Development of Regenerated Bacterial Cellulose Fibres from Sustainable Source

Cellulose is the most abundant organic polymer found in nature. It can be widely found in plants, or can be produced by bacteria. Cotton and wood are two common cellulose-rich raw materials which are used to produce regenerated cellulose fibres for textile applications.

However, cotton farming requires substantial amounts of pesticides and water, while the production of wood-based regenerated cellulose fibres, such as viscose fibres, also involves the use of environmentally harmful chemicals like hydrogen sulphide (H₂S) or carbon disulphide (CS₂). Addressing these issues, The Hong Kong Research Institute of Textiles and Apparel (HKRITA) has utilised the bacterial cellulose (BC) derived from the fermentation of kombucha and developed a new solvent system to produce regenerated cellulose fibres.

Turning Food Waste into Useful Textile Fibres to Mitigate Environmental Impact

Kombucha tea is a fermented sweetened black tea produced by a symbiotic culture of bacteria and yeast (SCOBY). The SCOBY waste, a gelatinous BC pellicle, is usually disposed of after beverage production. In this project, this pellicle is collected and recycled as the raw material to produce regenerated cellulose fibres.

The production processes involve purification, drying, grinding, dissolution, and spinning. First, the BC pellicle is completely immerged in a specially prepared aqueous solution to remove the unwanted residual medium and other impurities. The clean and white film is then dried by vacuum oven heating or freeze drying. The dried cellulose is shredded into small pieces and ground into fine powder for making a solution. Finally, the cellulose powder is dissolved in the new solvent system to produce a cellulose dope for spinning. Using conventional wet spinning methods, the solution is then spun into BC fibres.

The gelatinous BC pellicle produced during the fermentation of kombucha

Dried BC pellicle

Producing BC fibres using wet spinning process

Project video

 

The process of making regenerated BC fibres is more environmentally friendly than plant-based cellulose fibres production. In comparison to cotton, it takes only 10 to 14 days to ferment BC whereas cotton growth takes 150-180 days. Its water consumption is less than that of cotton farming, and it is pesticide-free. Comparing to viscose fibres, the production of BC fibres avoids deforestation and the use of environmentally harmful chemicals.

Furthermore, the project has made a successful attempt to replace refined sugar with sugar from discarded melon peels during the production of kombucha.

A New Solvent System that Overcomes Material Constraints

BC has high degrees of purity, polymerisation and crystallinity, and is thus a promising alternative for cellulose fibre production. However, these features also limit its application in the solvents and production systems available in the market. This project overcomes the challenges of a high degree of polymerisation and crystallinity by developing a novel aqueous solvent that does not involve toxic chemicals. This solvent can dissolve BC with high polymerisation levels at room temperature, reducing additional energy consumption that is needed for heating. Moreover, the solvent is 98% reusable, making the entire production process even more environmentally friendly.

This regenerated BC fibres have passed tests for fibre strength and elasticity, achieving a tensile strength comparable to viscose fibres. The research team has also successfully created dyed fibres, yarns, and sample garments. If mass-produced, these regenerated BC fibres would offer a more sustainable choice of textile material for the fashion industry.

Dyed fibres and fabrics made from the regenerated BC fibres

The sample garment has a soft hand feel and elastic texture