Harnessing Ulva ohnoi for eco-friendly bioethanol production via hydrothermal pretreatment

Background: The increasing demand for renewable energy sources has sparked interest in biofuels derived from green seaweeds, owing to their abundance and high carbohydrate content. Ulva ohnoi, harvested from Taiwan's shores, presents a promising candidate for bioethanol production due to its favorable characteristics. Methods: In this study, Ulva ohnoi underwent hydrothermal pretreatment at temperatures of 120 degrees C, 150 degrees C, and 180 degrees C for 20 min. The pretreated slurry obtained at 180 degrees C was subjected to enzymatic saccharification at pH 4.8 and 50 degrees C for 72 h. This process resulted in the production of 5.8 g/L of glucose, which was subsequently concentrated to 18.86 g/L. Significant Findings: Fermentation of the concentrated sugar fractions using Saccharomyces cerevisiae WLP 300 at 30 degrees C for 24 h yielded remarkable ethanol yields of 0.39 and 0.43 g/g of sugar. These yields approached the maximum theoretical values of 76.1% and 84.58%, respectively. Additionally, the study reported a maximum ethanol productivity of 0.54 g/L/h in the 12th hour in the concentrated fraction. These findings underscore the potential of Ulva ohnoi as a sustainable biofuel and clean energy source, aligning with Sustainable Development Goal 7 (SDG 7) of ensuring access to affordable, reliable, sustainable, and modern energy for mankind.