4-01: Concomitant production of value-added polysaccharides and bio-oil from algal feedstock

To make algal bio-fuel economically viable extraction of value added co-products along with oil is absolute necessity. Algal polysaccharides present a wide array of potential applications as emulsifiers, stabilizers or thickening and nutraceutical agents. Therefore, polysaccharides can be considered as potent candidate for value added co-product. The major bottle neck in algal co-product development is the lack of efficient separation technology. To address this issue a unique two-step sequential hydrothermal extraction technology (SSHTE) for simultaneous production of value-added polysaccharides and bio-oil from algal-biomass is developed. First step involves the subcritical water extraction of valuable algal (Chlorella sorokiniana) polysaccharides at 160^°C temperature. Polysaccharide rich water extract is removed and precipitated with ethanol.  In next step extracted biomass is liquefied to bio-oil at 300 ^°C. Yield of bio-oil by SSHTE and direct hydrothermal liquefaction (DHTL) is 23.60 % and 27.80 % of dry weight respectively. In SSHTE method bio char production is remarkably low. Bio-char produced by SSHTE method is 63% less than DHTL method. Comparative GC-MS, GLC, NMR and FT-IR analysis of the bio-oil extracted by SSHTE with DHTL showed no significant changes. Elemental analysis of the SSHTE bio-oil revealed the presence of 70% carbon very low nitrogen (0.78%) and 11 % oxygen. Polysaccharide (26% dw) isolated by the current experiments exhibits emulsifying and anti-inflammatory properties therefore, lending future scope to develop them as emulsifier or bioactive agent. This method nonetheless, can be described as the first step towards concomitant production of non-lipid value added co-products and bio-oil from algal biomass.