Bacterial cellulose from side-streams of Kombucha fermentation as sustainable bio-based reinforcement in thermoplastic-matrix composites
Topic(s) : Material science
Co-authors :
Edoardo EDOARDO ZONTA (ITALY), Andrea DORIGATO (ITALY), Giulia FREDI (ITALY)Abstract :
The extensive use of plastic materials, especially in the food packaging sector, causes environmental problems related both to the source of these materials and to their non-biodegradable nature. Cellulose, being the most abundant renewable biopolymer, is gaining interest food packaging field. Among the different types of cellulose, bacterial cellulose (BC) offers many advantages which allows the diverse applications of BC in sectors like biomedical, food industry, environmental, and several others. Its properties can be tuned according to the type of microbial strain, fermentation conditions, and post-synthesis processing, making this biopolymer a potential alternative to non-biodegradable synthetic materials [1]. Nevertheless, the development and use of BC films in the food packaging sector are limited due to the low elasticity of the material and the difficult scalability of the production process [2].
The focus of this work concerned the production of BC films for food packaging applications, employing an innovative and efficient technique that enables large-scale manufacturing of films with adjustable properties. Composite films of BC, polyvinyl alcohol (PVA), and chitosan were produced through a mechanical wet mixing technique, followed by a casting and drying process. This method involves advantages such as the simultaneous addition of fillers and other additives, decreased production time, and a higher range of additive concentrations, compared to other methods for the modification of BC. In the first set of samples, different amounts of PVA (20, 40, 60, 80 wt.%) were blended with BC, while in the second, 5 wt.% of chitosan was added maintaining the proportion between BC and PVA. The final samples were experimentally tested considering the chemical, thermal, morphological, mechanical, optical, antimicrobial, and biodegradability properties.
The microstructural analysis evidenced that BC morphology remains unaffected by the wet mixing process. The interaction between BC, PVA, and chitosan was demonstrated by chemical and thermal analysis. The increase in PVA content led to an increase in water solubility (WS), water absorption capacity (WAC), water vapor permeability (WVP), and contact angle (CA). In contrast, the addition of chitosan caused a decrease in all the water-related properties, as well as improved thermal stability. According to the tensile tests, the addition of PVA to BC reduced the stress and strain at break, as well as the stiffness, while the addition of chitosan increased the elastic modulus. Moreover, optical, antimicrobial, and biodegradability tests confirmed the possibility of changing film properties by varying its composition. This work showcases the potential of BC composite materials and demonstrates the flexibility of the wet mixing process in tailoring the characteristics of the prepared films, expanding its applications in the food packaging sector.
The focus of this work concerned the production of BC films for food packaging applications, employing an innovative and efficient technique that enables large-scale manufacturing of films with adjustable properties. Composite films of BC, polyvinyl alcohol (PVA), and chitosan were produced through a mechanical wet mixing technique, followed by a casting and drying process. This method involves advantages such as the simultaneous addition of fillers and other additives, decreased production time, and a higher range of additive concentrations, compared to other methods for the modification of BC. In the first set of samples, different amounts of PVA (20, 40, 60, 80 wt.%) were blended with BC, while in the second, 5 wt.% of chitosan was added maintaining the proportion between BC and PVA. The final samples were experimentally tested considering the chemical, thermal, morphological, mechanical, optical, antimicrobial, and biodegradability properties.
The microstructural analysis evidenced that BC morphology remains unaffected by the wet mixing process. The interaction between BC, PVA, and chitosan was demonstrated by chemical and thermal analysis. The increase in PVA content led to an increase in water solubility (WS), water absorption capacity (WAC), water vapor permeability (WVP), and contact angle (CA). In contrast, the addition of chitosan caused a decrease in all the water-related properties, as well as improved thermal stability. According to the tensile tests, the addition of PVA to BC reduced the stress and strain at break, as well as the stiffness, while the addition of chitosan increased the elastic modulus. Moreover, optical, antimicrobial, and biodegradability tests confirmed the possibility of changing film properties by varying its composition. This work showcases the potential of BC composite materials and demonstrates the flexibility of the wet mixing process in tailoring the characteristics of the prepared films, expanding its applications in the food packaging sector.