Abstract
In the present study, 199 pre-selected Carbohydrate-Active enZymes (CAZymes) and sulfatases were assessed, either alone or in combination, to evaluate their capacity to disrupt Laminaria digitata cell wall, with the consequent release of interesting nutritional compounds. A previously characterized individual alginate lyase, belonging to the family 7 of polysaccharide lyases (PL7) and produced by Saccharophagus degradans, was shown to be the most efficient in the in vitro degradation of L. digitata cell wall. The alginate lyase treatment, compared to the control, released up to 7.11 g/L of reducing sugars (p < 0.001) and 8.59 mmol/100 g dried alga of monosaccharides (p < 0.001), and reduced cell wall fluorescence intensity by 39.1% after staining with Calcofluor White (p = 0.001). The hydrolysis of gel-forming polymer alginate by the alginate lyase treatment could prevent the trapping of fatty acids and release beneficial monounsaturated fatty acids, particularly 18:1c9 (p < 0.001), to the extracellular medium. However, no liberation of proteins (p > 0.170) or pigments (p > 0.070) was observed. Overall, these results show the ability of an individual alginate lyase, from PL7 family, to partially degrade L. digitata cell wall under physiological conditions. Therefore, this CAZyme can potentially improve the bioavailability of L. digitata bioactive compounds for monogastric diets, with further application in feed industry.
Highlights
In the present study, 199 pre-selected Carbohydrate-Active enZymes (CAZymes) and sulfatases were assessed, either alone or in combination, to evaluate their capacity to disrupt Laminaria digitata cell wall, with the consequent release of interesting nutritional compounds
The catalytic activity and the biochemical properties of the majority of the candidates were previously described in the literature and their amino acid sequences can be accessed in Genbank
All soluble protein fractions were enriched by a high throughput Immobilised Metal Affinity Chromatography (IMAC) protocol before the activity screens
Summary
199 pre-selected Carbohydrate-Active enZymes (CAZymes) and sulfatases were assessed, either alone or in combination, to evaluate their capacity to disrupt Laminaria digitata cell wall, with the consequent release of interesting nutritional compounds. No liberation of proteins (p > 0.170) or pigments (p > 0.070) was observed Overall, these results show the ability of an individual alginate lyase, from PL7 family, to partially degrade L. digitata cell wall under physiological conditions. Brown macroalgae have a distinct carbohydrate-rich cell-wall[9,10], which comprises up to 45% DM of alginate and fucose-containing sulphated polysaccharides (FCSPs) (fucans or homofucans and fucoidans or heterofucans), as well as small amounts of cellulose (1 to 8% DM)[11], β-1,3 glucans, unbranched mixed-linkage β-D-glucans (1,3-and-1,4-β-Dglucose residues) masked by alginate[12] and arabinogalactans linked to proteins[13]. Alginate cross-links with phenolic compounds and constitutes gel-forming and hydroscopic polymers that control cell wall rigidity[11] These polymers form a network that embed fucose-containing sulphated polysaccharides. The presence of complex polysaccharides in seaweed cell walls can decrease the rate of algae biomass hydrolysis during the production of renewable energies, reducing bioethanol and biogas y ields[17]
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