An α-glucan isolated as a co-product of biofuel by hydrothermal liquefaction of Chlorella sorokiniana biomass

Complete use of all major components of biomass is critical to make algal biofuel feasible. Therefore, a sequential hydrothermal liquefaction process was developed as an extraction technology to fractionate the polysaccharides and the lipids from algal cells. This technology was used to process Chlorella sorokiniana biomass by extracting polysaccharides from the biomass at lower temperature followed by liquefaction of the extracted residue to bio-oil at higher temperatures. The extracted polysaccharides were characterized to evaluate its potential industrial applications. Structural and chemical characteristics of crude polysaccharides were determined by different spectroscopic analysis. Monosaccharide composition and linkage analysis revealed that > 90% of the polysaccharide is composed of 1 → 4 linked glucan. As quantified based on molecular weight cut off of the dialysis bag, 68–70% of the ethanol insoluble polysaccharide showed to have a molecular weight > 10,000 g/mol. The polysaccharide exhibited pseudoplastic behavior at 0.05 g/ml which could be maintained over a NaCl concentration of 0.1 to 3 M. Thermogravimetric analysis (TGA) and differential scanning calorimetric analysis (DSC) were also conducted to evaluate the thermal property of the polysaccharide. Various industrial applications were suggested based on the measured characteristics of the polysaccharides.