Development and Characterization of Yeast-Incorporated Antimicrobial Cellulose Biofilms for Edible Food Packaging Application

Abstract

The unique properties and advantages of edible films over conventional food packaging have led the way to their extensive exploration in recent years. Moreover, the incorporation of bioactive components during their production has further enhanced the intrinsic features of packaging materials. This study was aimed to develop edible and bioactive food packaging films comprising yeast incorporated into bacterial cellulose (BC) in conjunction with carboxymethyl cellulose (CMC) and glycerol (Gly) to extend the shelf life of packaged food materials. First, yeast biomass and BC hydrogels were produced by Meyerozyma guilliermondii (MT502203.1) and Gluconacetobacter xylinus (ATCC53582), respectively, and then the films were developed ex situ by mixing 30 wt.% CMC, 30 wt.% Gly, 2 wt.% yeast dry biomass, and 2 wt.% BC slurry. FE-SEM observation showed the successful incorporation of Gly and yeast into the fibrous cellulose matrix. FTIR spectroscopy confirmed the development of composite films through chemical interaction between BC, CMC, Gly, and yeast. The developed BC/CMC/Gly/yeast composite films showed high water solubility (42.86%). The yeast-incorporated films showed antimicrobial activities against three microbial strains, including Escherichia coli, Pseudomonas aeruginosa, and Saccharomyces aureus, by producing clear inhibition zones of 16 mm, 10 mm, and 15 mm, respectively, after 24 h. Moreover, the films were non-toxic against NIH-3T3 fibroblast cells. Finally, the coating of oranges and tomatoes with BC/CMC/Gly/yeast composites enhanced the shelf life at different storage temperatures. The BC/CMC/Gly/yeast composite film-coated oranges and tomatoes demonstrated acceptable sensory features such as odor and color, not only at 6 °C but also at room temperature and further elevated temperatures at 30 °C and 40 °C for up to two weeks. The findings of this study indicate that the developed BC/CMC/Gly/yeast composite films could be used as edible packaging material with high nutritional value and distinctive properties related to the film component, which would provide protection to foods and extend their shelf life, and thus could find applications in the food industry.

Keywords: antimicrobial activity; bacterial cellulose; biocompatibility; carboxymethyl cellulose; edible film; food packaging; glycerol; yeasts.

Figure 1

Stress–strain curves of (A) pristine BC and BC/CMC composite film and (B) BC/CMC/Gly and BC/CMC/Gly/yeast composite films.

Figure 2

FE-SEM micrographs of surfaces of (A) pristine BC, (B) BC/CMC, (C) BC/CMC/Gly, and (D) BC/CMC/Gly/yeast films. The inset images show the respective freeze-dried samples.

Figure 3

FT-IR spectra of pristine BC, CMC, BC/CMC, glycerol, BC/CMC/Gly, yeast, and BC/CMC/Gly/yeast.

Figure 4

TGA curves of BC, BC/CMC/Gly, and BC/CMC/Gly/yeast films.

Figure 5

(A–C) Antimicrobial activity of BC/CMC/Gly/yeast composite films against Gram-positive (S. aureus) and Gram-negative bacteria (P. aeruginosa and E. coli) determined via disc diffusion method. A pure yeast extract and BC/CMC/Gly film were used as the positive control and negative control, respectively. (D) A quantitative presentation of inhibition zones produced by the sample and control against the tested microorganisms, * p < 0.05 and at ** p < 0.01.

Figure 6

Viability of NIH-3T3 fibroblasts on pristine BC, BC/CMC, BC/CMC/Gly, and BC/CMC/Gly/yeast films after incubation for 1, 3, and 5 days, * p < 0.05. The absorption was recorded at 570 nm for all samples.

Figure 7

The results of preliminary analysis of (A) fruit coating and (B) evaluation of acceptance for the control (uncoated tomatoes) and pristine BC, BC/CMC, and BC/CMC/Gly films evaluated at 30 °C for two weeks.

Figure 8

The photographs of uncoated oranges (control), BC-coated oranges (Film-0), and BC/CMC/Gly/yeast-coated oranges (Film-1) stored at (A) 30 °C, (B) 40 °C, (C) 6 °C, and (D) room temperature (20 to 25 °C) for different time intervals.

Figure 9

Evaluation of acceptance of uncoated oranges (control), BC-coated oranges (Film-0), and BC/CMC/Gly/yeast-coated oranges (Film-1) stored at (A) 30 °C, (B) 40 °C, (C) 6 °C, and (D) room temperature (20 to 25 °C for different time intervals.

Figure 10

The photographs of uncoated tomatoes (control), BC-coated tomatoes (Film-0), and BC/CMC/Gly/yeast-coated tomatoes (Film-1) stored at (A) 6 °C, (B) 40 °C, (C) 30 °C, and (D) room temperature (20 to 25 °C) for different time intervals.

Figure 11

Evaluation of overall acceptability of uncoated tomatoes (control), BC-coated tomatoes (Film-0), and BC/CMC/Gly/yeast-coated tomatoes (Film-1) stored at (A) 6 °C, (B) 40 °C, (C) 30 °C, and (D) room temperature (20 to 25 °C) for different time intervals.