A combined pretreatment, fermentation and ethanol-assisted liquefaction process for production of biofuel from Chlorella sp.

[摘要] 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 degrees 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 degrees 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.

[发布日期] 2019-12-01

[关键词] Microalgae;Biodiesel;Fermentation;Ethanol-assisted liquefaction;Biorefinery