Performance and bacterial community shifts during phosphogypsum biotransformation

Phosphogypsum (PG) is an industrial waste composed mainly by sulfate, turning it a suitable sulfate source for sulfate-reducing bacteria (SRB). In the present work, the capability of two SRB communities, one enriched from Portuguese PG (culture PG) and the other from sludge from a wastewater treatment plant (culture WWT-1), to use sulfate from PG was compared. In addition, the impact of this sulfate-rich waste in the microbial community was assessed. The highest efficiency in terms of sulfate reduction was observed with culture WWT-1. The bacterial composition of this culture was not significantly affected when sodium sulfate from the nutrient medium was replaced by PG as a sulfate source. Next generation sequencing (NGS) showed that this community was phylogenetically diverse, composed by bacteria affiliated to Clostridium, Arcobacter, and Sulfurospirillum genera and by SRB belonging to Desulfovibrio, Desulfomicrobium, and Desulfobulbus genera. In contrast, the bacterial structure of the community enriched from PG was modified when sodium sulfate was replaced by PG as the sulfate source. This culture, which showed the poorest performance in the use of sulfate from PG, was mainly composed by SRB related to Desulfosporosinus genus. The present work provides new information regarding the phylogenetic characterization of anaerobic bacterial communities with the ability to use PG as sulfate donor, thus, contributing to improve the knowledge of microorganisms suitable to be used in PG bioremediation. Additionally, this paper demonstrates that an alternative to lactate and low-cost carbon source (wine wastes) can be used efficiently for that purpose