Development of Antimicrobial Blends of Bacteria Nanocellulose Derived from Plastic Waste and Polyhydroxybutyrate Enhanced with Essential Oils

Abstract

The escalating global concern regarding plastic waste accumulation and its detrimental environmental impact has driven the exploration of sustainable alternatives to conventional petroleum-based plastics. This study investigates the development of antimicrobial blends of bacterial nanocellulose (BNC) derived from plastic waste and polyhydroxyalkanoates (PHB), further enhanced with essential oils. The antimicrobial activity of the resulting BNC/PHB blends was tested in vitro against Escherichia coli, Staphylococcus aureus, and Candida albicans. The incorporation of essential oils, particularly cinnamon oil, significantly enhanced the antimicrobial properties of the BNC/PHB blends. The BNC with 5% PHB blend exhibited the highest antifungal inhibition against C. albicans at 90.25%. Additionally, blends with 2% and 10% PHB also showed antifungal activity, inhibiting 68% of C. albicans growth. These findings highlight the potential of incorporating essential oils into BNC/PHB blends to create effective antimicrobial materials. The study concludes that enhancing the antimicrobial properties of BNC/PHB significantly broadens its potential applications across various sectors, including wound dressings, nanofiltration masks, controlled-release fertilizers, and active packaging.

Keywords: antimicrobial blends; bacterial nanocellulose; biopolymers; polyhydroxyalkanoates.

Figure 1

Antimicrobial activity of essential oils against (A) E. coli, (B) S. aureus, and (C) C. albicans in liquid culture. The absorbance values were measured at 530 nm for S. aureus and 630 nm for E. coli and P. aeruginosa after 24 h of incubation. The dashed lines represent the positive (red) and negative (green) controls, while the dotted line represents the MIC threshold, and triangles indicate the minimum inhibitory concentration (MIC) for each essential oil.

Figure 2

Zones of inhibition of examined essential oils against E. coli and S. aureus in a Ø 89.42 mm standard petri dish. Arrows represent the halo’s radius.

Figure 3

Antimicrobial activity of essential oils against E. coli and S. aureus. (A) Box plot of the antimicrobial activity of the essential oils (B) Heatmap of the antimicrobial activity of the essential oils against E. coli and S. aureus.

Figure 4

Visual and Physical Characteristics of BNC Blends with PHB (top) and PHA-enriched biomass (bottom), in a Ø 89.42 mm standard petri dish.

Figure 5

Materials 2.5D topographic simulations at 15× magnification of BNC (A), BPHB2 (B), BPHB5 (C), and BPHB10 (D).

Figure 6

SEM images and pore size distribution analysis of BNC/PHB blends. (A) BNC, (B) BPHB2, (C) BPHB5, and (D) BPHB10. SNOW algorithm segmentation of (E) BNC, (F) BPHB2, (G) BPHB5, and (H) BPHB10 from same figure from (A–D), respectively, which the color gradient visualizes pore size variation within and between materials red (largest pores) to blue/purple (smallest); (I) Cumulative pore size distributions of BNC/PHB blends.

Figure 7

Examples of stress-strain tensile curves obtained, grouped by color and duplicates differentiated by dashed and dotted lines.

Figure 8

TGA curves of examined BNC blends: BNC/PHB blends.

Figure 9

FT-IR spectra of examined BNC blends.

Figure 10

Microbial growth graph depicting cultures of E. coli (A), S. aureus (B), and C. albicans (C) as positive controls, alongside cultures growing in the presence of BNC-based blends with and without the addition of Cinnamon oil. Growth percentages are calculated relative to the average growth of the positive controls, set at 100%.

Figure 11

Effects of Bacterial Nanocellulose and BNC-PHB Composites on Microbial Biofilms. The samples in red indicate the absence of anti-biofilm activity.

Figure 12

Survival analysis of C. elegans AU37 exposed to BNC/PHB materials. Kaplan–Meier survival curves for (A) all experimental groups and (B) groups with statistically significant differences.