Producing mixed linked xylooligosaccharides from red algae biomass through single-step enzymatic hydrolysis.

Background: The red alga Palmaria palmata is a rich source of sugar compounds, particularly mixed-linkage xylans present in the cell walls of the algae. In contrast to their terrestrial lignocellulosic counterparts, these xylans are more easily accessible. They can be hydrolyzed enzymatically into valuable xylooligosaccharides (XOS), known for their prebiotic, antioxidant, and immunomodulatory properties.

Results: This study introduces a simplified, one-step enzymatic process utilizing the endo-1,4-β-xylanase FO15_GH10 that directly hydrolyzes P. palmata biomass to produce XOS, eliminating the need for prior xylan extraction and improving efficiency. The exact structure of the resulting XOS was determined using NMR and MS/MS techniques. In addition, the xylosidase FO17_GH43 can be added to break down all residual 1,4-linked XOS. As a result, only 1,3- and mixed-linkage XOS (degree of polymerization (DP) 2-4) remains under simultaneous increase of the xylose obtained. Using FO15_GH10 alone, it was possible to produce approximately 17.6 (± 0.16) % (176 mg) XOS from 1 g of powdered biomass while combining both enzymes resulted in 22.6 (± 0.51) % (226 mg) XOS. Further optimization upon upscaling offers the possibility of achieving even greater improvements.

Conclusion: In summary, our one-step enzymatic approach offers an efficient and sustainable method for producing XOS directly from P. palmata biomass. This streamlined process overcomes the need for resource-consuming extraction processes. The further characterization of the obtained XOS and the potential to gain solely 1,3- and mixed-linkage XOS is paving the way for future studies on their functional properties.