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NEW species of bacteria have been discovered which can break down sodium oxalate impurities produced during the refining of bauxite into alumina.

Oxalate affects the quality of the final product. At present, refiners can either remove the oxalate and store it, which is expensive, or burn it off, but this produces large quantities of carbon dioxide. The bacteria, discovered by University of Western Australia (UWA) microbiologist Naomi McSweeney in a joint project with CSIRO and Alcoa, could offer a good alternative.

McSweeney says that oxalates are common in nature, along with the bacteria which feed on them, but the species discovered in her research have not previously been identified. Along with CSIRO and Alcoa research colleagues, she used DNA fingerprinting to identify a potentially new genus of proteobacteria, the group which includes Escherichia coli and Salmonella sp, and a new species of the known genus Halomonas.

Alcoa has constructed a bioreactor at its Kwinana bauxite refinery which uses the bacteria, capable of treating around 40 t/day of sodium oxalate. Work is ongoing to find optimal growth conditions for the bacteria, and Alcoa hopes eventually to be able to use the process in its other refineries.

"Using bacteria to break down and remove oxalate is a better, more sustainable alternative. The bacterial process breaks down the sodium oxalate and produces significantly less carbon dioxide while avoiding the need to store the impurity," says McSweeney.

The research was presented as part of Fresh Science, an Australian government initiative to identify and promote promising research by early-career scientists. tce has also reported on research to develop a silk microchip, and a polymer carbon dioxide filter, supported by Fresh Science.