Poster Presentation Australian Society for Microbiology Annual Scientific Meeting 2023

Altering carbon sources impacts rare earth recovery rates during bioleaching operations on Western Australian monazite samples (#209)

Melissa Corbett 1 , Nick Fimognari 2 , Arya van Alin 2 , April Gifford 1 , Elizabeth Watkin 2
  1. Curtin Medical School , Curtin University, Perth, Western Australia, Australia
  2. School of Science, Edith Cowan University, Joondalup, WA, Australia

Interest in rare earth elements has expanded significantly over the past 15 years as these metals are crucial constituents in technological driven industries including communications, medical and defence. Western Australia’s Mt Weld mine has the world’s largest resource of rare earth elements1 and as established REE processing schemes are expensive and generate corrosive waste products, we are proposing the application of bioleaching to recover REEs from monazite as a viable alternative.

This research assessed the impact of different carbon sources on the leaching of REEs from monazite. Four heterotrophic phosphate solubilising species were selected based on our previous research2 and supplied with either galactose, maltose or fructose as a carbon source.  Klebsiella aerogenes provided with fructose released the greatest amount of total REEs (Ce, La, Nd and Pr) at 1.6 mg L-1 from 0.5g of monazite after incubation for 72 hours followed by Bukholderia T48 with 0.61 mg L-1. Meanwhile, Gluconobacter oxydans and Pseudomonas putida released REEs at much lower concentrations (< 0.2 mg L-1) regardless of the carbon source. Species provided with galactose or maltose resulted in significantly lower amounts of REEs released compared to fructose.  

HPLC analysis of the leachate detected numerous low molecular weight organic acids including gluconic, acetic, formic, malic and oxalic acid, with the largest amount detected when fructose was supplied as the carbon source for all species. In addition, acid phosphatase was detected in both the cellular and supernatant fractions in all conditions.  We hypothesize that microbially produced organic acids and acid phosphatases are responsible for REE mobilization from monazite, and carbon source selection is extremely important as the reaction is highly dependent on the biological waste products generated by the chosen species.  

This study demonstrates that assessing carbon sources in bioleaching operations is an essential step in optimizing REE recovery and paves the way to trying other carbon sources including waste products such as molasses from sugarcane or pomace from the wine industry.

  1. 1McKay, A.D., Miezitis, Y., Porritt, K., Britt, A.F., Champion, D.C., Cadman, S., . . . Carson, L. (2014). Australia's Identified Mineral Resources 2013. Geoscience Australia. Canberra, Australia
  2. 2Corbett MK; Eksteen JJ, et al. (2018) Syntrophic effect of indigenous and inoculated microorganisms in the leaching of rare earth elements from Western Australian monazite. Res Microbiol, 169 (10), 558-68.