A disinfectant made from sawdust mows down deadly microbes

A new, sustainable disinfectant made from sawdust and water can knock out more than 99 percent of some disease-causing microbes, including anthrax and several strains of flu.

Widespread use of some disinfectants can cause environmental harms. For instance, chlorine-containing ones, such as bleach, can form dangerous by-products when they react with other molecules (SN: 11/25/18). Some other potentially greener disinfectants rely on a compound called phenol or its chemical lookalikes, but they can be costly and energy-intensive to make.

Phenolic structures abound in wood, however, as part of the large, branching molecules that make up plant cell walls. So environmental engineer Shicheng Zhang of Fudan University in Shanghai and colleagues wondered if sawdust waste could provide a greener source of antimicrobial compounds.

The researchers cooked mixtures of water and sawdust for one hour under pressure and filtered them. Then the team tested the sawdust concoctions for their prowess at killing off the microbes Staphylococcus epidermis, a skin microbe that can cause infections in immunocompromised people, and E. coli, a gut microbe that can cause foodborne illness. Depending on a disinfectant’s concentration, it could zap more than 99 percent of the microbes, the team reports in the Jan. 18 Proceedings of the National Academy of Sciences.

The disinfectant was similarly successful at inactivating anthrax and influenza viruses, the researchers found. It may also be potent against spores, a dormant form of bacteria that can be difficult to kill. Experiments showed it could inactivate the spores of a typically harmless bacteria, Bacillus subtilis.

A chemical analysis revealed that the sawdust-based soup contains high concentrations of phenol-like compounds. The pressure cooker treatment probably breaks the wood’s molecular chains, freeing up antimicrobial phenolic molecules.

Under a microscope, the scientists saw that their disinfectant damaged the cell walls of E. coli and S. epidermis. The phenolic compounds may also damage the proteins and genetic material of bacteria and viruses, Zhang says.