'From Lab Marvel To Global Guardian': Bacterial Cellulose Could Help Tackle Hazardous Substances In Europe's Waters

Issue 637: Bacterial cellulose, a biodegradable material produced by bacteria, could have “transformative potential” in remediating water contaminated by hazardous substances, according to a new review.

Water quality is a global concern; in Europe, only 37% of surface waters are in a healthy ecological state, and treating wastewater to remove hazardous pollutants is an ongoing challenge. The most high-profile risks are from substances including per- and polyfluoroalkyl substances (PFAS), nanoplastics, and endocrine-disrupting chemicals (EDCs). Such contamination is a highly topical issue in environmental and public health, with a considerable body of research now illustrating the risks and persistence of these substances.

Action on water pollution at European Union level falls under a number of policy instruments, including the Water Framework Directive, Drinking Water Directive, Urban Wastewater Treatment Directive, Zero Pollution Action Plan, and Water Resilience Strategy. The Water Resilience Strategy recognises water as a basic need and critical resource. It aims to restore and protect the water cycle; build a water-smart economy; and ensure access to clean and affordable water for all. Regulation on the registration, evaluation, authorisation and restriction of chemicals (REACH), meanwhile, is the EU’s key instrument to control the use of chemicals that pose risks, for example banning the EDC bisphenol A (BPA) in consumer products.

Effective approaches for mitigating water contamination are still being sought. Existing methods include the use of activated carbon to absorb pollutants, ion exchange – where resin beads are employed to replace harmful contaminants with harmless ions – and membrane filtration. However, these approaches fall short of what is required; for example, activated carbon has a 50-70% efficiency at removing some PFAS. They are also costly, non-selective, and produce secondary waste streams.

A narrative review has explored research on bacterial cellulose (BC), a biodegradable complex carbohydrate produced by Komagataeibacter bacteria. It aimed to address the fact that although the substance has been shown to be effective against heavy metals, dyes and microplastics, its efficacy on PFAS, EDCs and nanoplastics is yet to be explored.

Research suggests that BC can remove 90-98% of PFAS, 90-95% of EDCs and 80-90% of nanoplastics from water sources. It has different modes of action against these contaminants, enabled by its qualities of high surface area, mechanical strength and adjustable chemistry:

• PFAS removal takes place through adsorption (where contaminant molecules adhere to BC’s surface) and photodegradation (where chemicals are broken down by UV light).
• Nanoplastics removal occurs through adsorption and physical entrapment.
• EDC removal works through adsorption, size exclusion (cellulose membranes filtering larger particles) and biodegradation into non-toxic particles.

Modifying bacterial cellulose and combining it with other chemicals can increase its efficiency. For example, modified carboxymethylated BC allows effective binding for adsorption of PFAS; graphene oxide-bacterial cellulose enhances entrapment of nanoplastics through increased surface area; and microbe-immobilised BC helps bring about biodegradation of EDCs like tetracycline and BPA. Hybrid systems, for instance using BC as part of nanofiltration and electro-oxidation approaches, can boost contaminant removal efficiency by 95%.

The review also highlights that using BC in water treatment can align with circular economy principles, as the cellulose can be produced from agricultural waste feedstocks. Using waste products such as molasses, corn stover (waste biomass) and fruit peels can significantly reduce the costs of producing BC and avoid reliance on conventional carbon intensive feedstocks such as glucose.

The review calls for a full lifecycle assessment and testing protocols that align with International Organization for Standardization (ISO) standards to evaluate the adsorption capacity, toxicity and reusability of BC. There is also a need for regulatory alignment with REACH by meeting maximum contaminant levels for key pollutants, as well as relevant international certifications for aspects such as biodegradability and biocompatibility.

To bring BC into mainstream use in water treatment, the work also calls for new collaborations between regulators, academia and industry, funding support such as through the EU’s Horizon Europe programme, and real-world pilot scale studies to assess scalability and durability. According to the review author, continued optimisations could “propel BC from lab marvel to global guardian of pristine waters”.