Ethanol Production from Ulva fasciata

Abstract

The theoretical potential yield of Ulva fasciata as a biomass feedstock for fermentative ethanol was found to be about 310 L per tonne, dry weight. U. fasciata has numerous characteristics that render it a suitable mariculture energy crop. Specifically, it forms large complex structures that grow quickly, with high (14%) dry to wet weight percentages, holocellulose content for the dry mass of 51%, carbohydrate content of 5%, and relatively low (5%) lignin content. Enzymatic saccharification with a commercial cellulase (Accelerase) from Genencor was investigated: After a 12 hr digestion, 25% of the potential glucose was recovered from the cellulose fraction. The hydrolysate was supplemented with a modified YM medium and used directly for batch fermentation. A 12 hr incubation resulted in complete utilization of the glucose and production of ethanol. In this preliminary investigation, the ethanol yield corresponded to approximately 126 L per tonne (dry weight) of macroalga, or ～43% of the theoretical alcohol yield with respect to only the cellulose and carbohydrate contents. Theoretical yields are higher when the hemicellulose fraction is considered. While sugar recovery needs further optimization, the data suggest that additional work is warranted.