Using motile bacteria to generate a new bioplastic film with improved barrier properties over conventional plastic films

A paper published in the International Journal of Biological Macromolecules by the group led by Prof. Auxiliadora Prieto at the Centro de Investigaciones Biológicas Margarita Salas (CSIC), and first-authored by postdoctoral fellow Cristina Campano, describes a new biodegradable material, alternative to plastic films, which presents excellent barrier properties, high strength, and transparency. The design and development of this material are based on an innovative strategy that synergistically combines knowledge and techniques from the fields of microbial biotechnology and materials science.

The excellent barrier and mechanical properties of petrochemical plastics, their high durability, and their low cost make them indispensable materials in our lives today. However, the mismanagement of their waste and their massive use is causing major environmental problems with a direct effect on climate change and the destruction of terrestrial and marine ecosystems. This has been one of the driving forces behind the establishment of the European Green Deal strategy, which aims to curb climate change and environmental degradation in Europe.

Among the sectors in which plastics are used on a massive scale, the packaging sector stands out, in particular the manufacture of packaging, with a contribution of 40.5% of total applications. The generation of advanced biodegradable materials, generated from renewable sources that can be presented as potential substitutes for these plastic materials and thus reduce their impact on nature, is one of the most innovative alternatives to the petrochemical industry.

Campano et al. have used two bacterial biopolymers of broad biotechnological interest as a starting point. On the one hand, polyhydroxyalkanoates (PHAs), hydrophobic biopolyesters produced intracellularly by many bacterial genera stand out for the possibility of diversifying their properties by means of synthetic biology tools. On the other hand, bacterial cellulose (BC) is produced by the bacterium Komagataeibacter medellinensis, a hydrogel with a unique microporous cross-linked structure, as it presents homogeneous tunnels and layers with different fiber densities. The now-published study shows how PHA particles naturally produced by the bacterium Pseudomonas putida can be incorporated into the BC matrix, driven and directed by the same PHA-producing bacteria acting as process controllers.

As a result, biodegradable "bioplasticized" films with 4 times higher Young's modulus and 3 times lower oxygen permeability than the commercial polyethylene terephthalate (PET) films, widely used in the packaging field, have been generated.

Thanks to the versatility of the method devised in this study and the possibility of diversifying the chemical structure of PHA, it is possible to develop a wide variety of materials with properties on demand for very diverse fields of application, which exponentially expands their future prospects as potential substitutes for plastics of petrochemical origin.

The work is the result of a collaboration between researchers from CIB Margarita Salas and the Institute of Agrochemistry and Food Technology, both belonging to CSIC.

Reference: Gaining control of bacterial cellulose colonization by polyhydroxyalkanoate-producing microorganisms to develop bioplasticized ultrathin films. Cristina Campano, Virginia Rivero-Buceta, María José Fabra and M. Auxiliadora Prieto (2022) International Journal of Biological Macromolecules, 223 (A), 1495-1505. https://doi.org/10.1016/j.ijbiomac.2022.11.120