Investigating the physical and mechanical properties of polylactic acid-nanocellulose nanocomposite film containing Lactobacillus casei probiotic bacteria

In this study, the survival of Lactobacillus casei probiotic bacteria added to polylactic acid-nanocellulose nanocomposite film during 16 days of storage in the refrigerator was investigated. For this purpose, three edible films including polylactic acid, polylactic acid + nano cellulose, polylactic acid + nano cellulose+ Lactobacillus casei (9 log CFU/g) were prepared and the physical and mechanical characteristics of the films as well as the survival of Lactobacillus casei bacteria were investigated. The results of the mechanical test showed that the use of probiotic bacteria decreased the tensile strength and elongation at break of the polylactic acid-nanocellulose film (P < 0.05), but the addition of nanocellulose improved the mechanical properties of the polylactic acid film. The results of physical tests including humidity, solubility, water vapor permeability showed that the addition of probiotic bacteria and nanocellulose improved the physical properties of the film, but the opacity of the films increased (P<0.05). According to the results of the present study, with the increase in storage time, the survival of probiotic bacteria in the nanofilm decreased, and at the end of the storage period, its values were equal to 6.12 log CFU/g, but it was within the permissible range (6 log CFU/g).Therefore, the composition of Lactobacillus casei probiotic strain in the edible film can be its suitable carrier at refrigerator temperature