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Abstract:
Marine seaweeds increasingly grow into extensive algal blooms, which are
detrimental to coastal ecosystems, tourism and aquaculture. However,
algal biomass is also emerging as a sustainable raw material for the
bioeconomy. The potential exploitation of algae is hindered by our
limited knowledge of the microbial pathways-and hence the distinct
biochemical functions of the enzymes involved-that convert algal
polysaccharides into oligo- and monosaccharides. Understanding these
processes would be essential, however, for applications such as the
fermentation of algal biomass into bioethanol or other value-added
compounds. Here, we describe the metabolic pathway that enables the
marine flavobacterium Formosa agariphila to degrade ulvan, the main cell
wall polysaccharide of bloom-forming Ulva species. The pathway involves
12 biochemically characterized carbohydrate-active enzymes, including
two polysaccharide lyases, three sulfatases and seven glycoside
hydrolases that sequentially break down ulvan into fermentable
monosaccharides. This way, the enzymes turn a previously unexploited
renewable into a valuable and ecologically sustainable bioresource.
