Pseudoalteromonas lipolytica and its EPS-overproducing variant for acid mine drainage control: biofilm formation and biomineralization.

Acid mine drainage from metal sulfide tailings poses severe environmental risks. Although microbially induced carbonate precipitation (MICP) has been explored for heavy metal immobilization, the common ureolytic pathway generates harmful ammonia. This study demonstrated that Pseudoalteromonas lipolytica SCSIO 04301 and its extracellular polymeric substances (EPS)-overproducing variant effectively passivated pyrite and lead-zinc tailings via biomineralization without urea supplementation or ammonia release. Both strains formed biofilms and induced aragonite precipitation. For pyrite, passivation suppressed Fe release from ∼7500 μg/L to <60 μg/L over 180 days; leachates from passivated pyrite promoted Brassica chinensis growth to ∼100 mg fresh weight (vs. ∼53 mg for unpassivated controls). For tailings, both strains reduced total soluble metals (Fe+Al+Pb+Zn) to ≤45 μg/L, and leachates promoted plant growth to 93-121 mg. On pyrite, the EPS-overproducing variant formed a smoother, more uniform coating faster than the wild-type strain, which correlated with greater suppression of surface oxidation. On tailings, the wild-type strain formed large aggregates while the variant encapsulated individual particles; both achieved comparable passivation, but the variant showed higher susceptibility to heavy metal stress. Marine calcifying bacteria thus offer an environmentally benign alternative to ureolytic MICP for metal sulfide passivation, avoiding secondary ammonia pollution.