Kombucha Cultures Make Excellent Sustainable Water Filters, Study Finds

Long-time Slashdot reader shoor shares a report from Ars Technica: The refreshing kombucha tea that's all the rage these days among certain global demographics might also hold the key to affordable, environmentally sustainable living membranes for water filtration, according to a recent paper published in the American Chemical Society journal ACS ES&T Water. Experiments by researchers at Montana Technological University (MTU) and Arizona State University (ASU) showed that membranes grown from kombucha cultures were better at preventing the formation of biofilms -- a significant challenge in water filtration -- than current commercial membranes.

Co-author Katherine Zodrow, an environmental engineer at MTU, led an earlier 2020 study demonstrating the feasibility of making sustainable living filtration membranes (LFMs) out of a bacterial cellulose network and the native microorganisms of a kombucha SCOBY (symbiotic culture of bacteria and yeast) culture. Zodrow and her new collaborators made their membranes for this latest round of experiments the same way: by placing a SCOBY in a growth solution of sugar, black tea, and distilled white vinegar dissolved in deionized water. The researchers then placed the mixture in a temperature-controlled room for 10-12 days until a thick membrane formed on the mixture's surface. The grown membranes were stored in deionized water and used in experiments within eight days. The 20 liters of raw water samples for the experiments were taken from the three drinking water treatment plants in Butte, Montana: Basin Creek Reservoir, Moulton Reservoir, and Big Hole River. The water samples were then pretreated in accordance with standard practices at each plant.

Both the LFMs and polymer-based filters, the researchers discovered, became clogged over time, causing them to flow and filter more slowly. The LFMs used in the experiments, however, showed between 19 and 40 percent better performance than their commercial counterparts on that score. The SCOBY-based LFMs were also more resistant to befouling. While biofilms eventually formed, fewer microorganisms were found in those films. Zodrow et al. sequenced the DNA of any bacteria and fungi in the SCOBY-based membrane and found that 97 percent of the bacteria present belonged to the genus Acetobacter. This is not surprising, since it's also the dominant bacteria in kombucha, but it may explain why the LFMs performed so well with regard to biofilms. As the name implies, a defining characteristic of this genus is the ability to oxidize organic carbon sources like sucrose, glucose, and ethanol into acetic acid, which is known for its antimicrobial properties. Acetobacter has also been shown to reduce or even remove biofilms, in keeping with the results of Zodrow et al.'s experiments.

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