Replacing rice bran with low-molecular-weight substrates affected the performance and metabolic feature of sulfate-reducing bioreactors treating acid mine drainage

Abstract

The sulfate-reducing bioreactor presents an auspicious approach for eradicating toxic metals from acid mine drainage (AMD). In earlier studies, the incorporation of rice bran as a substrate in bioreactors was observed to foster the proliferation of a diverse range of microorganisms, consequently leading to the undesirable development of biofilms atop the bioreactor. To selectively stimulate sulfate-reducing bacteria (SRB) within the bioreactor, we examined the consequences of introducing three low-molecular-weight substrates in lieu of rice bran under 12 varying conditions. The sulfate reduction performance was marginally impacted by the incorporation of lactate with corn steep liquor (CSL) compared to ethanol or glucose with CSL, and the microbial composition in the presence of lactate differed significantly from those containing ethanol or glucose. The integration of ethanol and glucose with/without CSL efficiently lowered oxidation-reduction potential and promoted the proliferation of Desulfosporosinus-related SRB (relative abundance: ∼26.6%). Given that the employment of glucose initially activated fermentative bacteria such as Clostridium spp., ethanol emerged as an efficacious alternative substrate to rice bran, which directly fosters the accumulation of Desulfosporosinus sp. without encouraging the growth of other microorganisms that contribute to the unwanted formation of biofilms within the sulfate-reducing bioreactors employed in AMD treatment.