Citric acid crosslinked ternary blended (polyvinyl alcohol, lignin, lemongrass essential oil/nanoemulsions) biopolymeric hydrogel films: structural, functional, antioxidant, antifungal and biodegradable properties

Rice straw is chemically constituted of three major biopolymers i.e. cellulose, hemicellulose and lignin which hold immense potential for conversion into various high-value materials. In the present study, attempts were made to valorize lignin, an aromatic phenolic polymer, via fabricaton of biopolymeric films. For this, alkali lignin was extracted from rice straw and lemongrass essential oil nanoemulsions were prepared with mean droplet diameter (spherical shape as revealed by transmission electron micrograph) and polydispersity index, 123.4?nm and 0.125, respectively. Citric acid crosslinked ternary blended i.e. polyvinyl alcohol, lignin, lemongrass essential oil/nanoemulsions biopolymeric hydrogel films were fabricated and their physical, structural and functional properties were assessed. The highest tensile strength and elongation at break were 24.31?MPa and 33.08% for OL₃ (oil with 3000?ppm lignin) and NL₂ (nanoemulsion with 2000?ppm lignin), respectively. NL₂ films exhibited highest %DPPH radical scavenging activity (78.05%), highest % inhibition in size (74%) and number (95.94%) of colony forming units of Aspergillus niger. All the synthesized films showed appreciable biodegradability in soil with maximum % weight loss experienced in NL₂ films (91.11%). These biopolymeric hydrogel films can be explored for use as sustainable alternatives to synthetic plastic wraps used extensively in food packaging industries to minimize plastic consumption.

Graphical abstract