Bioconversion of the invasive seaweed Rugulopteryx okamurae into enzymes and polyhydroxyalkanoates

The invasive macroalgae Rugulopteryx okamurae has been used as raw material for the production of hydrolytic enzymes and polyhydroxyalkanoates (PHA), bioplastic precursors. The fungus Aspergillus oryzae, grown in solid state fermentation (SSF) on the macroalga biomass, produced several hydrolytic enzymes, mainly xylanase and alginate lyase. Also, SSF was used as biological pretreatment of the macroalga to enhance the release of fermentable sugars after enzyme hydrolysis for subsequent PHA production. To increase sugar concentration and reduce the total cost of the process, the enzyme hydrolysis was performed at a high solid load and stirring rate, reducing the enzyme cocktail dose used by 63.5 %. At these conditions, the hydrolysate contained 18.52 g/L of reducing sugars, which were fermented with Cupriavidus necator, reaching a maximum of 288.0 mg PHA/L at 24 h.