The enzymatic ulvan depolymerisation system from the alga-associated marine flavobacterium <i>Formosa agariphila</i>

Green macroalgae represent an attractive source of renewable carbon. Conversion of green algal biomass to useful products requires depolymerisation of the cell wall polysaccharide ulvan. The enzymatic depolymerisation of ulvan is not fully understood and only few enzymes involved in this process have been reported. In this study the first model for ulvan depolymerisation and utilization was built based on a polysaccharide utilization locus from the alga-associated flavobacterium Formosa agariphila. It was also shown that F. agariphila, is able to grow using biomass from the green macroalga Ulva lactuca as its sole carbon source, and enzymes with ulvanase activity are induced by the presence of algal biomass in the culture medium. Enzymes for ulvan depolymerisation from F. agariphila, including an ulvan lyase, an unsaturated glucuronyl hydrolase, a xylosidase and two rhamnosidases, were cloned using the PaperClip DNA assembly method and expressed in active form in Escherichia coli. These results represent a first step for the design of a microorganism capable of utilizing green macroalgal biomass for the production of biofuels and other valuable bio-products.