Green biorefinery of fresh cattail for microalgal culture and ethanol production.

Green biorefinery represents an appropriate approach to utilize the fresh aquatic biomass, eliminating the drying process of conventional bioenergy-converting system. In this study, fresh cattails were homogenized and then filtered, whereby cattails were separated into a fiber-rich cake and a nutrient-rich juice. The juice was used to cultivate microalgae Chlorella spp. in different media. In addition, the solid cake was pretreated with the sonication, and used as the feedstock for ethanol production. The results showed that the cattail juice could be a highly nutritious source for microalgae that are a promising feedstock for biofuels. Sugars released from the cattail cake were efficiently fermented to ethanol using Escherichia coli KO11, with 8.6-12.3% of the theoretical yield. The ultrasonic pretreatment was not sufficient for pretreating cattails. If a dilute acid pretreatment was applied, the conversion ratio of sugars from cattails has the potential to be over 85% of the theoretical value.