One-step formation of three-dimensional macroporous bacterial sponges as a novel approach for the preparation of bioreactors for bioremediation and green treatment of water

Immobilisation of bacteria on or into a polymer support is a common method for the utilisation of bacteria
as biocatalysts for many biotechnological, medical and environmental applications. The main challenge in
this approach is the time taken for the formation of stable biofilms, and the typically low percentage of
bacterial cells present on or in the polymer matrix. In this work we propose a novel method for
producing a porous bacteria based structure with the properties of a sponge (bacterial sponge) that we
then use as a bioreactor for water treatment. Cryogelation has been used as a tool to create
macroporous (i.e. with pores in the range 10–100 mm), highly permeable systems with low diffusion
constraints and high bacterial content (more than 98% to total material content). A novel crosslinking
system was used to form stable bacterial sponges with a high percentage of live bacteria organized in
a 3D porous structure. The bacterial sponge was produced in a one step process and can be made from
one or several bacterial strains (in this case, two bacterial strains Pseudomonas mendocina and
Rhodoccocus koreensis (and a mixture of both) were used). Reduction of the total polymer content to
2% makes the system more sustainable and environmentally friendly under disposal as it can be simply composted. The bacterial sponges have good mechanical stability and cell viability, which enables repeated use of the materials for phenol degradation for up to five weeks. The material can be stored and transported in cryogenic conditions (80 C) for prolonged periods of time, retaining its bioremediation activity following 4–6 weeks of frozen storage. The proposed method of producing bioreactors with a high number of live immobilised bacteria, low polymer content and controlled 3D structure is a promising tool for developing novel materials based on active bacterial cells for various environmental, biotechnological, biological and medical applications.