Enhanced biological desilication by Bacillus mucilaginosus mutant: Multi-omics insights into extracellular polymeric substance overproduction and metabolic adaptations.
Recovering scandium from silicate-rich tailings remains a major challenge due to refractory mineral matrices. Although biological desilication using microbial secretomes offers an eco-friendly solution, its industrial application is limited by the poor understanding of the intracellular metabolic programs that govern high-efficiency desilication. Here, an N-methyl-N'-nitro-N-nitrosoguanidine (NTG)-induced Bacillus mucilaginosus mutant, BM3, was evaluated using integrated whole-genome sequencing, transcriptomics, non-targeted metabolomics and mineral-interface measurements. BM3 achieved a 1.7-fold increase in desilication rate and subsequent chemical leaching of the bio-pretreated tailings substantially elevated scandium extraction from 21% (untreated) and 38% (wild-type-pretreated) to 53%. Spectroscopic analyses indicated that this modified secretome acted as a reactive interface, preferentially eroding recalcitrant pyroxene phases via carboxyl, amino, and hydroxyl ligand coordination. Multi-omics integration suggested that a coordinated metabolic reprogramming, including changes in phenylalanine metabolism, purine metabolism, and folate one-carbon metabolism, may underpin this phenotype. Overall, these findings reveal that the enhanced desilication by BM3 is associated with coordinated metabolic reprogramming and a more reactive EPS-mineral interface, providing an effective biological pretreatment for disrupting silicate matrices and improving scandium recovery from refractory tailings.