Eco-friendly process for the isolation of biopolymers from agricultural residues

A process for the isolation of biopolymers from agricultural residues, wherein the process comprises the steps:

• a) obtaining and pulverizing dried biomass to size in the range of 0.1 to 0.15 mm and extracting using petroleum ether (60-80 degree C.) or hexane in a first phase and one or more alcohol in a second phase to obtain a de-waxed biomass extract;
• b) partitioning the de-waxed biomass extract with water to obtain a nonpolar soluble portion and a raffinate portion;
• c) treating the nonpolar soluble portion with fuller's earth followed by filtration and concentration of filtrate to obtain neutral lipids;
• d) the raffinate portion is subsequently concentrated and solubilized with aqueous alcohol followed by partition with one or more organic solvent to obtain an organic solvent soluble portion, and an aqueous portion;
• e) treating the organic solvent soluble portion with fuller's earth followed by filtration and concentration of filtrate to obtain polar lipids;
• f) mixing imidazole with one or more organic acid in equimolar ratio in alcohol followed by refluxing or stirring at a temperature in the range of 65 to 90 degree C. for a period of 30 minutes to 1 hour to obtain an organic acidified imidazole:water (2:1 to 1:1) solvent system after removing the alcohol and adding water content;
• g) treating the aqueous portion as obtained in step [d] with the organic acidified imidazole:water (2:1 to 1:1) solvent system as obtained in step [f] at a temperature in the range of 90 to 120 degree C. for a period of 30 minutes to 2 hours without stirring to obtain a de-lignified biomass and a solution containing lignin;
• h) precipitating lignin from the solution as obtained in step [g] by dilution with water and filtering or centrifuging and washing the precipitate to isolate pure lignin;
• i) mixing 0.1 M of imidazole solution with 0.1 M of one or more alkali in water followed by refluxing or stirring at a temperature in the range of 90 to 110 degree C. for a period of 30 minutes to 1 hour to obtain a solvent system of 0.1M to 0.2M imidazole-alkali in water;
• j) treating the de-lignified biomass as obtained in step [g] with the solvent system as obtained in step [i] at a temperature in the range of 60 to 90 degree C. for a period of 30 minutes to 2 hours without stirring followed by filtering to obtain a filtrate containing hemicellulose and a residue containing cellulose;
• k) neutralizing the filtrate as obtained in step [j] with one or more organic acid followed by addition of one or more alcohols to precipitate the hemicellulose followed by filtration or centrifugation and washing the precipitate with alcohol to obtain pure hemicellulose;
• l) washing the residue as obtained in step [j] with water to obtain the pure cellulose.