saccharomyces (68.59%) at 100 g algae/L. Pretreatment and fermentation increased microalgal lipid content from 8.2% to 12% Pretreatment and fermentation before liquefaction increased the crude biodiesel yield by 40.7% Abstract: A combined pretreatment, fermentation and ethanol-assisted liquefaction approach was investigated to produce biofuel and biochemicals from freshwater microalga Chlorella sp. Microalgal biomass was pretreated with dilute sulfuric acid in different acid concentration (1–3 wt.%), biomass concentration (40–150 g/L) and pretreatment time (15–60 mins) to observe the effects on carbohydrate yield. The glucose concentration of 10.88 g/L was obtained with a glucose yield of 90.7% from biomass loading of 80 g/L pretreated with 3% (wt%) dilute sulfuric acid at 121 °C for 60 min. The usability of the pretreated hydrolysate as fermentation medium was determined using two yeast species– Saccharomyces cerevisiae and Pichia stipitis . Similar ethanol yields were obtained from both yeasts at lower biomass loading of 40 g/L. However, at increased biomass loading of 100 g/L, P. stipitis obtained higher ethanol yield of 74.73% with higher glucose and xylose utilization compared to ethanol yield of 68.59% from S. cerevisiae . Following fermentation, liquefaction assisted with 15% (v/v) ethanol at 265 °C converted fermented microalgae to crude biodiesel, aqueous products and solid residue. This newly developed process could increase the crude biodiesel yield by 40.7%, compared to liquefaction of original microalgae. The main advantage of this combined approach is the utilization of fermented algae in essential ethanol production within the process to enhance the crude biodiesel yield by ethanol-assisted liquefaction.