The food industry is increasingly demanding advanced and eco-friendly sustainable packaging materials with improved physical, mechanical and barrier properties. The currently used materials are synthetic and non-degradable, therefore raising environmental concerns. Consequently, research efforts have been made in recent years towards the development of bio-based sustainable packaging materials. In this review, the potential of nanocelluloses as nanofillers or as coatings for the development of bio-based nanocomposites is discussed, namely: (i) the physico-chemical interaction of nanocellulose with the adjacent polymeric phase, (ii) the effect of nanocellulose modification/functionalization on the final properties of the composites, (iii) the production methods for such composites, and (iv) the effect of nanocellulose on the overall migration, toxicity, and the potential risk to human health. Lastly, the technology readiness level of nanocellulose and nanocellulose based composites for the market of food packaging is discussed.

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A B S T R A C TThis work aimed at the optimization of bacterial nanocellulose (BNC) production by static culture, using Komagataeibacter xylinus BPR 2001 (K. xylinus). Response surface methodology -central composite design was used to evaluate the effect of inexpensive and widely available nutrient sources, namely molasses, ethanol, corn steep liquor (CSL) and ammonium sulphate, on BNC production yield. The optimized parameters for maximum BNC production were % (m/v): molasses 5.38, CSL 1.91, ammonium sulphate 0.63, disodium phosphate 0.270, citric acid 0.115 and ethanol 1.38% (v/v). The experimental and predicted maximum BNC production yields were 7.5 ± 0.54 g/L and 6.64 ± 0.079 g/L, respectively and the experimental and predicted maximum BNC productivity were 0.829 ± 0.046 g/L/day and 0.734 ± 0.079 g/L/day, after 9 days of static culture fermentation, at 30°C. The effect of surface area and culture medium depth on production yield and productivity were also studied. BNC dry mass production increased linearly with surface area, medium depth and fermentation time. So long as nutrients were still available in the culture media, BNC mass productivity was constant. The results show that a high BNC production yield can be obtained by static culture of K. xylinus BPR 2001 using a low-cost medium. These are promising conditions for the static industrial scale BNC production, since as compared to agitated bioreactors, higher productivities may be reached, while avoiding high capital and operating costs.

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BACKGROUND Most of the current materials used in food packaging are synthetic and non‐degradable, raising environmental issues derived from the accumulation of plastics in landfills/waterways. The food industry increasingly needs eco‐friendly sustainable materials that meet food‐packaging requirements. Bacterial nanocellulose (BNC), a biopolymer obtained by fermentation, offers very good mechanical properties and the ability to carry and deliver active substances. However, its water‐vapor permeability is too high for food‐packaging applications. In this work, a layered biodegradable composite based on BNC and polyhydroxyalkanoate (PHBV) was produced, attempting to improve its overall barrier properties. Polyhydroxyalkanoate is a biopolymer with high degree of hydrophobicity and biodegradability, and is also obtained by fermentation. Wet BNC membranes produced by static culture were plasticized by impregnation of solutions of either glycerol (BNCgly) or polyethylene glycol (MW600) (BNCPEG). The plasticized BNC was then coated with PHBV solution dissolved in formic acid, and oven dried at 148 °C. RESULTS Overall, PHBV coating on plasticized BNC reduced water vapor permeability significantly (from 0.990 to 0.032 g.μm.m−2.day−1.Pa−1) under 50% relative humidity. It increased the hydrophobicity (contact angle from 10–40° to 80–90°) but decreased the stiffness (from 3.1 GPa to 1.3 Gpa) of the composite. CONCLUSIONS Overall, the mechanical and barrier properties of the layered composite obtained were considered suitable for food‐packaging applications. The plasticizing (with glycerol or polyethylene glycol) of BNC significantly improved the mechanical performance and the PHBV coating reduced the water affinity (vapor and liquid state) on BNC. © 2022 Society of Chemical Industry.

In this work, recycled paper sludge (RPS), composed of non-recyclable fibres, was used as a carbon source for bacterial nanocellulose (BNC) production. The biomass was enzymatically hydrolysed with Cellic CTec 2 to produce a sugar syrup with 45.40 g/L glucose, 1.69 g/L cellobiose and 2.89 g/L xylose. This hydrolysate was used for the optimization of BNC fermentation by static culture, using Komagataeibacter xylinus ATCC 700178, through response surface methodology (RSM). After analysis and validation of the model, a maximum BNC yield (5.69 g/L, dry basis) was obtained using 1.50% m/v RPS hydrolysate, 1.0% v/v ethanol and 1.45% m/v yeast extract/peptone (YE/P). Further, the BNC obtained was used to produce composites. A mixture of an amino-PolyDiMethylSiloxane-based softener, polyethyleneglycol (PEG) 400 and acrylated epoxidized soybean oil (AESO), was incorporated into the BNC membranes through an exhaustion process. The results show that BNC composites with distinct performances can be easily designed by simply varying the polymers percentage contents. This strategy represents a simple approach towards the production of BNC and BNC-based composites.

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