The word ‘cellulose’ generally brings to mind plant-derived fibres, but the biopolymer can be produced by bacteria too. Plant cellulose is ubiquitous, but it suffers from drawbacks such as contamination with lignin, wax and hemicellulose.
Bacterial cellulose (BC), on the other hand, is free from impurities such as lignin and wax, shows water retention capacity and other mechanical properties. BC, with its leather-like looks and properties, is gaining popularity the world over.
Although BC has been known for decades, research into it has perked up in the last 2-3 years because the world wants materials with better functionalities and looks, and made without harming animals. Scientists are trying to solve two issues — how to make BC cheaper; and how to make it more functional. Also, the search for more climate-friendly materials is leading scientists to BC. Leather making involves using a lot of water and chemicals; animals also let out huge amounts of methane.
BC can replace leather in the making of products such as bags. ‘Vegan leather’ is gaining ground in the West. German company ScobyTec and Brazilian firm Intervém Design manufacture fashion products such as bags and cachepots using BC.
BC polymers are finding use in other industries such as biomedicine, too. “BC, fabricated with gelling materials like sodium alginate, chitosan, polyethylene glycol and gelatin, can also be used as a carrier for bioactive compounds such as antibiotics,” says a scientific paper produced by Dr Ahmed Saleh et al of the National Research Centre, Egypt, and published in Nature. Wound dressing is emerging as a key application of BC.
“BC and BC-derived materials are essential in developing pure and environmentally safe functional materials,” says another paper on the subject, published by scientists of the Chennai-based Central Leather Research Institute, which comes under the Council for Scientific and Industrial Research (CSIR).
Dr Debasis Samanta, one of the authors of the CLRI paper, told Quantum that the institute’s efforts have been in the direction of combining other polymers with BC. Samanta and his team have succeeded in combining poly-triazole with BC using click chemistry techniques. He said polyurethane can be similarly “immobilised” into BC and such material would be cheaper.
“The high cost of BC production represents a challenge in its commercial adoption,” says Dr Saleh in his paper. One way of hammering down costs is to increase the yield, which means identifying strains of bacteria that can produce more.
The most used bacteria for producing BC is the Komagataeibacter.
Saleh and his team identified a novel BC-producing strain called Lactiplantibacillus plantarum and isolated it from rotten fruit. In experiments, this bacterium turned out to be a high-yielding one.
An emerging branch of science is ‘engineered living materials’, or ELMs. Because BCs are produced by bacteria culture, it is possible to impart desirable properties by engineering the bacteria. Research now focuses on genetic engineering of Komagataeibacter and other organisms such as Saccharomyces cerevisiae that can be co-cultured with Komagataeibacter. Scientists at the Imperial College, London, have succeeded in genetically manipulating Komagataeibacter rhaeticus.
Black dye is one of the most consumed dyes in the world, and one of the most difficult to recreate using sustainable dyeing methods. Scientists have experimented with biosynthesis of the dark melanin pigment eumelanin into Komagataeibacter rhaeticus. The experiment seems to have been a success.
In a paper that is yet to be peer-reviewed, Kenneth Walker et al say: “We demonstrate here that the production of pigmented cellulose from K. rhaeticus can be produced at large enough quantities for the prototyping of fashion products.”
They further note that their work underscores the value of genetic engineering “to design and construct strains intended to grow materials with desired properties; in this case with a chosen colour grown into the material, rather than having to be added to it later by an industrial chemical dyeing process.”
Therefore, by the looks of it, BC is emerging as a major industrial product.