Important Chemical Products from Macroalgae (Ascophyllum nodosum) Biorefinery by Assistance of Microwave Technology

The biorefinery is an important concept for the development of alternative routes to a range of interesting and important materials from renewable resources. It ensures that the resources are used fully and that all parts of them are valorized. The project will develop this concept, using macroalgae Ascophyllum nodosum as an example. The project focuses on valuable chemicals (e.g. fucoidan, alginate and sugars) and fuels (bioethanol and biochar) from macroalgae by assistance of microwave technology. Microwave assisted extraction of fucoidan proves that fucoidan could be extracted in 5-30 min by microwave heating from 90 oC to 150 oC, and the highest yield (16.08%) was obtained at 120 oC, 15 min. The compositional characterization of fucoidan was carried out, and antioxidant activity test shows that fucoidan could potentially be a resource for natural antioxidant. Microwave assisted extraction of alginate proves that alginate could be extracted successfully under low temperature (60-90 oC) - open vessel system and high temperature (100-140 oC) - closed vessel system, respectively. The results show that high temperature extraction had higher yield in less time compared with low temperature extraction, and Mw from both extraction were similar, 180 kDa – 220 KDa. Microwave assisted hydrolysis of Ascophyllum nodosum shows that the optimal condition for saccharification was 0.4 M H2SO4, 3.13% (w/v) of biomass loading, reaction temperature at 150 oC for 1 min holding time, resulting in 127 mg/g monosaccharides of seaweed being released. An ethanol concentration of 5.57 g/L and a conversion efficiency of 60.7% were achieved after fermentation. More than 50% energy yield of alga residue was recovered after hydrolysis, and the energy densification ranged from 1.4 to 1.7, with HHVs from about 19 - 24 MJ/kg. In addition, a step-by-step extraction and purification method was developed, in which fucoidan, alginate, sugar and biochar could be separated subsequently.