Leading bacteria astray

François Barja‘s laboratory, at the Department of Botany and Plant Biology, is engaged in various pioneering projects in microbiology with major potential applications.

Production of cellulose fibers

“We have isolated an acetic bacterium, Komagataeibacter europaeus, which is able to produce cellulose in high amounts from wine, synthetic media or fruit juices”, says Dr. Barja. In natural conditions, this bacterium, strictly aerobic, produces cellulose fibers to protect itself from its environment and to be able to breathe.

Production of cellulose by K. europaeus bacteria – scanning electron microscopy (SEM)

 

The researchers use this micro-organism, rather than the standard bacterium Komagataeibacter xilinum, to produce cellulose because it is more efficient and more resistant to acetic acid. The cellulose is currently produced in a home-made device that allows pure fibers to be harvested in a semi-continuous way, without removing the bacteria K. europaeus.

“This cellulose is biocompatible and free from contaminants. It therefore does not require additional purification after the elimination of the bacteria”, explains the biologist. On a larger scale, this would translate into a low-cost and sustainable production. An ecological alternative that does not require the felling of trees for their wood, of which cellulose is the main constituent.

Cellulose fibers after the harvest

 

 

 

 

 

 

Countless potential applications

In the biomedical field, this type of cellulose can be used for 3D medical implants, artificial skin or blood vessels, as well as matrices allowing the three-dimensional growth of cells. At the technological level, this compound could be used to make loudspeaker membranes and flexible screens, among others.

“The addition of nanoparticles or other high value-added compounds modifies the physico-chemical properties of cellulose”, notes François Barja. For example, a biocompatible artificial skin used for the treatment of serious burn victims could be obtained by adding nanoparticles with antimicrobial properties.

In the presence of graphene, which consists of a monolayer of carbon atoms, the cellulose also becomes conductive, which opens the way to other applications such as optical or electronic composites.

Cellulose fibers and monolayers of graphene – SEM

 

 

 

 

Natural antiseptic solutions

The laboratory also develops solutions based on vinegar and plant extracts. “The components of vinegar, and especially acetic acid, are known for their bacteriostatic and bactericidal properties. The plant extracts we use can potentiate these effects”, says the biologist. This type of preparation is particularly effective for the disinfection of commercial, hospital or food surfaces, as well as for hand hygiene.

Production of vinegar

François Barja’s team is leading a pilot project to produce various aromas of vinegar and to isolate bacterial strains that are highly resistant to acetic acid and ethanol. The same strain of Komagataeibacter europaeus has won the prize of resistance because it is able to produce vinegar with a degree of acetic acid between 15 and 20, as compared to other acetic bacteria, which do not tolerate more than 10% acetic acid.

The researcher adds: “The K. europaeus strain is also capable of producing highly concentrated vinegar, with a reduced production time, which is an advantage in terms of transport and costs”.

More than 700 kg of fruits were peeled to obtain the mango vinegar…

 

 

 

 

 

The team of François Barja

 

 

 

 

 

Photographies : © François Barja, UNIGE