Effect of enzymatic saccharification on edible seaweed (Ulva sp.) fermentation

Edible seaweeds are a promising substrate for microbial fermentations and the development of novel food products; however, the unique composition of their cell wall can limit microbial growth. To address this, the edible seaweed Ulva sp. was subjected to enzymatic saccharification using: i) a crude extract of Aspergillus oryzae grown on Ulva sp.; ii) a commercial enzymatic cocktail; and iii) a combination of both. A response surface methodology (RSM) optimization was applied using a three-factor Box-Behnken design to identify optimal saccharification conditions [8 % (w/v) substrate load, 133 U/g substrate load, 55.5 h incubation time]. The highest yield of reducing sugars was obtained in saccharifications combining A. oryzae crude extract with the commercial enzymatic cocktail. Monosaccharide analysis revealed glucose (157.08 mg/gsubstrate) and galacturonic acid (153.83 mg/gsubstrate) as the most abundant sugars released in the saccharified seaweed medium. Saccharified Ulva sp. was subsequently fermented by Lactiplantibacilus plantarum and Cyberlindnera jadinii (GRAS microorganisms). Saccharification led to a two-log growth increase for both yeast and LAB cultures, as well as increased acidification and FAN release by L. plantarum, compared to non-saccharified cultures. Enzymatic saccharification unlocks the full potential of seaweeds as fermentation substrates, transforming a challenging biomass into a rich foundation for microbial growth and functional food innovation.