Development of biocompatible and biodegradable films with high gas barrier properties are essential for its uses in stringent food packaging applications. generally, packaging is essential to protect food from the environmental damage. present invention discloses the synthesis of biodegradable, non-toxic polysaccharide based additive within 30 min by a simple, efficient, industrially viable and cost-effective technique, which is capable to improve gas permeability upto ~10 folds after dispersing of small wt% (upto ~5 wt%) in hydrophobic polymers using melt extrusion process. the gas permeability values of such an excellent biodegradable polymer films are comparable to that of commercial polyethylene terephthalate (pet) and other conventional polymers of its kind. the melt extrusion of biodegradable polymer films has been done at the same processing temperature as compare to that of hydrophobic polymers by using twin screw extruder with l/d ratio of 48 and throughput of ~10 kg polymer per hour. in a particular case, the synthesis of lactic acid oligomer-grafted-chitosan (olla-g-ch), a nanoamphiphilic molecule has been done by in situ condensation polymerization, which is further used as a nano-filler in poly (lactic acid) (pla) films to improve the multiple properties. the uniform dispersion of nanoamphiphilic olla-g-ch molecules has been detected with self-assembled micelles having size as low as ∼20 nm and as high as ∼150 nm with core-shell morphology in pla matrix. the gas permeability results also support the surface morphology and the % reduction in oxygen permeability is calculated up to ∼82% at 25°c and 0% rh. however, the % reduction value in oxygen permeability increases up to ∼99% at 15°c and 0% rh due to the reduction in solubility of oxygen molecules and improvement in crystal nucleation density due to availability of nano-nucleating sites. ultimate tensile strength (uts) of poly (lactic acid)/lactic acid oligomer-grafted-chitosan (pla/olla-g-ch) bionanocomposite films are relatively comparable to that of pla, however, elongation at break is improved significantly. the glass transition temperature (tg) of bionanocomposites is decreased by more than 18°c with an increase in olla-g-ch loading, which indicates the improved plasticization characteristics of pla matrix. the onset of thermal degradation of pla/olla-g-ch bionanocomposite films is also found comparable to that of pla film. in this way, pla/olla-g-ch bionanocomposite films can be one of the best substitutes to increase food shelf life in stringent food packaging applications.