Random mutagenesis using cold atmospheric plasma to produce mutant microalgae for hyper-recovery of rare earth elements from mining materials

• The mutant microalgae recover up to 3 times more REEs than the wild type. • The mutant trait of microalgae is stable for 3 cycles. • Metabolomic products of mutant microalgae are lower than the wild type. • Excited N 2 *, N 2 + and O species are the main cause for microalgae mutagenesis. Random mutagenesis of microalgae offers a novel solution to improve the biomining efficiency of rare earth elements (REEs). Cold atmospheric plasma is an emerging technology to mutate microalgae strains randomly and enhance their performance. This study aims to (i) investigate the performance of mutant microalgae Chlorella vulgaris for REEs recovery, (ii) assess the stability of mutant traits at different scales, (iii) examine the metabolomic profile of the mutant C. vulgaris , and (iv) explore the potential mechanism behind cold atmospheric plasma mutagenesis. The results show that microalgae mutants exposed to cold atmospheric plasma can recover up to 3 times more REEs from bauxite than the wild type. In the leachate of clay-hosted REEs, mutant microalgae can recover 7 to 25 % more REEs than the wild type. At the bench scale, mutant strains are stable in tissue culture flasks for 3 cycles. Metabolomic analysis shows that most of the pigment, total lipid and fatty acid methyl ester (FAME) produced by mutant microalgae are lower than the wild type from 10 % to 55 %, except methyl arachidate (C20:0) and trans -9-elaidic acid methyl ester (C18:1). The optical emission spectra from plasma discharge shows that plasma discharge consists of excited N 2 *, N 2 + and O species, which might cause microalgae mutagenesis.