Effect of alkaline leaching of phosphogypsum on sulfate reduction activity and bacterial community composition using different sources of anaerobic microbial inoculum

Exploring the biodegradation activity of Priestia aryabhattai 1-3I, a promising chlorpyrifos-degrading strain isolated from a local phosphogypsum landfill

The current study emphasizes the potential of the microbial community within phosphogypsum landfills to identify promising microorganisms involved in Chlorpyrifos (CP) biodegradation, an organophosphorus pesticide extensively employed in the agricultural sector. We isolated 26 bacterial strains from CP-enriched phosphogypsum sample contaminated with 100 mg Kg-1 CP and subsequently identified them through 16S rRNA sequencing. Among these isolates, Priestia aryabhattai 1-3I displayed remarkable proficiency in utilizing CP as a sole carbon source. Furthermore, P. aryabhattai 1-3I was found to harbor an oph-encoding gene, a crucial component in the CP degradation pathway, with a highly conserved 694 bp region shared by at least 24 homologous oph bacterial genes. The CP-degrading ability of P. aryabhattai 1-3I was assessed both in liquid medium and soil samples, achieving degradation rates of 95 % and 60 %, respectively, starting from an initial concentration of 100 mg L-1 CP after 4 weeks. This pronounced CP-degrading activity correlated with a rapid and significant increase in oph transcripts and was accompanied by a notable rise in the accumulation of a major protein band with a molecular weight of 39 kDa, consistent with the molecular weight of previously characterized oph proteins. Of particular interest, the toxicity of CP degradation products resulting from both CP-bacterial biodegradation experiments exhibited minimal effects on neural cells, as indicated by acetylcholinesterase (AChE) activity and cell viability, underscoring the safety of CP-metabilties. Our study underscores the exceptional biodegradation capability of P. aryabhattai 1-3I in breaking down CP in soil, highlighting its potential for effective remediation of CP-contaminated environments.

Impact of Phosphogypsum on Viability of Trichuris suis Eggs in Anaerobic Digestion of Swine Manure

Waste from livestock farms contains various pathogens, including eggs and larvae of helminths-pathogens of parasitic diseases harmful to animals and humans. One of the methods for their effective processing to obtain biofertilizer and biofuel is anaerobic digestion, which requires further improvement to completely suppress the viability of pathogenic microorganisms in mesophilic conditions. To this end, the use of anaerobic digestion under sulfate reduction conditions to suppress pathogens using biogenic hydrogen sulfide is promising. Consequently, this study aims to study the effect of a sulfur-containing additive such as phosphogypsum on the disinfection of pig manure during anaerobic digestion. Egg mortality was already found to increase significantly compared to the control (80% and more), even at a minimum concentration of phosphogypsum (5%), on the fifth day of the experiment. At the same time, the maximum effect (100% mortality of Trichuris suis eggs) was recorded at a 10% concentration of phosphogypsum, starting from the 10th day of the study. Our experiment showed that changes in anaerobic digestion conditions using phosphogypsum could positively affect digestate disinfection. However, further research is needed to optimize the conditions of the process for an effective combination of disinfection with the production of environmentally safe organic fertilizers and high-quality biogas with a high level of methane.

Impact of steel slag, gypsum, and coal gangue on microbial immobilization of metal(loid)s in non-ferrous mine waste dumps

Non-ferrous mine waste dumps globally generate soil pollution characterized by low pH and high metal(loid)s content. In this study, the steel slag (SS), gypsum (G), and coal gangue (CG) combined with functional bacteria consortium (FB23) were used for immobilizing metal(loid)s in the soil. The result shown that FB23 can effectively decrease As, Pb, and Zn concentrations within 10 d in an aqueous medium experiment. In a 310-day field column experiment, solid waste including SS, G, and CG combined with FB23 decreased As, Cd, Cu, and Pb concentrations in the aqueous phase. Optimized treatment was obtained by combining FB23 with 1% SS, 1% G, and 1.5% CG. Furthermore, the application of solid waste (SS, G, and CG) increased the top 20 functional bacterial consortium (FB23) abundance at the genus level from 1% to 21% over 50 days in the soil waste dump. Moreover, dissolved organic carbon (DOC) and pH were identified as the main factors influencing the reduction in bioavailable As, Cd, Cu, and Pb in the combination remediation. Additionally, the reduction of Fe and sulfur S was crucial for decreasing the mobilization of the metal(loid)s. This study provides valuable insights into the remediation of metal contamination on a larger scale.