Enhancement of continuous fermentative bioethanol production using combined treatment of mixed microalgal biomass

The impact of combined sonication, heat and enzyme (SHE) treatment on continuous bioethanol production from mixed microalgal biomass (cyclotella and filamentous) was evaluated in a fermentor. Different pretreatments resulted in varied degrees of cell lysis for microbial fermentation. Filamentous algae were partially damaged under sonication pretreatment, while SHE treatment leads to complete destruction of both cyclotella and filamentous microalgal cells. SHE treatment significantly increased the dissolved carbohydrate concentration (up to 5.8 folds greater than non-pretreated), which enhanced the ethanol production through microbial fermentation. Higher bioactivity of alcohol fermentation by Dekkera bruxellensis (yeast) resulted in higher ethanol yield compared to mixed bacterial culture. The cumulative ethanol production after SHE treatment was 1.4 fold higher than with combined sonication and enzyme (SE) treatment using D. bruxellensis. These results demonstrate that combined SHE treatment is an effective method for the enhancement of yeast promoted fermentative bioethanol production from mixed microalgal biomass.