Self-Grown Bacterial Cellulose Capsules Made through Emulsion Templating

Abstract

Microcapsules made of synthetic polymers are used for the release of cargo in agriculture, food, and cosmetics but are often difficult to be degraded in the environment. To diminish the environmental impact of microcapsules, we use the biofilm-forming ability of bacteria to grow cellulose-based biodegradable microcapsules. The present work focuses on the design and optimization of self-grown bacterial cellulose capsules. In contrast to their conventionally attributed pathogenic role, bacteria and their self-secreted biofilms represent a multifunctional class of biomaterials. The bacterial strain used in this work, Gluconacetobacter xylinus, is able to survive and proliferate in various environmental conditions by forming biofilms as part of its lifecycle. Cellulose is one of the main components present in these self-secreted protective layers and is known for its outstanding mechanical properties. Provided enough nutrients and oxygen, these bacteria and the produced cellulose are able to self-assemble at the interface of any given three-dimensional template and could be used as a novel stabilization concept for water-in-oil emulsions. Using a microfluidic setup for controlled emulsification, we demonstrate that bacterial cellulose capsules can be produced with tunable size and monodispersity. Furthermore, we show that successful droplet stabilization and bacterial cellulose formation are functions of the bacteria concentration, droplet size, and surfactant type. The obtained results represent the first milestone in the production of self-assembled biodegradable cellulose capsules to be used in a vast range of applications such as flavor, fragrance, agrochemicals, nutrients, and drug encapsulation.