Recovery and characterization of cellulose microfibers from fallen leaves and evaluation of their potential as reinforcement agents for production of new biodegradable packaging materials

In the present work, cellulose microfibers (CMFs) isolated from fallen autumn leaves of cherry plum (<i>Prunus cerasifera pissardii nigra</i>), white mulberry (<i>Morus alba)</i> and plane (<i>Platanus orientalis</i>) trees were characterized and used as reinforcement agents in sodium alginate-based biodegradable films. Fourier transform infrared spectroscopy (FT-IR) characterization showed that the CMFs were successfully isolated from the leaves with high purity. The extracted CMFs had a particle size ranging from 321.20 nm to 632.26 nm and negative zeta potential values (-27.33 to -21.40). The extraction yield of CMFs ranged from 19.53% to 26.00%. Incorporation of the leaf-derived CMFs into sodium alginate based films (1%, w:w) increased their tensile strength (from 153.73 to 187.78 MPa) and elongation at break values (from 105.97% to 89.90%) and significantly decreased oxygen (from 121.46 to 75.56 meq kg^-1) and water vapor permeabilities (from 2.36 to 1.60 g mm h^-1 m^-2 kPa^-1)(<i>p</i> < 0.05). Furthermore, the supplementation of CMFs into the biopolymer matrix had no significant effect on the color (<i>L*:</i> 85.35-85.67; <i>a*:</i> -0.75-0.71; <i>b*</i>: 4.23-4.94) and moisture content (44.64-48.42%) of the film samples, although the thickness increased (40.33-94.66 μm). Scanning electron microscopy (SEM) images showed that CMFs were homogeneously dispersed in the film matrix. Overall, this study confirms that fallen cherry plum, white mulberry, and plane leaves are valuable sources of CMFs which could be used in the manufacturing of biodegradable nanocomposite films as reinforcement agents.